Messages in this thread | | | Subject | Re: [PATCH v6 8/8] kvm: vmx: virtualize split lock detection | From | Xiaoyao Li <> | Date | Thu, 26 Mar 2020 20:43:46 +0800 |
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On 3/26/2020 7:10 PM, Thomas Gleixner wrote: > Xiaoyao Li <xiaoyao.li@intel.com> writes: >> On 3/25/2020 8:40 AM, Thomas Gleixner wrote: >>> Xiaoyao Li <xiaoyao.li@intel.com> writes: >>>> static int handle_exception_nmi(struct kvm_vcpu *vcpu) >>>> { >>>> struct vcpu_vmx *vmx = to_vmx(vcpu); >>>> @@ -4725,12 +4746,13 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu) >>>> case AC_VECTOR: >>>> /* >>>> * Reflect #AC to the guest if it's expecting the #AC, i.e. has >>>> - * legacy alignment check enabled. Pre-check host split lock >>>> - * support to avoid the VMREADs needed to check legacy #AC, >>>> - * i.e. reflect the #AC if the only possible source is legacy >>>> - * alignment checks. >>>> + * legacy alignment check enabled or split lock detect enabled. >>>> + * Pre-check host split lock support to avoid further check of >>>> + * guest, i.e. reflect the #AC if host doesn't enable split lock >>>> + * detection. >>>> */ >>>> if (!split_lock_detect_on() || >>>> + guest_cpu_split_lock_detect_on(vmx) || >>>> guest_cpu_alignment_check_enabled(vcpu)) { >>> >>> If the host has split lock detection disabled then how is the guest >>> supposed to have it enabled in the first place? >>> >> It is || > > Again. If the host has it disabled, then the feature flag is OFF. So > how is the hypervisor exposing it in the first place? >
So what's wrong with above code?
If the host has it disabled, !split_lock_detect_on() is true, it skips following check due to ||
I guess you want something like below?
if (!boot_cpu_has(X86_FEATURE_SPLIT_LOCK)) { inject #AC back to guest } else { if (guest_alignment_check_enabled() || guest_sld_on()) inject #AC back to guest }
BTW, there is an issue in my original patch that guest_sld_on() should be checked at last.
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