Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [PATCH] KVM: x86: VMX: hyper-v: Enlightened MSR-Bitmap support | Date | Fri, 13 Apr 2018 16:23:37 +0200 |
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Paolo Bonzini <pbonzini@redhat.com> writes:
> On 12/04/2018 17:25, Vitaly Kuznetsov wrote: >> @@ -5335,6 +5353,9 @@ static void __always_inline vmx_disable_intercept_for_msr(unsigned long *msr_bit >> if (!cpu_has_vmx_msr_bitmap()) >> return; >> >> + if (static_branch_unlikely(&enable_emsr_bitmap)) >> + evmcs_touch_msr_bitmap(); >> + >> /* >> * See Intel PRM Vol. 3, 20.6.9 (MSR-Bitmap Address). Early manuals >> * have the write-low and read-high bitmap offsets the wrong way round. >> @@ -5370,6 +5391,9 @@ static void __always_inline vmx_enable_intercept_for_msr(unsigned long *msr_bitm >> if (!cpu_has_vmx_msr_bitmap()) >> return; >> >> + if (static_branch_unlikely(&enable_emsr_bitmap)) >> + evmcs_touch_msr_bitmap(); > > I'm not sure about the "unlikely". Can you just check current_evmcs > instead (dropping the static key completely)?
current_evmcs is just a cast:
(struct hv_enlightened_vmcs *)this_cpu_read(current_vmcs)
so it is always not NULL here :-) We need to check enable_evmcs static key first. Getting rid of the newly added enable_emsr_bitmap is, of course, possible.
(Actually, we only call vmx_{dis,en}able_intercept_for_msr in the very beginning of vCPUs life so this is not a hotpath and likeliness doesn't really matter).
Will do v2 without the static key, thanks!
> > The function, also, is small enough that inlining should be beneficial. > > Paolo
-- Vitaly
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