KVM: x86: Reject userspace attempts to access PERF_CAPABILITIES w/o PDCM

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Reject userspace accesses to PERF_CAPABILITIES if PDCM isn't set in guest
CPUID, i.e. if the vCPU doesn't actually have PERF_CAPABILITIES.  But!  Do
so via KVM_MSR_RET_UNSUPPORTED, so that reads get '0' and writes of '0'
are ignored if KVM advertised support PERF_CAPABILITIES.

KVM's ABI is that userspace must set guest CPUID prior to setting MSRs,
and that setting MSRs that aren't supposed exist is disallowed (modulo the
'0' exemption).

Link: https://lore.kernel.org/r/20240802185511.305849-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

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This commit is contained in:

Sean Christopherson 2024-08-02 11:55:06 -07:00

parent dcb988cdac

commit d75cac366f

1 changed files with 6 additions and 5 deletions

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arch/x86/kvm/x86.c

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