Michael Roth cf6d9d2d24 KVM: SEV-ES: Fix svm_get_msr()/svm_set_msr() for KVM_SEV_ES_INIT guests ... With commit 27bd5fdc24 ("KVM: SEV-ES: Prevent MSR access post VMSA encryption"), older VMMs like QEMU 9.0 and older will fail when booting SEV-ES guests with something like the following error: qemu-system-x86_64: error: failed to get MSR 0x174 qemu-system-x86_64: ../qemu.git/target/i386/kvm/kvm.c:3950: kvm_get_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed. This is because older VMMs that might still call svm_get_msr()/svm_set_msr() for SEV-ES guests after guest boot even if those interfaces were essentially just noops because of the vCPU state being encrypted and stored separately in the VMSA. Now those VMMs will get an -EINVAL and generally crash. Newer VMMs that are aware of KVM_SEV_INIT2 however are already aware of the stricter limitations of what vCPU state can be sync'd during guest run-time, so newer QEMU for instance will work both for legacy KVM_SEV_ES_INIT interface as well as KVM_SEV_INIT2. So when using KVM_SEV_INIT2 it's okay to assume userspace can deal with -EINVAL, whereas for legacy KVM_SEV_ES_INIT the kernel might be dealing with either an older VMM and so it needs to assume that returning -EINVAL might break the VMM. Address this by only returning -EINVAL if the guest was started with KVM_SEV_INIT2. Otherwise, just silently return. Cc: Ravi Bangoria <ravi.bangoria@amd.com> Cc: Nikunj A Dadhania <nikunj@amd.com> Reported-by: Srikanth Aithal <sraithal@amd.com> Closes: https://lore.kernel.org/lkml/37usuu4yu4ok7be2hqexhmcyopluuiqj3k266z4gajc2rcj4yo@eujb23qc3zcm/ Fixes: 27bd5fdc24 ("KVM: SEV-ES: Prevent MSR access post VMSA encryption") Signed-off-by: Michael Roth <michael.roth@amd.com> Message-ID: <20240604233510.764949-1-michael.roth@amd.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>		2024-06-21 07:11:29 -04:00
..
avic.c
hyperv.c
hyperv.h
nested.c
pmu.c
sev.c	KVM: SEV-ES: Delegate LBR virtualization to the processor	2024-06-03 13:07:18 -04:00
svm.c	KVM: SEV-ES: Fix svm_get_msr()/svm_set_msr() for KVM_SEV_ES_INIT guests	2024-06-21 07:11:29 -04:00
svm.h	KVM: SEV-ES: Delegate LBR virtualization to the processor	2024-06-03 13:07:18 -04:00
svm_onhyperv.c
svm_onhyperv.h
svm_ops.h
vmenter.S	KVM: SVM: Create a stack frame in __svm_sev_es_vcpu_run()	2024-04-09 10:21:10 -07:00