- 19 Jan, 2022 14 commits
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Sean Christopherson authored
Add a VMX specific test to verify that KVM doesn't explode if userspace attempts KVM_RUN when emulation is required with a pending exception. KVM VMX's emulation support for !unrestricted_guest punts exceptions to userspace instead of attempting to synthesize the exception with all the correct state (and stack switching, etc...). Punting is acceptable as there's never been a request to support injecting exceptions when emulating due to invalid state, but KVM has historically assumed that userspace will do the right thing and either clear the exception or kill the guest. Deliberately do the opposite and attempt to re-enter the guest with a pending exception and emulation required to verify KVM continues to punt the combination to userspace, e.g. doesn't explode, WARN, etc... Signed-off-by:
Sean Christopherson <seanjc@google.com> Message-Id: <20211228232437.1875318-3-seanjc@google.com> Signed-off-by:
Paolo Bonzini <pbonzini@redhat.com>
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Sean Christopherson authored
Reject KVM_RUN if emulation is required (because VMX is running without unrestricted guest) and an exception is pending, as KVM doesn't support emulating exceptions except when emulating real mode via vm86. The vCPU is hosed either way, but letting KVM_RUN proceed triggers a WARN due to the impossible condition. Alternatively, the WARN could be removed, but then userspace and/or KVM bugs would result in the vCPU silently running in a bad state, which isn't very friendly to users. Originally, the bug was hit by syzkaller with a nested guest as that doesn't require kvm_intel.unrestricted_guest=0. That particular flavor is likely fixed by commit cd0e615c ("KVM: nVMX: Synthesize TRIPLE_FAULT for L2 if emulation is required"), but it's trivial to trigger the WARN with a non-nested guest, and userspace can likely force bad state via ioctls() for a nested guest as well. Checking for the impossible condition needs to be deferred until KVM_RUN because KVM can't force specific ordering between ioctls. E.g. clearing exception.pending in KVM_SET_SREGS doesn't prevent userspace from setting it in KVM_SET_VCPU_EVENTS, and disallowing KVM_SET_VCPU_EVENTS with emulation_required would prevent userspace from queuing an exception and then stuffing sregs. Note, if KVM were to try and detect/prevent the condition prior to KVM_RUN, handle_invalid_guest_state() and/or handle_emulation_failure() would need to be modified to clear the pending exception prior to exiting to userspace. ------------[ cut here ]------------ WARNING: CPU: 6 PID: 137812 at arch/x86/kvm/vmx/vmx.c:1623 vmx_queue_exception+0x14f/0x160 [kvm_intel] CPU: 6 PID: 137812 Comm: vmx_invalid_nes Not tainted 5.15.2-7cc36c3e14ae-pop #279 Hardware name: ASUS Q87M-E/Q87M-E, BIOS 1102 03/03/2014 RIP: 0010:vmx_queue_exception+0x14f/0x160 [kvm_intel] Code: <0f> 0b e9 fd fe ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 RSP: 0018:ffffa45c83577d38 EFLAGS: 00010202 RAX: 0000000000000003 RBX: 0000000080000006 RCX: 0000000000000006 RDX: 0000000000000000 RSI: 0000000000010002 RDI: ffff9916af734000 RBP: ffff9916af734000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000006 R13: 0000000000000000 R14: ffff9916af734038 R15: 0000000000000000 FS: 00007f1e1a47c740(0000) GS:ffff99188fb80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f1e1a6a8008 CR3: 000000026f83b005 CR4: 00000000001726e0 Call Trace: kvm_arch_vcpu_ioctl_run+0x13a2/0x1f20 [kvm] kvm_vcpu_ioctl+0x279/0x690 [kvm] __x64_sys_ioctl+0x83/0xb0 do_syscall_64+0x3b/0xc0 entry_SYSCALL_64_after_hwframe+0x44/0xae Reported-by: syzbot+82112403ace4cbd780d8@syzkaller.appspotmail.com Signed-off-by:
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Jim Mattson authored
Verify that the PMU event filter works as expected. Note that the virtual PMU doesn't work as expected on AMD Zen CPUs (an intercepted rdmsr is counted as a retired branch instruction), but the PMU event filter does work. Signed-off-by:
Jim Mattson <jmattson@google.com> Signed-off-by:
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Jim Mattson authored
Extract the x86 model number from CPUID.01H:EAX. Signed-off-by:
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Jim Mattson authored
Move this static inline function to processor.h, so that it can be used in individual tests, as needed. Opportunistically replace the bare 'unsigned' with 'unsigned int.' Signed-off-by:
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Jim Mattson authored
Replace the one ad hoc "AuthenticAMD" CPUID vendor string comparison with a new function, is_amd_cpu(). Signed-off-by:
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Jim Mattson authored
