lkml.org 
[lkml]   [2017]   [Nov]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH RESEND 3/3] KVM: Add flush_on_enter before guest enter
2017-11-09 18:54 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
> On 09/11/2017 03:02, Wanpeng Li wrote:
>> From: Wanpeng Li <wanpeng.li@hotmail.com>
>>
>> PV-Flush guest would indicate to flush on enter, flush the TLB before
>> entering and exiting the guest.
>>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Radim Krčmář <rkrcmar@redhat.com>
>> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
>> ---
>> arch/x86/kvm/x86.c | 12 ++++++++++--
>> 1 file changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 1ea28a2..f295360 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -2116,7 +2116,13 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
>> &vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
>> return;
>>
>> - vcpu->arch.st.steal.preempted = KVM_VCPU_NOT_PREEMPTED;
>> + if (xchg(&vcpu->arch.st.steal.preempted, KVM_VCPU_NOT_PREEMPTED) ==
>> + (KVM_VCPU_SHOULD_FLUSH | KVM_VCPU_PREEMPTED))
>> + /*
>> + * Do TLB_FLUSH before entering the guest, its passed
>> + * the stage of request checking
>> + */
>> + kvm_x86_ops->tlb_flush(vcpu);
>>
>> if (vcpu->arch.st.steal.version & 1)
>> vcpu->arch.st.steal.version += 1; /* first time write, random junk */
>> @@ -2887,7 +2893,9 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
>> if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
>> return;
>>
>> - vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED;
>> + if (xchg(&vcpu->arch.st.steal.preempted, KVM_VCPU_PREEMPTED) ==
>> + KVM_VCPU_SHOULD_FLUSH)
>> + kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
>
> This is not necessary. Instead, you can just OR the KVM_VCPU_PREEMPTED
> bit; record_steal_time will pick up the request and do the TLB flush later.
>
> Also, I think this is a case where you should prefer INVVPID to INVEP.
> That's because "execution of the INVEPT instruction invalidates
> guest-physical mappings and combined mappings" while "execution of the
> INVVPID instruction invalidates linear mappings and combined mappings".
> In this case, invalidating guest-physical mapping is unnecessary.
>
> So you could add a new bool argument to kvm_x86_ops->tlb_flush. In
> vmx.c, __vmx_flush_tlb can do invept if "enable_ept && (invalidate_gpa
> || !enable_vpid)".

Agreed.

Regards,
Wanpeng Li

\
 
 \ /
  Last update: 2017-11-09 13:31    [W:0.045 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site