- 04 Feb, 2022 1 commit
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Jim Mattson authored
CPUID.(EAX=7,ECX=0):EBX.FDP_EXCPTN_ONLY[bit 6] and CPUID.(EAX=7,ECX=0):EBX.ZERO_FCS_FDS[bit 13] are "defeature" bits. Unlike most of the other CPUID feature bits, these bits are clear if the features are present and set if the features are not present. These bits should be reported in KVM_GET_SUPPORTED_CPUID, because if these bits are set on hardware, they cannot be cleared in the guest CPUID. Doing so would claim guest support for a feature that the hardware doesn't support and that can't be efficiently emulated. Of course, any software (e.g WIN87EM.DLL) expecting these features to be present likely predates these CPUID feature bits and therefore doesn't know to check for them anyway. Aaron Lewis added the corresponding X86_FEATURE macros in commit cbb99c0f ("x86/cpufeatures: Add FDP_EXCPTN_ONLY and ZERO_FCS_FDS"), with the intention of reporting these bits in KVM_GET_SUPPORTED_CPUID, but I was unable to find a proposed patch on the kvm list. Opportunistically reordered the CPUID_7_0_EBX capability bits from least to most significant. Cc: Aaron Lewis <aaronlewis@google.com> Signed-off-by:
Jim Mattson <jmattson@google.com> Message-Id: <20220204001348.2844660-1-jmattson@google.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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- 02 Feb, 2022 4 commits
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https://github.com/kvm-riscv/linuxPaolo Bonzini authored
KVM/riscv fixes for 5.17, take #1 - Rework guest entry logic - Make CY, TM, and IR counters accessible in VU mode - Fix SBI implementation version
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Anup Patel authored
The SBI implementation version returned by KVM RISC-V should be the Host Linux version code. Fixes: c62a7685 ("RISC-V: KVM: Add SBI v0.2 base extension") Signed-off-by:
Anup Patel <apatel@ventanamicro.com> Reviewed-by:
Atish Patra <atishp@rivosinc.com> Signed-off-by:
Anup Patel <anup@brainfault.org>
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Mayuresh Chitale authored
Those applications that run in VU mode and access the time CSR cause a virtual instruction trap as Guest kernel currently does not initialize the scounteren CSR. To fix this, we should make CY, TM, and IR counters accessibile by default in VU mode (similar to OpenSBI). Fixes: a33c72fa ("RISC-V: KVM: Implement VCPU create, init and destroy functions") Cc: stable@vger.kernel.org Signed-off-by:
Mayuresh Chitale <mchitale@ventanamicro.com> Signed-off-by:
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Mark Rutland authored
In kvm_arch_vcpu_ioctl_run() we enter an RCU extended quiescent state (EQS) by calling guest_enter_irqoff(), and unmask IRQs prior to exiting the EQS by calling guest_exit(). As the IRQ entry code will not wake RCU in this case, we may run the core IRQ code and IRQ handler without RCU watching, leading to various potential problems. Additionally, we do not inform lockdep or tracing that interrupts will be enabled during guest execution, which caan lead to misleading traces and warnings that interrupts have been enabled for overly-long periods. This patch fixes these issues by using the new timing and context entry/exit helpers to ensure that interrupts are handled during guest vtime but with RCU watching, with a sequence: guest_timing_enter_irqoff(); guest_state_enter_irqoff(); < run the vcpu > guest_state_exit_irqoff(); < take any pending IRQs > guest_timing_exit_irqoff(); Since instrumentation may make use of RCU, we must also ensure that no instrumented code is run during the EQS. I've split out the critical section into a new kvm_riscv_enter_exit_vcpu() helper which is marked noinstr. Fixes: 99cdc6c1 ("RISC-V: Add initial skeletal KVM support") Signed-off-by:
Mark Rutland <mark.rutland@arm.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Anup Patel <anup@brainfault.org> Cc: Atish Patra <atishp@atishpatra.org> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Paul Walmsley <paul.walmsley@sifive.com> Tested-by:
