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KVM: SEV-ES: Delegate LBR virtualization to the processor
As documented in APM[1], LBR Virtualization must be enabled for SEV-ES guests. Although KVM currently enforces LBRV for SEV-ES guests, there are multiple issues with it: o MSR_IA32_DEBUGCTLMSR is still intercepted. Since MSR_IA32_DEBUGCTLMSR interception is used to dynamically toggle LBRV for performance reasons, this can be fatal for SEV-ES guests. For ex SEV-ES guest on Zen3: [guest ~]# wrmsr 0x1d9 0x4 KVM: entry failed, hardware error 0xffffffff EAX=00000004 EBX=00000000 ECX=000001d9 EDX=00000000 Fix this by never intercepting MSR_IA32_DEBUGCTLMSR for SEV-ES guests. No additional save/restore logic is required since MSR_IA32_DEBUGCTLMSR is of swap type A. o KVM will disable LBRV if userspace sets MSR_IA32_DEBUGCTLMSR before the VMSA is encrypted. Fix this by moving LBRV enablement code post VMSA encryption. [1]: AMD64 Architecture Programmer's Manual Pub. 40332, Rev. 4.07 - June 2023, Vol 2, 15.35.2 Enabling SEV-ES. https://bugzilla.kernel.org/attachment.cgi?id=304653 Fixes: 376c6d2 ("KVM: SVM: Provide support for SEV-ES vCPU creation/loading") Co-developed-by: Nikunj A Dadhania <nikunj@amd.com> Signed-off-by: Nikunj A Dadhania <nikunj@amd.com> Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com> Message-ID: <20240531044644.768-4-ravi.bangoria@amd.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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