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KVM: VMX: Update PT MSR intercepts during filter change iff PT in host+guest

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Update the Processor Trace (PT) MSR intercepts during a filter change if
and only if PT may be exposed to the guest, i.e. only if KVM is operating
in the so called "host+guest" mode where PT can be used simultaneously by
both the host and guest.  If PT is in system mode, the host is the sole
owner of PT and the MSRs should never be passed through to the guest.

Luckily the missed check only results in unnecessary work, as select RTIT
MSRs are passed through only when RTIT tracing is enabled "in" the guest,
and tracing can't be enabled in the guest when KVM is in system mode
(writes to guest.MSR_IA32_RTIT_CTL are disallowed).

Cc: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20220712015838.1253995-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2022-07-12 01:58:38 +00:00
parent 3d5f8d0378
commit b184b35d06
1 changed files with 3 additions and 1 deletions
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4
arch/x86/kvm/vmx/vmx.c
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@@ -4004,7 +4004,9 @@ static void vmx_msr_filter_changed(struct kvm_vcpu *vcpu)
vmx_disable_intercept_for_msr(vcpu, msr, MSR_TYPE_W);
}
pt_update_intercept_for_msr(vcpu);
/* PT MSRs can be passed through iff PT is exposed to the guest. */
if (vmx_pt_mode_is_host_guest())
pt_update_intercept_for_msr(vcpu);
}
static inline void kvm_vcpu_trigger_posted_interrupt(struct kvm_vcpu *vcpu,