- 01 Mar, 2022 24 commits
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Sean Christopherson authored
Disable preemption when loading/putting the AVIC during an APICv refresh. If the vCPU task is preempted and migrated ot a different pCPU, the unprotected avic_vcpu_load() could set the wrong pCPU in the physical ID cache/table. Pull the necessary code out of avic_vcpu_{,un}blocking() and into a new helper to reduce the probability of introducing this exact bug a third time. Fixes: df7e4827 ("KVM: SVM: call avic_vcpu_load/avic_vcpu_put when enabling/disabling AVIC") Cc: stable@vger.kernel.org Reported-by:Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by:
Sean Christopherson <seanjc@google.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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Sean Christopherson authored
Exit to userspace if setup_vmgexit_scratch() fails due to OOM or because copying data from guest (userspace) memory failed/faulted. The OOM scenario is clearcut, it's userspace's decision as to whether it should terminate the guest, free memory, etc... As for -EFAULT, arguably, any guest issue is a violation of the guest's contract with userspace, and thus userspace needs to decide how to proceed. E.g. userspace defines what is RAM vs. MMIO and communicates that directly to the guest, KVM is not involved in deciding what is/isn't RAM nor in communicating that information to the guest. If the scratch GPA doesn't resolve to a memslot, then the guest is not honoring the memory configuration as defined by userspace. And if userspace unmaps an hva for whatever reason, then exiting to userspace with -EFAULT is absolutely the right thing to do. KVM's ABI currently sucks and doesn't provide enough information to act on the -EFAULT, but that will hopefully be remedied in the future as there are multiple use cases, e.g. uffd and virtiofs truncation, that shouldn't require any work in KVM beyond returning -EFAULT with a small amount of metadata. KVM could define its ABI such that failure to access the scratch area is reflected into the guest, i.e. establish a contract with userspace, but that's undesirable as it limits KVM's options in the future, e.g. in the potential uffd case any failure on a uaccess needs to kick out to userspace. KVM does have several cases where it reflects these errors into the guest, e.g. kvm_pv_clock_pairing() and Hyper-V emulation, but KVM would preferably "fix" those instead of propagating the falsehood that any memory failure is the guest's fault. Lastly, returning a boolean as an "error" for that a helper that isn't named accordingly never works out well. Fixes: ad5b3532 ("KVM: SVM: Do not terminate SEV-ES guests on GHCB validation failure") Cc: Alper Gun <alpergun@google.com> Cc: Peter Gonda <pgonda@google.com> Signed-off-by:
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Sean Christopherson authored
WARN and bail if is_unsync_root() is passed a root for which there is no shadow page, i.e. is passed the physical address of one of the special roots, which do not have an associated shadow page. The current usage squeaks by without bug reports because neither kvm_mmu_sync_roots() nor kvm_mmu_sync_prev_roots() calls the helper with pae_root or pml4_root, and 5-level AMD CPUs are not generally available, i.e. no one can coerce KVM into calling is_unsync_root() on pml5_root. Note, this doesn't fix the mess with 5-level nNPT, it just (hopefully) prevents KVM from crashing. Cc: Lai Jiangshan <jiangshanlai@gmail.com> Signed-off-by:
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Sean Christopherson authored
Remove the now unused KVM_REQ_MMU_RELOAD, shift KVM_REQ_VM_DEAD into the unoccupied space, and update vcpu-requests.rst, which was missing an entry for KVM_REQ_VM_DEAD. Switching KVM_REQ_VM_DEAD to entry '1' also fixes the stale comment about bits 4-7 being reserved. Reviewed-by:
Claudio Imbrenda <imbrenda@linux.ibm.com> Signed-off-by:
Ben Gardon <bgardon@google.com> Message-Id: <20220225182248.3812651-7-seanjc@google.com> Signed-off-by:
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Sean Christopherson authored
Add an arch request, KVM_REQ_REFRESH_GUEST_PREFIX, to deal with guest prefix changes instead of piggybacking KVM_REQ_MMU_RELOAD. This will allow for the removal of the generic KVM_REQ_MMU_RELOAD, which isn't actually used by generic KVM. No functional change intended. Reviewed-by:
Janosch Frank <frankja@linux.ibm.com> Signed-off-by:
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Sean Christopherson authored
Zap only obsolete roots when responding to zapping a single root shadow page. Because KVM keeps root_count elevated when stuffing a previous root into its PGD cache, shadowing a 64-bit guest means that zapping any root causes all vCPUs to reload all roots, even if their current root is not affected by the zap. For many kernels, zapping a single root is a frequent operation, e.g. in Linux it happens whenever an mm is dropped, e.g. process exits, etc... Signed-off-by:
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Sean Christopherson authored
Remove the generic kvm_reload_remote_mmus() and open code its functionality into the two x86 callers. x86 is (obviously) the only architecture that uses the hook, and is also the only architecture that uses KVM_REQ_MMU_RELOAD in a way that's consistent with the name. That will change in a future patch, as x86's usage when zapping a single shadow page x86 doesn't actually _need_ to reload all vCPUs' MMUs, only MMUs whose root is being zapped actually need to be reloaded. s390 also uses KVM_REQ_MMU_RELOAD, but for a slightly different purpose. Drop the generic code in anticipation of implementing s390 and x86 arch specific requests, which will allow dropping KVM_REQ_MMU_RELOAD entirely. Opportunistically reword the x86 TDP MMU comment to avoid making references to functions (and requests!) when possible, and to remove the rather ambiguous "this". No functional change intended. Cc: Ben Gardon <bgardon@google.com> Signed-off-by:
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Sean Christopherson authored
Replace a KVM_REQ_MMU_RELOAD request with a direct kvm_mmu_unload() call when the guest's CR4.PCIDE changes. This will allow tweaking the logic of KVM_REQ_MMU_RELOAD to free only obsolete/invalid roots, which is the historical intent of KVM_REQ_MMU_RELOAD. The recent PCIDE behavior is the only user of KVM_REQ_MMU_RELOAD that doesn't mark affected roots as obsolete, needs to unconditionally unload the entire MMU, _and_ affects only the current vCPU. Signed-off-by:
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Hou Wenlong authored
KVM: x86/emulator: Move the unhandled outer privilege level logic of far return into __load_segment_descriptor() Outer-privilege level return is not implemented in emulator, move the unhandled logic into __load_segment_descriptor to make it easier to understand why the checks for RET are incomplete. Suggested-by:
Hou Wenlong <houwenlong.hwl@antgroup.com> Message-Id: <5b7188e6388ac9f4567d14eab32db9adf3e00119.1644292363.git.houwenlong.hwl@antgroup.com> Signed-off-by:
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Hou Wenlong authored
Code segment descriptor can be loaded by jmp/call/ret, iret and int. The privilege checks are different between those instructions above realmode. Although, the emulator has use x86_transfer_type enumerate to differentiate them, but it is not really used in __load_segment_descriptor(). Note, far jump/call to call gate, task gate or task state segment are not implemented in emulator. As for far jump/call to code segment, if DPL > CPL for conforming code or (RPL > CPL or DPL != CPL) for non-conforming code, it should trigger #GP. The current checks are ok. As for far return, if RPL < CPL or DPL > RPL for conforming code or DPL != RPL for non-conforming code, it should trigger #GP. Outer level return is not implemented above virtual-8086 mode in emulator. So it implies that RPL <= CPL, but the current checks wouldn't trigger #GP if RPL < CPL. As for code segment loading in task switch, if DPL > RPL for conforming code or DPL != RPL for non-conforming code, it should trigger #TS. Since segment selector is loaded before segment descriptor when load state from tss, it implies that RPL = CPL, so the current checks are ok. The only problem in current implementation is missing RPL < CPL check for far return. However, change code to follow the manual is better. Reviewed-by:
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Hou Wenlong authored
Per Intel's SDM on the "Instruction Set Reference", when loading segment descriptor, not-present segment check should be after all type and privilege checks. But the emulator checks it first, then #NP is triggered instead of #GP if privilege fails and segment is not present. Put not-present segment check after type and privilege checks in __load_segment_descriptor(). Fixes: 38ba30ba (KVM: x86 emulator: Emulate task switch in emulator.c) Reviewed-by:
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Sean Christopherson authored
The main thing that the selftest verifies is that KVM copies x2APIC's ICR[63:32] to/from ICR2 when userspace accesses the vAPIC page via KVM_{G,S}ET_LAPIC. KVM previously split x2APIC ICR to ICR+ICR2 at the time of write (from the guest), and so KVM must preserve that behavior for backwards compatibility between different versions of KVM. It will also test other invariants, e.g. that KVM clears the BUSY flag on ICR writes, that the reserved bits in ICR2 are dropped on writes from the guest, etc... Signed-off-by: -
Sean Christopherson authored