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- 01 Feb, 2022 5 commits
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Mark Rutland authored
In kvm_arch_vcpu_ioctl_run() we enter an RCU extended quiescent state (EQS) by calling guest_enter_irqoff(), and unmasked IRQs prior to exiting the EQS by calling guest_exit(). As the IRQ entry code will not wake RCU in this case, we may run the core IRQ code and IRQ handler without RCU watching, leading to various potential problems. Additionally, we do not inform lockdep or tracing that interrupts will be enabled during guest execution, which caan lead to misleading traces and warnings that interrupts have been enabled for overly-long periods. This patch fixes these issues by using the new timing and context entry/exit helpers to ensure that interrupts are handled during guest vtime but with RCU watching, with a sequence: guest_timing_enter_irqoff(); guest_state_enter_irqoff(); < run the vcpu > guest_state_exit_irqoff(); < take any pending IRQs > guest_timing_exit_irqoff(); Since instrumentation may make use of RCU, we must also ensure that no instrumented code is run during the EQS. I've split out the critical section into a new kvm_arm_enter_exit_vcpu() helper which is marked noinstr. Fixes: 1b3d546d ("arm/arm64: KVM: Properly account for guest CPU time") Reported-by:
Nicolas Saenz Julienne <nsaenzju@redhat.com> Signed-off-by:
Marc Zyngier <maz@kernel.org> Reviewed-by:
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Mark Rutland authored
For consistency and clarity, migrate x86 over to the generic helpers for guest timing and lockdep/RCU/tracing management, and remove the x86-specific helpers. Prior to this patch, the guest timing was entered in kvm_guest_enter_irqoff() (called by svm_vcpu_enter_exit() and svm_vcpu_enter_exit()), and was exited by the call to vtime_account_guest_exit() within vcpu_enter_guest(). To minimize duplication and to more clearly balance entry and exit, both entry and exit of guest timing are placed in vcpu_enter_guest(), using the new guest_timing_{enter,exit}_irqoff() helpers. When context tracking is used a small amount of additional time will be accounted towards guests; tick-based accounting is unnaffected as IRQs are disabled at this point and not enabled until after the return from the guest. This also corrects (benign) mis-balanced context tracking accounting introduced in commits: ae95f566 ("KVM: X86: TSCDEADLINE MSR emulation fastpath") 26efe2fd ("KVM: VMX: Handle preemption timer fastpath") Where KVM can enter a guest multiple times, calling vtime_guest_enter() without a corresponding call to vtime_account_guest_exit(), and with vtime_account_system() called when vtime_account_guest() should be used. As account_system_time() checks PF_VCPU and calls account_guest_time(), this doesn't result in any functional problem, but is unnecessarily confusing. Signed-off-by: -
Mark Rutland authored
In kvm_arch_vcpu_ioctl_run() we use guest_enter_irqoff() and guest_exit_irqoff() directly, with interrupts masked between these. As we don't handle any timer ticks during this window, we will not account time spent within the guest as guest time, which is unfortunate. Additionally, we do not inform lockdep or tracing that interrupts will be enabled during guest execution, which caan lead to misleading traces and warnings that interrupts have been enabled for overly-long periods. This patch fixes these issues by using the new timing and context entry/exit helpers to ensure that interrupts are handled during guest vtime but with RCU watching, with a sequence: guest_timing_enter_irqoff(); guest_state_enter_irqoff(); < run the vcpu > guest_state_exit_irqoff(); < take any pending IRQs > guest_timing_exit_irqoff(); In addition, as guest exits during the "run the vcpu" step are handled by kvm_mips_handle_exit(), a wrapper function is added which ensures that such exists are handled with a sequence: guest_state_exit_irqoff(); < handle the exit > guest_state_enter_irqoff(); This means that exits which stop the vCPU running will have a redundant guest_state_enter_irqoff() .. guest_state_exit_irqoff() sequence, which can be addressed with future rework. Since instrumentation may make use of RCU, we must also ensure that no instrumented code is run during the EQS. I've split out the critical section into a new kvm_mips_enter_exit_vcpu() helper which is marked noinstr. Signed-off-by:
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Mark Rutland authored
When transitioning to/from guest mode, it is necessary to inform lockdep, tracing, and RCU in a specific order, similar to the requirements for transitions to/from user mode. Additionally, it is necessary to perform vtime accounting for a window around running the guest, with RCU enabled, such that timer interrupts taken from the guest can be accounted as guest time. Most architectures don't handle all the necessary pieces, and a have a number of common bugs, including unsafe usage of RCU during the window between guest_enter() and guest_exit(). On x86, this was dealt with across commits: 87fa7f3e ("x86/kvm: Move context tracking where it belongs") 0642391e ("x86/kvm/vmx: Add hardirq tracing to guest enter/exit") 9fc975e9 ("x86/kvm/svm: Add hardirq tracing on guest enter/exit") 3ebccdf3 ("x86/kvm/vmx: Move guest enter/exit into .noinstr.text") 135961e0 ("x86/kvm/svm: Move guest enter/exit into .noinstr.text") 16045714 ("KVM: x86: Defer vtime accounting 'til after IRQ handling") bc908e09 ("KVM: x86: Consolidate guest enter/exit logic to common helpers") ... but those fixes are specific to x86, and as the resulting logic (while correct) is split across generic helper functions and x86-specific helper functions, it is difficult to see that the entry/exit accounting is balanced. This patch adds generic helpers which architectures can use to handle guest entry/exit consistently and correctly. The guest_{enter,exit}() helpers are split into guest_timing_{enter,exit}() to perform vtime accounting, and guest_context_{enter,exit}() to perform the necessary context tracking and RCU management. The existing guest_{enter,exit}() heleprs are left as wrappers of these. Atop this, new guest_state_enter_irqoff() and guest_state_exit_irqoff() helpers are added to handle the ordering of lockdep, tracing, and RCU manageent. These are inteneded to mirror exit_to_user_mode() and enter_from_user_mode(). Subsequent patches will migrate architectures over to the new helpers, following a sequence: guest_timing_enter_irqoff(); guest_state_enter_irqoff(); < run the vcpu > guest_state_exit_irqoff(); < take any pending IRQs > guest_timing_exit_irqoff(); This sequences handles all of the above correctly, and more clearly balances the entry and exit portions, making it easier to understand. The existing helpers are marked as deprecated, and will be removed once all architectures have been converted. There should be no functional change as a result of this patch. Signed-off-by:
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Sean Christopherson authored
Handle non-APICv interrupt delivery in vendor code, even though it means VMX and SVM will temporarily have duplicate code. SVM's AVIC has a race condition that requires KVM to fall back to legacy interrupt injection _after_ the interrupt has been logged in the vIRR, i.e. to fix the race, SVM will need to open code the full flow anyways[*]. Refactor the code so that the SVM bug without introducing other issues, e.g. SVM would return "success" and thus invoke trace_kvm_apicv_accept_irq() even when delivery through the AVIC failed, and to opportunistically prepare for using KVM_X86_OP to fill each vendor's kvm_x86_ops struct, which will rely on the vendor function matching the kvm_x86_op pointer name. No functional change intended. [*] https://lore.kernel.org/all/20211213104634.199141-4-mlevitsk@redhat.comSigned-off-by:
Sean Christopherson <seanjc@google.com> Message-Id: <20220128005208.4008533-3-seanjc@google.com> Signed-off-by:
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- 31 Jan, 2022 1 commit
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Janosch Frank authored
This way we can more easily find the next free IOCTL number when adding new IOCTLs. Fixes: be50b206 ("kvm: x86: Add support for getting/setting expanded xstate buffer") Signed-off-by:
Janosch Frank <frankja@linux.ibm.com> Message-Id: <20220128154025.102666-1-frankja@linux.ibm.com> Signed-off-by:
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- 28 Jan, 2022 10 commits
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Paolo Bonzini authored
Merge tag 'kvmarm-fixes-5.17-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD KVM/arm64 fixes for 5.17, take #1 - Correctly update the shadow register on exception injection when running in nVHE mode - Correctly use the mm_ops indirection when performing cache invalidation from the page-table walker - Restrict the vgic-v3 workaround for SEIS to the two known broken implementations
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Hou Wenlong authored
Fix the following false positive warning: ============================= WARNING: suspicious RCU usage 5.16.0-rc4+ #57 Not tainted ----------------------------- arch/x86/kvm/../../../virt/kvm/eventfd.c:484 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 3 locks held by fc_vcpu 0/330: #0: ffff8884835fc0b0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x88/0x6f0 [kvm] #1: ffffc90004c0bb68 (&kvm->srcu){....}-{0:0}, at: vcpu_enter_guest+0x600/0x1860 [kvm] #2: ffffc90004c0c1d0 (&kvm->irq_srcu){....}-{0:0}, at: kvm_notify_acked_irq+0x36/0x180 [kvm] stack backtrace: CPU: 26 PID: 330 Comm: fc_vcpu 0 Not tainted 5.16.0-rc4+ Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x44/0x57 kvm_notify_acked_gsi+0x6b/0x70 [kvm] kvm_notify_acked_irq+0x8d/0x180 [kvm] kvm_ioapic_update_eoi+0x92/0x240 [kvm] kvm_apic_set_eoi_accelerated+0x2a/0xe0 [kvm] handle_apic_eoi_induced+0x3d/0x60 [kvm_intel] vmx_handle_exit+0x19c/0x6a0 [kvm_intel] vcpu_enter_guest+0x66e/0x1860 [kvm] kvm_arch_vcpu_ioctl_run+0x438/0x7f0 [kvm] kvm_vcpu_ioctl+0x38a/0x6f0 [kvm] __x64_sys_ioctl+0x89/0xc0 do_syscall_64+0x3a/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae Since kvm_unregister_irq_ack_notifier() does synchronize_srcu(&kvm->irq_srcu), kvm->irq_ack_notifier_list is protected by kvm->irq_srcu. In fact, kvm->irq_srcu SRCU read lock is held in kvm_notify_acked_irq(), making it a false positive warning. So use hlist_for_each_entry_srcu() instead of hlist_for_each_entry_rcu(). Reviewed-by:Hou Wenlong <houwenlong93@linux.alibaba.com> Message-Id: <f98bac4f5052bad2c26df9ad50f7019e40434512.1643265976.git.houwenlong.hwl@antgroup.com> Signed-off-by:
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Vitaly Kuznetsov authored
Hyper-V TLFS explicitly forbids VMREAD and VMWRITE instructions when Enlightened VMCS interface is in use: "Any VMREAD or VMWRITE instructions while an enlightened VMCS is active is unsupported and can result in unexpected behavior."" Windows 11 + WSL2 seems to ignore this, attempts to VMREAD VMCS field 0x4404 ("VM-exit interruption information") are observed. Failing these attempts with nested_vmx_failInvalid() makes such guests unbootable. Microsoft confirms this is a Hyper-V bug and claims that it'll get fixed eventually but for the time being we need a workaround. (Temporary) allow VMREAD to get data from the currently loaded Enlightened VMCS. Note: VMWRITE instructions remain forbidden, it is not clear how to handle them properly and hopefully won't ever be needed. Reviewed-by:Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20220112170134.1904308-6-vkuznets@redhat.com> Signed-off-by:
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Vitaly Kuznetsov authored