Refactor is_intel_cpu() to make it easier to reuse the bulk of the code for other vendors in the future. Signed-off-by:
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Jim Mattson authored
The PMU event filter may contain up to 300 events. Replace the linear search in reprogram_gp_counter() with a binary search. Signed-off-by:
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Wei Wang authored
vm_xsave_req_perm() is currently defined and used by x86_64 only. Make it compiled into vm_create_with_vcpus() only when on x86_64 machines. Otherwise, it would cause linkage errors, e.g. on s390x. Fixes: 415a3c33 ("kvm: selftests: Add support for KVM_CAP_XSAVE2") Reported-by:
Janis Schoetterl-Glausch <scgl@linux.ibm.com> Signed-off-by:
Wei Wang <wei.w.wang@intel.com> Tested-by:
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Like Xu authored
According to Intel extended feature disable (XFD) spec, the sub-function i (i > 1) of CPUID function 0DH enumerates "details for state component i. ECX[2] enumerates support for XFD support for this state component." If KVM does not report F(XFD) feature (e.g. due to CONFIG_X86_64), then the corresponding XFD support for any state component i should also be removed. Translate this dependency into KVM terms. Fixes: 690a757d ("kvm: x86: Add CPUID support for Intel AMX") Signed-off-by:
Like Xu <likexu@tencent.com> Message-Id: <20220117074531.76925-1-likexu@tencent.com> Signed-off-by:
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David Matlack authored
Rewrite the comment in kvm_mmu_slot_remove_write_access() that explains why it is safe to flush TLBs outside of the MMU lock after write-protecting SPTEs for dirty logging. The current comment is a long run-on sentence that was difficult to understand. In addition it was specific to the shadow MMU (mentioning mmu_spte_update()) when the TDP MMU has to handle this as well. The new comment explains: - Why the TLB flush is necessary at all. - Why it is desirable to do the TLB flush outside of the MMU lock. - Why it is safe to do the TLB flush outside of the MMU lock. No functional change intended. Signed-off-by:
David Matlack <dmatlack@google.com> Message-Id: <20220113233020.3986005-5-dmatlack@google.com> Reviewed-by:
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David Matlack authored
SPTEs are tagged with software-only bits to indicate if it is "MMU-writable" and "Host-writable". These bits are used to determine why KVM has marked an SPTE as read-only. Document these bits and their invariants, and enforce the invariants with new WARNs in spte_can_locklessly_be_made_writable() to ensure they are not accidentally violated in the future. Opportunistically move DEFAULT_SPTE_{MMU,HOST}_WRITABLE next to EPT_SPTE_{MMU,HOST}_WRITABLE since the new documentation applies to both. No functional change intended. Signed-off-by: -
David Matlack authored
When handling the changed_pte notifier and the new PTE is read-only, clear both the Host-writable and MMU-writable bits in the SPTE. This preserves the invariant that MMU-writable is set if-and-only-if Host-writable is set. No functional change intended. Nothing currently relies on the aforementioned invariant and technically the changed_pte notifier is dead code. Signed-off-by:
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David Matlack authored
When the TDP MMU is write-protection GFNs for page table protection (as opposed to for dirty logging, or due to the HVA not being writable), it checks if the SPTE is already write-protected and if so skips modifying the SPTE and the TLB flush. This behavior is incorrect because it fails to check if the SPTE is write-protected for page table protection, i.e. fails to check that MMU-writable is '0'. If the SPTE was write-protected for dirty logging but not page table protection, the SPTE could locklessly be made writable, and vCPUs could still be running with writable mappings cached in their TLB. Fix this by only skipping setting the SPTE if the SPTE is already write-protected *and* MMU-writable is already clear. Technically, checking only MMU-writable would suffice; a SPTE cannot be writable without MMU-writable being set. But check both to be paranoid and because it arguably yields more readable code. Fixes: 46044f72 ("kvm: x86/mmu: Support write protection for nesting in tdp MMU") Cc: stable@vger.kernel.org Signed-off-by:
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- 17 Jan, 2022 6 commits
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Like Xu authored