Hide the lapic's "raw" write helper inside lapic.c to force non-APIC code to go through proper helpers when modification the vAPIC state. Keep the read helper visible to outsiders for now, refactoring KVM to hide it too is possible, it will just take more work to do so. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Emulate the x2APIC ICR as a single 64-bit register, as opposed to forking it across ICR and ICR2 as two 32-bit registers. This mirrors hardware behavior for Intel's upcoming IPI virtualization support, which does not split the access. Previous versions of Intel's SDM and AMD's APM don't explicitly state exactly how ICR is reflected in the vAPIC page for x2APIC, KVM just happened to speculate incorrectly. Handling the upcoming behavior is necessary in order to maintain backwards compatibility with KVM_{G,S}ET_LAPIC, e.g. failure to shuffle the 64-bit ICR to ICR+ICR2 and vice versa would break live migration if IPI virtualization support isn't symmetrical across the source and dest. Cc: Zeng Guang <guang.zeng@intel.com> Cc: Chao Gao <chao.gao@intel.com> Cc: Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by: -
Sean Christopherson authored
Add helpers to handle 64-bit APIC read/writes via MSRs to deduplicate the x2APIC and Hyper-V code needed to service reads/writes to ICR. Future support for IPI virtualization will add yet another path where KVM must handle 64-bit APIC MSR reads/write (to ICR). Opportunistically fix the comment in the write path; ICR2 holds the destination (if there's no shorthand), not the vector. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Make the low level read/write lapic helpers static, any accesses to the local APIC from vendor code or non-APIC code should be routed through proper helpers. No functional change intended. Signed-off-by:
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Sean Christopherson authored
WARN if KVM emulates an IPI without clearing the BUSY flag, failure to do so could hang the guest if it waits for the IPI be sent. Opportunistically use APIC_ICR_BUSY macro instead of open coding the magic number, and add a comment to clarify why kvm_recalculate_apic_map() is unconditionally invoked (it's really, really confusing for IPIs due to the existence of fast paths that don't trigger a potential recalc). Signed-off-by:
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Sean Christopherson authored
Don't bother rewriting the ICR value into the vAPIC page on an AVIC IPI virtualization failure, the access is a trap, i.e. the value has already been written to the vAPIC page. The one caveat is if hardware left the BUSY flag set (which appears to happen somewhat arbitrarily), in which case go through the "nodecode" APIC-write path in order to clear the BUSY flag. Signed-off-by:
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Sean Christopherson authored
Use the common kvm_apic_write_nodecode() to handle AVIC/APIC-write traps instead of open coding the same exact code. This will allow making the low level lapic helpers inaccessible outside of lapic.c code. Opportunistically clean up the params to eliminate a bunch of svm=>vcpu reflection. No functional change intended. Signed-off-by:
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Sean Christopherson authored
Use the "raw" helper to read the vAPIC register after an APIC-write trap VM-Exit. Hardware is responsible for vetting the write, and the caller is responsible for sanitizing the offset. This is a functional change, as it means KVM will consume whatever happens to be in the vAPIC page if the write was dropped by hardware. But, unless userspace deliberately wrote garbage into the vAPIC page via KVM_SET_LAPIC, the value should be zero since it's not writable by the guest. This aligns common x86 with SVM's AVIC logic, i.e. paves the way for using the nodecode path to handle APIC-write traps when AVIC is enabled. Signed-off-by:
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Sean Christopherson authored
Move the vAPIC offset adjustments done in the APIC-write trap path from common x86 to VMX in anticipation of using the nodecode path for SVM's AVIC. The adjustment reflects hardware behavior, i.e. it's technically a property of VMX, no common x86. SVM's AVIC behavior is identical, so it's a bit of a moot point, the goal is purely to make it easier to understand why the adjustment is ok. No functional change intended. Signed-off-by:
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Paolo Bonzini authored
Emulating writes to SELF_IPI with a write to ICR has an unwanted side effect: the value of ICR in vAPIC page gets changed. The lists SELF_IPI as write-only, with no associated MMIO offset, so any write should have no visible side effect in the vAPIC page. Reported-by:
Chao Gao <chao.gao@intel.com> Reviewed-by:
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Zhenzhong Duan authored
