Messages in this thread | | | Date | Thu, 18 Nov 2021 17:05:22 +0100 | Subject | Re: [PATCH 05/15] KVM: VMX: Add document to state that write to uret msr should always be intercepted | From | Paolo Bonzini <> |
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On 11/18/21 12:08, Lai Jiangshan wrote: > From: Lai Jiangshan <laijs@linux.alibaba.com> > > And adds a corresponding sanity check code. > > Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> > --- > arch/x86/kvm/vmx/vmx.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index e8a41fdc3c4d..cd081219b668 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -3703,13 +3703,21 @@ void vmx_disable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type) > if (!cpu_has_vmx_msr_bitmap()) > return; > > + /* > + * Write to uret msr should always be intercepted due to the mechanism > + * must know the current value. Santity check to avoid any inadvertent > + * mistake in coding. > + */ > + if (WARN_ON_ONCE(vmx_find_uret_msr(vmx, msr) && (type & MSR_TYPE_W))) > + return; > +
I'm not sure about this one, it's relatively expensive to call vmx_find_uret_msr.
User-return MSRs and disable-intercept MSRs are almost the opposite: uret is for MSRs that the host (not even the processor) never uses, disable-intercept is for MSRs that the guest reads/writes often. As such it seems almost impossible that they overlap.
Paolo
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