linux

iv/linux

History

Maxim Levitsky 841c2be09f kvm: x86: replace kvm_spec_ctrl_test_value with runtime test on the host

To avoid complex and in some cases incorrect logic in
kvm_spec_ctrl_test_value, just try the guest's given value on the host
processor instead, and if it doesn't #GP, allow the guest to set it.

One such case is when host CPU supports STIBP mitigation
but doesn't support IBRS (as is the case with some Zen2 AMD cpus),
and in this case we were giving guest #GP when it tried to use STIBP

The reason why can can do the host test is that IA32_SPEC_CTRL msr is
passed to the guest, after the guest sets it to a non zero value
for the first time (due to performance reasons),
and as as result of this, it is pointless to emulate #GP condition on
this first access, in a different way than what the host CPU does.

This is based on a patch from Sean Christopherson, who suggested this idea.

Fixes: 6441fa6178f5 ("KVM: x86: avoid incorrect writes to host MSR_IA32_SPEC_CTRL")
Cc: stable@vger.kernel.org
Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20200708115731.180097-1-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2020-07-09 07:08:38 -04:00

capabilities.h

KVM: x86/pmu: Support full width counting

2020-06-01 04:26:09 -04:00

evmcs.c

KVM: eVMCS: check if nesting is enabled

2020-04-23 09:04:56 -04:00

evmcs.h

KVM: nVMX: properly handle errors in nested_vmx_handle_enlightened_vmptrld()

2020-03-16 18:19:30 +01:00

nested.c

KVM: x86: Rename cpuid_update() callback to vcpu_after_set_cpuid()