In emulation of writing to cr8, one of the lowest four bits in TPR[3:0] is kept. According to Intel SDM 10.8.6.1(baremetal scenario): "APIC.TPR[bits 7:4] = CR8[bits 3:0], APIC.TPR[bits 3:0] = 0"; and SDM 28.3(use TPR shadow): "MOV to CR8. The instruction stores bits 3:0 of its source operand into bits 7:4 of VTPR; the remainder of VTPR (bits 3:0 and bits 31:8) are cleared."; and AMD's APM 16.6.4: "Task Priority Sub-class (TPS)-Bits 3 : 0. The TPS field indicates the current sub-priority to be used when arbitrating lowest-priority messages. This field is written with zero when TPR is written using the architectural CR8 register."; so in KVM emulated scenario, clear TPR[3:0] to make a consistent behavior as in other scenarios. This doesn't impact evaluation and delivery of pending virtual interrupts because processor does not use the processor-priority sub-class to determine which interrupts to delivery and which to inhibit. Sub-class is used by hardware to arbitrate lowest priority interrupts, but KVM just does a round-robin style delivery. Fixes: b93463aa ("KVM: Accelerated apic support") Signed-off-by:
Zhenzhong Duan <zhenzhong.duan@intel.com> Reviewed-by:
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Paolo Bonzini authored
For both CR0 and CR4, disassociate the TLB flush logic from the MMU role logic. Instead of relying on kvm_mmu_reset_context() being a superset of various TLB flushes (which is not necessarily going to be the case in the future), always call it if the role changes but also set the various TLB flush requests according to what is in the manual. Signed-off-by:
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- 25 Feb, 2022 16 commits
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Paolo Bonzini authored
For cleanliness, do not leave a stale GVA in the cache after all the roots are cleared. In practice, kvm_mmu_load will go through kvm_mmu_sync_roots if paging is on, and will not use vcpu_match_mmio_gva at all if paging is off. However, leaving data in the cache might cause bugs in the future. Signed-off-by: -
Paolo Bonzini authored
Since the guest PGD is now loaded after the MMU has been set up completely, the desired role for a cache hit is simply the current mmu_role. There is no need to compute it again, so __kvm_mmu_new_pgd can be folded in kvm_mmu_new_pgd. Reviewed-by:
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Paolo Bonzini authored
Now that __kvm_mmu_new_pgd does not look at the MMU's root_level and shadow_root_level anymore, pull the PGD load after the initialization of the shadow MMUs. Besides being more intuitive, this enables future simplifications and optimizations because it's not necessary anymore to compute the role outside kvm_init_mmu. In particular, kvm_mmu_reset_context was not attempting to use a cached PGD to avoid having to figure out the new role. With this change, it could follow what nested_{vmx,svm}_load_cr3 are doing, and avoid unloading all the cached roots. Reviewed-by: -
Paolo Bonzini authored
Right now, PGD caching avoids placing a PAE root in the cache by using the old value of mmu->root_level and mmu->shadow_root_level; it does not look for a cached PGD if the old root is a PAE one, and then frees it using kvm_mmu_free_roots. Change the logic instead to free the uncacheable root early. This way, __kvm_new_mmu_pgd is able to look up the cache when going from 32-bit to 64-bit (if there is a hit, the invalid root becomes the least recently used). An example of this is nested virtualization with shadow paging, when a 64-bit L1 runs a 32-bit L2. As a side effect (which is actually the reason why this patch was written), PGD caching does not use the old value of mmu->root_level and mmu->shadow_root_level anymore. Reviewed-by:
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Paolo Bonzini authored
These functions only operate on a given MMU, of which there is more than one in a vCPU (we care about two, because the third does not have any roots and is only used to walk guest page tables). They do need a struct kvm in order to lock the mmu_lock, but they do not needed anything else in the struct kvm_vcpu. So, pass the vcpu->kvm directly to them. Signed-off-by: -
Paolo Bonzini authored
Right now, PGD caching requires a complicated dance of first computing the MMU role and passing it to __kvm_mmu_new_pgd(), and then separately calling kvm_init_mmu(). Part of this is due to kvm_mmu_free_roots using mmu->root_level and mmu->shadow_root_level to distinguish whether the page table uses a single root or 4 PAE roots. Because kvm_init_mmu() can overwrite mmu->root_level, kvm_mmu_free_roots() must be called before kvm_init_mmu(). However, even after kvm_init_mmu() there is a way to detect whether the page table may hold PAE roots, as root.hpa isn't backed by a shadow when it points at PAE roots. Using this method results in simpler code, and is one less obstacle in moving all calls to __kvm_mmu_new_pgd() after the MMU has been initialized. Signed-off-by: -