The new module parameter to control PMU virtualization should apply to Intel as well as AMD, for situations where userspace is not trusted. If the module parameter allows PMU virtualization, there could be a new KVM_CAP or guest CPUID bits whereby userspace can enable/disable PMU virtualization on a per-VM basis. If the module parameter does not allow PMU virtualization, there should be no userspace override, since we have no precedent for authorizing that kind of override. If it's false, other counter-based profiling features (such as LBR including the associated CPUID bits if any) will not be exposed. Change its name from "pmu" to "enable_pmu" as we have temporary variables with the same name in our code like "struct kvm_pmu *pmu". Fixes: b1d66dad ("KVM: x86/svm: Add module param to control PMU virtualization") Suggested-by : Jim Mattson <jmattson@google.com> Signed-off-by:
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Vitaly Kuznetsov authored
KVM forbids KVM_SET_CPUID2 after KVM_RUN was performed on a vCPU unless the supplied CPUID data is equal to what was previously set. Test this. Signed-off-by:
Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20220117150542.2176196-5-vkuznets@redhat.com> Signed-off-by:
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Vitaly Kuznetsov authored
In preparation to reusing the existing 'get_cpuid_test' for testing "KVM_SET_CPUID{,2} after KVM_RUN" rename it to 'cpuid_test' to avoid the confusion. No functional change intended. Signed-off-by: -
Vitaly Kuznetsov authored
Commit feb627e8 ("KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN") forbade changing CPUID altogether but unfortunately this is not fully compatible with existing VMMs. In particular, QEMU reuses vCPU fds for CPU hotplug after unplug and it calls KVM_SET_CPUID2. Instead of full ban, check whether the supplied CPUID data is equal to what was previously set. Reported-by:
Igor Mammedov <imammedo@redhat.com> Fixes: feb627e8 ("KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN") Signed-off-by:
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Vitaly Kuznetsov authored
kvm_update_cpuid_runtime() mangles CPUID data coming from userspace VMM after updating 'vcpu->arch.cpuid_entries', this makes it impossible to compare an update with what was previously supplied. Introduce __kvm_update_cpuid_runtime() version which can be used to tweak the input before it goes to 'vcpu->arch.cpuid_entries' so the upcoming update check can compare tweaked data. No functional change intended. Signed-off-by:
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Like Xu authored
According to CPUID 0x0A.EBX bit vector, the event [7] should be the unrealized event "Topdown Slots" instead of the *kernel* generalized common hardware event "REF_CPU_CYCLES", so we need to skip the cpuid unavaliblity check in the intel_pmc_perf_hw_id() for the last REF_CPU_CYCLES event and update the confusing comment. If the event is marked as unavailable in the Intel guest CPUID 0AH.EBX leaf, we need to avoid any perf_event creation, whether it's a gp or fixed counter. To distinguish whether it is a rejected event or an event that needs to be programmed with PERF_TYPE_RAW type, a new special returned value of "PERF_COUNT_HW_MAX + 1" is introduced. Fixes: 62079d8a ("KVM: PMU: add proper support for fixed counter 2") Signed-off-by:
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- 14 Jan, 2022 20 commits
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Yang Zhong authored
Fix sparse warnings in xstate and remove inline prefix. Fixes: 980fe2fd ("x86/fpu: Extend fpu_xstate_prctl() with guest permissions") Signed-off-by:
Yang Zhong <yang.zhong@intel.com> Reported-by:
kernel test robot <lkp@intel.com> Message-Id: <20220113180825.322333-1-yang.zhong@intel.com> Signed-off-by:
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Yang Zhong authored
This selftest covers two aspects of AMX. The first is triggering #NM exception and checking the MSR XFD_ERR value. The second case is loading tile config and tile data into guest registers and trapping to the host side for a complete save/load of the guest state. TMM0 is also checked against memory data after save/restore. Signed-off-by:
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Yang Zhong authored
Those changes can avoid dereferencing pointer compile issue when amx_test.c reference state->xsave. Move struct kvm_x86_state definition to processor.h. Signed-off-by:
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Paolo Bonzini authored
For AMX support it is recommended to load XCR0 after XFD, so that KVM does not see XFD=0, XCR=1 for a save state that will eventually be disabled (which would lead to premature allocation of the space required for that save state). It is also required to load XSAVE data after XCR0 and XFD, so that KVM can trigger allocation of the extra space required to store AMX state. Adjust vcpu_load_state to obey these new requirements. Signed-off-by:
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Kevin Tian authored