In preparation to allowing reads from Enlightened VMCS from handle_vmread(), implement evmcs_field_offset() to get the correct read offset. get_evmcs_offset(), which is being used by KVM-on-Hyper-V, is almost what's needed but a few things need to be adjusted. First, WARN_ON() is unacceptable for handle_vmread() as any field can (in theory) be supplied by the guest and not all fields are defined in eVMCS v1. Second, we need to handle 'holes' in eVMCS (missing fields). It also sounds like a good idea to WARN_ON() if such fields are ever accessed by KVM-on-Hyper-V. Implement dedicated evmcs_field_offset() helper. No functional change intended. Signed-off-by:
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Vitaly Kuznetsov authored
vmcs_to_field_offset{,_table} may sound misleading as VMCS is an opaque blob which is not supposed to be accessed directly. In fact, vmcs_to_field_offset{,_table} are related to KVM defined VMCS12 structure. Rename vmcs_field_to_offset() to get_vmcs12_field_offset() for clarity. No functional change intended. Reviewed-by: -
Vitaly Kuznetsov authored
Enlightened VMCS v1 doesn't have VMX_PREEMPTION_TIMER_VALUE field, PIN_BASED_VMX_PREEMPTION_TIMER is also filtered out already so it makes sense to filter out VM_EXIT_SAVE_VMX_PREEMPTION_TIMER too. Note, none of the currently existing Windows/Hyper-V versions are known to enable 'save VMX-preemption timer value' when eVMCS is in use, the change is aimed at making the filtering future proof. Signed-off-by:
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Vitaly Kuznetsov authored
Similar to MSR_IA32_VMX_EXIT_CTLS/MSR_IA32_VMX_TRUE_EXIT_CTLS, MSR_IA32_VMX_ENTRY_CTLS/MSR_IA32_VMX_TRUE_ENTRY_CTLS pair, MSR_IA32_VMX_TRUE_PINBASED_CTLS needs to be filtered the same way MSR_IA32_VMX_PINBASED_CTLS is currently filtered as guests may solely rely on 'true' MSR data. Note, none of the currently existing Windows/Hyper-V versions are known to stumble upon the unfiltered MSR_IA32_VMX_TRUE_PINBASED_CTLS, the change is aimed at making the filtering future proof. Signed-off-by:
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Paolo Bonzini authored
Provide coverage for the new API. Signed-off-by: -
Paolo Bonzini authored
Because KVM_GET_SUPPORTED_CPUID is meant to be passed (by simple-minded VMMs) to KVM_SET_CPUID2, it cannot include any dynamic xsave states that have not been enabled. Probing those, for example so that they can be passed to ARCH_REQ_XCOMP_GUEST_PERM, requires a new ioctl or arch_prctl. The latter is in fact worse, even though that is what the rest of the API uses, because it would require supported_xcr0 to be moved from the KVM module to the kernel just for this use. In addition, the value would be nonsensical (or an error would have to be returned) until the KVM module is loaded in. Therefore, to limit the growth of system ioctls, add a /dev/kvm variant of KVM_{GET,HAS}_DEVICE_ATTR, and implement it in x86 with just one group (0) and attribute (KVM_X86_XCOMP_GUEST_SUPP). Signed-off-by: -
Sean Christopherson authored
Add a helper to handle converting the u64 userspace address embedded in struct kvm_device_attr into a userspace pointer, it's all too easy to forget the intermediate "unsigned long" cast as well as the truncation check. No functional change intended. Signed-off-by:
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- 26 Jan, 2022 19 commits
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Paolo Bonzini authored
There is no need for tests other than amx_test to enable dynamic xsave states. Remove the call to vm_xsave_req_perm from generic code, and move it inside the test. While at it, allow customizing the bit that is requested, so that future tests can use it differently. Signed-off-by: -
Like Xu authored
XCR0 is reset to 1 by RESET but not INIT and IA32_XSS is zeroed by both RESET and INIT. The kvm_set_msr_common()'s handling of MSR_IA32_XSS also needs to update kvm_update_cpuid_runtime(). In the above cases, the size in bytes of the XSAVE area containing all states enabled by XCR0 or (XCRO | IA32_XSS) needs to be updated. For simplicity and consistency, existing helpers are used to write values and call kvm_update_cpuid_runtime(), and it's not exactly a fast path. Fixes: a554d207 ("KVM: X86: Processor States following Reset or INIT") Cc: stable@vger.kernel.org Signed-off-by:
Like Xu <likexu@tencent.com> Signed-off-by:
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Like Xu authored
Do a runtime CPUID update for a vCPU if MSR_IA32_XSS is written, as the size in bytes of the XSAVE area is affected by the states enabled in XSS. Fixes: 20300099 ("kvm: vmx: add MSR logic for XSAVES") Cc: stable@vger.kernel.org Signed-off-by:
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Xiaoyao Li authored
It has been corrected from SDM version 075 that MSR_IA32_XSS is reset to zero on Power up and Reset but keeps unchanged on INIT. Fixes: a554d207 ("KVM: X86: Processor States following Reset or INIT") Cc: stable@vger.kernel.org Signed-off-by:
Xiaoyao Li <xiaoyao.li@intel.com> Signed-off-by:
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Sean Christopherson authored
Free the "struct kvm_cpuid_entry2" array on successful post-KVM_RUN KVM_SET_CPUID{,2} to fix a memory leak, the callers of kvm_set_cpuid() free the array only on failure. BUG: memory leak unreferenced object 0xffff88810963a800 (size 2048): comm "syz-executor025", pid 3610, jiffies 4294944928 (age 8.080s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 0d 00 00 00 ................ 47 65 6e 75 6e 74 65 6c 69 6e 65 49 00 00 00 00 GenuntelineI.... backtrace: [<ffffffff814948ee>] kmalloc_node include/linux/slab.h:604 [inline] [<ffffffff814948ee>] kvmalloc_node+0x3e/0x100 mm/util.c:580 [<ffffffff814950f2>] kvmalloc include/linux/slab.h:732 [inline] [<ffffffff814950f2>] vmemdup_user+0x22/0x100 mm/util.c:199 [<ffffffff8109f5ff>] kvm_vcpu_ioctl_set_cpuid2+0x8f/0xf0 arch/x86/kvm/cpuid.c:423 [<ffffffff810711b9>] kvm_arch_vcpu_ioctl+0xb99/0x1e60 arch/x86/kvm/x86.c:5251 [<ffffffff8103e92d>] kvm_vcpu_ioctl+0x4ad/0x950 arch/x86/kvm/../../../virt/kvm/kvm_main.c:4066 [<ffffffff815afacc>] vfs_ioctl fs/ioctl.c:51 [inline] [<ffffffff815afacc>] __do_sys_ioctl fs/ioctl.c:874 [inline] [<ffffffff815afacc>] __se_sys_ioctl fs/ioctl.c:860 [inline] [<ffffffff815afacc>] __x64_sys_ioctl+0xfc/0x140 fs/ioctl.c:860 [<ffffffff844a3335>] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [<ffffffff844a3335>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 [<ffffffff84600068>] entry_SYSCALL_64_after_hwframe+0x44/0xae Fixes: c6617c61 ("KVM: x86: Partially allow KVM_SET_CPUID{,2} after KVM_RUN") Cc: stable@vger.kernel.org Reported-by: syzbot+be576ad7655690586eec@syzkaller.appspotmail.com Signed-off-by: -
Sean Christopherson authored
WARN if KVM attempts to allocate a shadow VMCS for vmcs02. KVM emulates VMCS shadowing but doesn't virtualize it, i.e. KVM should never allocate a "real" shadow VMCS for L2. The previous code WARNed but continued anyway with the allocation, presumably in an attempt to avoid NULL pointer dereference. However, alloc_vmcs (and hence alloc_shadow_vmcs) can fail, and indeed the sole caller does: if (enable_shadow_vmcs && !alloc_shadow_vmcs(vcpu)) goto out_shadow_vmcs; which makes it not a useful attempt. Signed-off-by:
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Sean Christopherson authored
Don't skip the vmcall() in l2_guest_code() prior to re-entering L2, doing so will result in L2 running to completion, popping '0' off the stack for RET, jumping to address '0', and ultimately dying with a triple fault shutdown. It's not at all obvious why the test re-enters L2 and re-executes VMCALL, but presumably it serves a purpose. The VMX path doesn't skip vmcall(), and the test can't possibly have passed on SVM, so just do what VMX does. Fixes: d951b221 ("KVM: selftests: smm_test: Test SMM enter from L2") Cc: Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by:
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Vitaly Kuznetsov authored
kvm_cpuid_check_equal() checks for the (full) equality of the supplied CPUID data so .flags need to be checked too. Reported-by:
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Sean Christopherson authored
Forcibly leave nested virtualization operation if userspace toggles SMM state via KVM_SET_VCPU_EVENTS or KVM_SYNC_X86_EVENTS. If userspace forces the vCPU out of SMM while it's post-VMXON and then injects an SMI, vmx_enter_smm() will overwrite vmx->nested.smm.vmxon and end up with both vmxon=false and smm.vmxon=false, but all other nVMX state allocated. Don't attempt to gracefully handle the transition as (a) most transitions are nonsencial, e.g. forcing SMM while L2 is running, (b) there isn't sufficient information to handle all transitions, e.g. SVM wants access to the SMRAM save state, and (c) KVM_SET_VCPU_EVENTS must precede KVM_SET_NESTED_STATE during state restore as the latter disallows putting the vCPU into L2 if SMM is active, and disallows tagging the vCPU as being post-VMXON in SMM if SMM is not active. Abuse of KVM_SET_VCPU_EVENTS manifests as a WARN and memory leak in nVMX due to failure to free vmcs01's shadow VMCS, but the bug goes far beyond just a memory leak, e.g. toggling SMM on while L2 is active puts the vCPU in an architecturally impossible state. WARNING: CPU: 0 PID: 3606 at free_loaded_vmcs arch/x86/kvm/vmx/vmx.c:2665 [inline] WARNING: CPU: 0 PID: 3606 at free_loaded_vmcs+0x158/0x1a0 arch/x86/kvm/vmx/vmx.c:2656 Modules linked in: CPU: 1 PID: 3606 Comm: syz-executor725 Not tainted 5.17.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:free_loaded_vmcs arch/x86/kvm/vmx/vmx.c:2665 [inline] RIP: 0010:free_loaded_vmcs+0x158/0x1a0 arch/x86/kvm/vmx/vmx.c:2656 Code: <0f> 0b eb b3 e8 8f 4d 9f 00 e9 f7 fe ff ff 48 89 df e8 92 4d 9f 00 Call Trace: <TASK> kvm_arch_vcpu_destroy+0x72/0x2f0 arch/x86/kvm/x86.c:11123 kvm_vcpu_destroy arch/x86/kvm/../../../virt/kvm/kvm_main.c:441 [inline] kvm_destroy_vcpus+0x11f/0x290 arch/x86/kvm/../../../virt/kvm/kvm_main.c:460 kvm_free_vcpus arch/x86/kvm/x86.c:11564 [inline] kvm_arch_destroy_vm+0x2e8/0x470 arch/x86/kvm/x86.c:11676 kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:1217 [inline] kvm_put_kvm+0x4fa/0xb00 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1250 kvm_vm_release+0x3f/0x50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1273 __fput+0x286/0x9f0 fs/file_table.c:311 task_work_run+0xdd/0x1a0 kernel/task_work.c:164 exit_task_work include/linux/task_work.h:32 [inline] do_exit+0xb29/0x2a30 kernel/exit.c:806 do_group_exit+0xd2/0x2f0 kernel/exit.c:935 get_signal+0x4b0/0x28c0 kernel/signal.c:2862 arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868 handle_signal_work kernel/entry/common.c:148 [inline] exit_to_user_mode_loop kernel/entry/common.c:172 [inline] exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline] syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x44/0xae </TASK> Cc: stable@vger.kernel.org Reported-by: syzbot+8112db3ab20e70d50c31@syzkaller.appspotmail.com Signed-off-by:
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Vitaly Kuznetsov authored
Commit 3fa5e8fd ("KVM: SVM: delay svm_vcpu_init_msrpm after svm->vmcb is initialized") re-arranged svm_vcpu_init_msrpm() call in svm_create_vcpu(), thus making the comment about vmcb being NULL obsolete. Drop it. While on it, drop superfluous vmcb_is_clean() check: vmcb_mark_dirty() is a bit flip, an extra check is unlikely to bring any performance gain. Drop now-unneeded vmcb_is_clean() helper as well. Fixes: 3fa5e8fd ("KVM: SVM: delay svm_vcpu_init_msrpm after svm->vmcb is initialized") Signed-off-by:
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Vitaly Kuznetsov authored
Commit c4327f15 ("KVM: SVM: hyper-v: Enlightened MSR-Bitmap support") introduced enlightened MSR-Bitmap support for KVM-on-Hyper-V but it didn't actually enable the support. Similar to enlightened NPT TLB flush and direct TLB flush features, the guest (KVM) has to tell L0 (Hyper-V) that it's using the feature by setting the appropriate feature fit in VMCB control area (sw reserved fields). Fixes: c4327f15 ("KVM: SVM: hyper-v: Enlightened MSR-Bitmap support") Signed-off-by:
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Sean Christopherson authored
Inject a #GP instead of synthesizing triple fault to try to avoid killing the guest if emulation of an SEV guest fails due to encountering the SMAP erratum. The injected #GP may still be fatal to the guest, e.g. if the userspace process is providing critical functionality, but KVM should make every attempt to keep the guest alive. Signed-off-by:
Liam Merwick <liam.merwick@oracle.com> Message-Id: <20220120010719.711476-10-seanjc@google.com> Signed-off-by:
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Sean Christopherson authored
Resume the guest instead of synthesizing a triple fault shutdown if the instruction bytes buffer is empty due to the #NPF being on the code fetch itself or on a page table access. The SMAP errata applies if and only if the code fetch was successful and ucode's subsequent data read from the code page encountered a SMAP violation. In practice, the guest is likely hosed either way, but crashing the guest on a code fetch to emulated MMIO is technically wrong according to the behavior described in the APM. Signed-off-by:
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Sean Christopherson authored
Inject #UD if KVM attempts emulation for an SEV guests without an insn buffer and instruction decoding is required. The previous behavior of allowing emulation if there is no insn buffer is undesirable as doing so means KVM is reading guest private memory and thus decoding cyphertext, i.e. is emulating garbage. The check was previously necessary as the emulation type was not provided, i.e. SVM needed to allow emulation to handle completion of emulation after exiting to userspace to handle I/O. Signed-off-by:
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Sean Christopherson authored
WARN if KVM attempts to emulate in response to #UD or #GP for SEV guests, i.e. if KVM intercepts #UD or #GP, as emulation on any fault except #NPF is impossible since KVM cannot read guest private memory to get the code stream, and the CPU's DecodeAssists feature only provides the instruction bytes on #NPF. Signed-off-by:
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Sean Christopherson authored
Pass the emulation type to kvm_x86_ops.can_emulate_insutrction() so that a future commit can harden KVM's SEV support to WARN on emulation scenarios that should never happen. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Add a sanity check on DECODEASSIST being support if SEV is supported, as KVM cannot read guest private memory and thus relies on the CPU to provide the instruction byte stream on #NPF for emulation. The intent of the check is to document the dependency, it should never fail in practice as producing hardware that supports SEV but not DECODEASSISTS would be non-sensical. Signed-off-by:
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Sean Christopherson authored
Never intercept #GP for SEV guests as reading SEV guest private memory will return cyphertext, i.e. emulating on #GP can't work as intended. Cc: stable@vger.kernel.org Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: Brijesh Singh <brijesh.singh@amd.com> Signed-off-by:
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Sean Christopherson authored
Revert a completely broken check on an "invalid" RIP in SVM's workaround for the DecodeAssists SMAP errata. kvm_vcpu_gfn_to_memslot() obviously expects a gfn, i.e. operates in the guest physical address space, whereas RIP is a virtual (not even linear) address. The "fix" worked for the problematic KVM selftest because the test identity mapped RIP. Fully revert the hack instead of trying to translate RIP to a GPA, as the non-SEV case is now handled earlier, and KVM cannot access guest page tables to translate RIP. This reverts commit e72436bc. Fixes: e72436bc ("KVM: SVM: avoid infinite loop on NPF from bad address") Reported-by:
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