Paolo Bonzini authored
The root_hpa and root_pgd fields form essentially a struct kvm_mmu_root_info. Use the struct to have more consistency between mmu->root and mmu->prev_roots. The patch is entirely search and replace except for cached_root_available, which does not need a temporary struct kvm_mmu_root_info anymore. Reviewed-by:
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Paolo Bonzini authored
WARN and bail if KVM attempts to free a root that isn't backed by a shadow page. KVM allocates a bare page for "special" roots, e.g. when using PAE paging or shadowing 2/3/4-level page tables with 4/5-level, and so root_hpa will be valid but won't be backed by a shadow page. It's all too easy to blindly call mmu_free_root_page() on root_hpa, be nice and WARN instead of crashing KVM and possibly the kernel. Reviewed-by:
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Paolo Bonzini authored
Enabling async page faults is nonsensical if paging is disabled, but it is allowed because CR0.PG=0 does not clear the async page fault MSR. Just ignore them and only use the artificial halt state, similar to what happens in guest mode if async #PF vmexits are disabled. Given the increasingly complex logic, and the nicer code if the new "if" is placed last, opportunistically change the "||" into a chain of "if (...) return false" statements. Reviewed-by:
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Paolo Bonzini authored
While the guest runs, EFER.LME cannot change unless CR0.PG is clear, and therefore EFER.NX is the only bit that can affect the MMU role. However, set_efer accepts a host-initiated change to EFER.LME even with CR0.PG=1. In that case, the MMU has to be reset. Fixes: 11988499 ("KVM: x86: Skip EFER vs. guest CPUID checks for host-initiated writes") Cc: stable@vger.kernel.org Reviewed-by:
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David Dunn authored
On a VM with PMU disabled via KVM_CAP_PMU_CONFIG, the PMU should not be usable by the guest. Signed-off-by:
David Dunn <daviddunn@google.com> Message-Id: <20220223225743.2703915-4-daviddunn@google.com> Signed-off-by:
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David Dunn authored
Carve out portion of vm_create_default so that selftests can modify a "default" VM prior to creating vcpus. Signed-off-by:
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David Dunn authored
Add a new capability, KVM_CAP_PMU_CAPABILITY, that takes a bitmask of settings/features to allow userspace to configure PMU virtualization on a per-VM basis. For now, support a single flag, KVM_PMU_CAP_DISABLE, to allow disabling PMU virtualization for a VM even when KVM is configured with enable_pmu=true a module level. To keep KVM simple, disallow changing VM's PMU configuration after vCPUs have been created. Signed-off-by:
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Sean Christopherson authored
Cast kvm_x86_ops.func to 'void *' when updating KVM static calls that are conditionally patched to __static_call_return0(). clang complains about using mismatching pointers in the ternary operator, which breaks the build when compiling with CONFIG_KVM_WERROR=y. >> arch/x86/include/asm/kvm-x86-ops.h:82:1: warning: pointer type mismatch ('bool (*)(struct kvm_vcpu *)' and 'void *') [-Wpointer-type-mismatch] Fixes: 5be2226f ("KVM: x86: allow defining return-0 static calls") Reported-by:Like Xu <like.xu.linux@gmail.com> Reported-by:
kernel test robot <lkp@intel.com> Signed-off-by:
Nathan Chancellor <nathan@kernel.org> Tested-by:
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Vipin Sharma authored
VM worker kthreads can linger in the VM process's cgroup for sometime after KVM terminates the VM process. KVM terminates the worker kthreads by calling kthread_stop() which waits on the 'exited' completion, triggered by exit_mm(), via mm_release(), in do_exit() during the kthread's exit. However, these kthreads are removed from the cgroup using the cgroup_exit() which happens after the exit_mm(). Therefore, A VM process can terminate in between the exit_mm() and cgroup_exit() calls, leaving only worker kthreads in the cgroup. Moving worker kthreads back to the original cgroup (kthreadd_task's cgroup) makes sure that the cgroup is empty as soon as the main VM process is terminated. Signed-off-by:
Vipin Sharma <vipinsh@google.com> Suggested-by:
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Peng Hao authored
From: Peng Hao <flyingpeng@tencent.com> Remove a redundant 'cpu' declaration from inside an if-statement that that shadows an identical declaration at function scope. Both variables are used as scratch variables in for_each_*_cpu() loops, thus there's no harm in sharing a variable. Reviewed-by:
Peng Hao <flyingpeng@tencent.com> Message-Id: <20220222103954.70062-1-flyingpeng@tencent.com> Signed-off-by:
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