Always intercepting IA32_XFD causes non-negligible overhead when this register is updated frequently in the guest. Disable r/w emulation after intercepting the first WRMSR(IA32_XFD) with a non-zero value. Disable WRMSR emulation implies that IA32_XFD becomes out-of-sync with the software states in fpstate and the per-cpu xfd cache. This leads to two additional changes accordingly: - Call fpu_sync_guest_vmexit_xfd_state() after vm-exit to bring software states back in-sync with the MSR, before handle_exit_irqoff() is called. - Always trap #NM once write interception is disabled for IA32_XFD. The #NM exception is rare if the guest doesn't use dynamic features. Otherwise, there is at most one exception per guest task given a dynamic feature. p.s. We have confirmed that SDM is being revised to say that when setting IA32_XFD[18] the AMX register state is not guaranteed to be preserved. This clarification avoids adding mess for a creative guest which sets IA32_XFD[18]=1 before saving active AMX state to its own storage. Signed-off-by:Kevin Tian <kevin.tian@intel.com> Signed-off-by:
Jing Liu <jing2.liu@intel.com> Signed-off-by:
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Thomas Gleixner authored
KVM can disable the write emulation for the XFD MSR when the vCPU's fpstate is already correctly sized to reduce the overhead. When write emulation is disabled the XFD MSR state after a VMEXIT is unknown and therefore not in sync with the software states in fpstate and the per CPU XFD cache. Provide fpu_sync_guest_vmexit_xfd_state() which has to be invoked after a VMEXIT before enabling interrupts when write emulation is disabled for the XFD MSR. It could be invoked unconditionally even when write emulation is enabled for the price of a pointless MSR read. Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
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Wei Wang authored
When KVM_CAP_XSAVE2 is supported, userspace is expected to allocate buffer for KVM_GET_XSAVE2 and KVM_SET_XSAVE using the size returned by KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2). Signed-off-by:
Guang Zeng <guang.zeng@intel.com> Signed-off-by:
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Guang Zeng authored
With KVM_CAP_XSAVE, userspace uses a hardcoded 4KB buffer to get/set xstate data from/to KVM. This doesn't work when dynamic xfeatures (e.g. AMX) are exposed to the guest as they require a larger buffer size. Introduce a new capability (KVM_CAP_XSAVE2). Userspace VMM gets the required xstate buffer size via KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2). KVM_SET_XSAVE is extended to work with both legacy and new capabilities by doing properly-sized memdup_user() based on the guest fpu container. KVM_GET_XSAVE is kept for backward-compatible reason. Instead, KVM_GET_XSAVE2 is introduced under KVM_CAP_XSAVE2 as the preferred interface for getting xstate buffer (4KB or larger size) from KVM (Link: https://lkml.org/lkml/2021/12/15/510) Also, update the api doc with the new KVM_GET_XSAVE2 ioctl. Signed-off-by:
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Thomas Gleixner authored
Userspace needs to inquire KVM about the buffer size to work with the new KVM_SET_XSAVE and KVM_GET_XSAVE2. Add the size info to guest_fpu for KVM to access. Signed-off-by:
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Jing Liu authored
Extend CPUID emulation to support XFD, AMX_TILE, AMX_INT8 and AMX_BF16. Adding those bits into kvm_cpu_caps finally activates all previous logics in this series. Hide XFD on 32bit host kernels. Otherwise it leads to a weird situation where KVM tells userspace to migrate MSR_IA32_XFD and then rejects attempts to read/write the MSR. Signed-off-by:
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Jing Liu authored
Two XCR0 bits are defined for AMX to support XSAVE mechanism. Bit 17 is for tilecfg and bit 18 is for tiledata. The value of XCR0[17:18] is always either 00b or 11b. Also, SDM recommends that only 64-bit operating systems enable Intel AMX by setting XCR0[18:17]. 32-bit host kernel never sets the tile bits in vcpu->arch.guest_supported_xcr0. Signed-off-by:
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Jing Liu authored
This saves one unnecessary VM-exit in guest #NM handler, given that the MSR is already restored with the guest value before the guest is resumed. Suggested-by:
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Jing Liu authored
Emulate read/write to IA32_XFD_ERR MSR. Only the saved value in the guest_fpu container is touched in the emulation handler. Actual MSR update is handled right before entering the guest (with preemption disabled) Signed-off-by:
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Jing Liu authored
Guest IA32_XFD_ERR is generally modified in two places: - Set by CPU when #NM is triggered; - Cleared by guest in its #NM handler; Intercept #NM for the first case when a nonzero value is written to IA32_XFD. Nonzero indicates that the guest is willing to do dynamic fpstate expansion for certain xfeatures, thus KVM needs to manage and virtualize guest XFD_ERR properly. The vcpu exception bitmap is updated in XFD write emulation according to guest_fpu::xfd. Save the current XFD_ERR value to the guest_fpu container in the #NM VM-exit handler. This must be done with interrupt disabled, otherwise the unsaved MSR value may be clobbered by host activity. The saving operation is conducted conditionally only when guest_fpu:xfd includes a non-zero value. Doing so also avoids misread on a platform which doesn't support XFD but #NM is triggered due to L1 interception. Queueing #NM to the guest is postponed to handle_exception_nmi(). This goes through the nested_vmx check so a virtual vmexit is queued instead when #NM is triggered in L2 but L1 wants to intercept it. Restore the host value (always ZERO outside of the host #NM handler) before enabling interrupt. Restore the guest value from the guest_fpu container right before entering the guest (with interrupt disabled). Suggested-by:
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Jing Liu authored
When XFD causes an instruction to generate #NM, IA32_XFD_ERR contains information about which disabled state components are being accessed. The #NM handler is expected to check this information and then enable the state components by clearing IA32_XFD for the faulting task (if having permission). If the XFD_ERR value generated in guest is consumed/clobbered by the host before the guest itself doing so, it may lead to non-XFD-related #NM treated as XFD #NM in host (due to non-zero value in XFD_ERR), or XFD-related #NM treated as non-XFD #NM in guest (XFD_ERR cleared by the host #NM handler). Introduce a new field in fpu_guest to save the guest xfd_err value. KVM is expected to save guest xfd_err before interrupt is enabled and restore it right before entering the guest (with interrupt disabled). Signed-off-by:
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Jing Liu authored
Intel's eXtended Feature Disable (XFD) feature allows the software to dynamically adjust fpstate buffer size for XSAVE features which have large state. Because guest fpstate has been expanded for all possible dynamic xstates at KVM_SET_CPUID2, emulation of the IA32_XFD MSR is straightforward. For write just call fpu_update_guest_xfd() to update the guest fpu container once all the sanity checks are passed. For read simply return the cached value in the container. Signed-off-by:
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Kevin Tian authored
Guest XFD can be updated either in the emulation path or in the restore path. Provide a wrapper to update guest_fpu::fpstate::xfd. If the guest fpstate is currently in-use, also update the per-cpu xfd cache and the actual MSR. Signed-off-by:
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Jing Liu authored
KVM can request fpstate expansion in two approaches: 1) When intercepting guest updates to XCR0 and XFD MSR; 2) Before vcpu runs (e.g. at KVM_SET_CPUID2); The first option doesn't waste memory for legacy guest if it doesn't support XFD. However doing so introduces more complexity and also imposes an order requirement in the restoring path, i.e. XCR0/XFD must be restored before XSTATE. Given that the agreement is to do the static approach. This is considered a better tradeoff though it does waste 8K memory for legacy guest if its CPUID includes dynamically-enabled xfeatures. Successful fpstate expansion requires userspace VMM to acquire guest xstate permissions before calling KVM_SET_CPUID2. Also take the chance to adjust the indent in kvm_set_cpuid(). Signed-off-by:
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Sean Christopherson authored
Provide a wrapper for expanding the guest fpstate buffer according to requested xfeatures. KVM wants to call this wrapper to manage any dynamic xstate used by the guest. Suggested-by:
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Thomas Gleixner authored
Guest support for dynamically enabled FPU features requires a few modifications to the enablement function which is currently invoked from the #NM handler: 1) Use guest permissions and sizes for the update 2) Update fpu_guest state accordingly 3) Take into account that the enabling can be triggered either from a running guest via XSETBV and MSR_IA32_XFD write emulation or from a guest restore. In the latter case the guests fpstate is not the current tasks active fpstate. Split the function and implement the guest mechanics throughout the callchain. Signed-off-by:
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