* [PATCH] KVM: X86: Avoid to handle first-time write when updating the pv stuffs each time
@ 2017-11-13 6:47 Wanpeng Li
2017-11-13 15:00 ` Paolo Bonzini
0 siblings, 1 reply; 2+ messages in thread
From: Wanpeng Li @ 2017-11-13 6:47 UTC (permalink / raw)
To: linux-kernel, kvm
Cc: Paolo Bonzini, Radim Krčmář, Wanpeng Li, Liran Alon
From: Wanpeng Li <wanpeng.li@hotmail.com>
There is a logic to handle first-time write when updating the
pvclock/wall clock/steal time shared memory pages each time,
actually we should do this logic during pv stuffs setup if we
suspect the version-field can't be guranteed to be initialized
to an even number by the guest. This patch fixes it by handling
the first-time write of pvclock/steal time during setup since
the update is frequent, and keeping the wall clock since it is
rare updating.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
arch/x86/kvm/x86.c | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4552427..19311e0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1833,9 +1833,6 @@ static void kvm_setup_pvclock_page(struct kvm_vcpu *v)
*/
BUILD_BUG_ON(offsetof(struct pvclock_vcpu_time_info, version) != 0);
- if (guest_hv_clock.version & 1)
- ++guest_hv_clock.version; /* first time write, random junk */
-
vcpu->hv_clock.version = guest_hv_clock.version + 1;
kvm_write_guest_cached(v->kvm, &vcpu->pv_time,
&vcpu->hv_clock,
@@ -2126,9 +2123,6 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
vcpu->arch.st.steal.preempted = 0;
- if (vcpu->arch.st.steal.version & 1)
- vcpu->arch.st.steal.version += 1; /* first time write, random junk */
-
vcpu->arch.st.steal.version += 1;
kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
@@ -2256,8 +2250,19 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
&vcpu->arch.pv_time, data & ~1ULL,
sizeof(struct pvclock_vcpu_time_info)))
vcpu->arch.pv_time_enabled = false;
- else
+ else {
+ struct pvclock_vcpu_time_info guest_hv_clock;
+
vcpu->arch.pv_time_enabled = true;
+ if (unlikely(kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.pv_time,
+ &guest_hv_clock, sizeof(guest_hv_clock))))
+ break;
+ if (guest_hv_clock.version & 1)
+ ++guest_hv_clock.version; /* first time write, random junk */
+ kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.pv_time,
+ &vcpu->arch.hv_clock,
+ sizeof(vcpu->arch.hv_clock.version));
+ }
break;
}
@@ -2283,6 +2288,16 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if (!(data & KVM_MSR_ENABLED))
break;
+ if (unlikely(kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
+ &vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
+ break;
+
+ if (vcpu->arch.st.steal.version & 1)
+ vcpu->arch.st.steal.version += 1; /* first time write, random junk */
+
+ kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
+ &vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
+
kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
break;
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] KVM: X86: Avoid to handle first-time write when updating the pv stuffs each time
2017-11-13 6:47 [PATCH] KVM: X86: Avoid to handle first-time write when updating the pv stuffs each time Wanpeng Li
@ 2017-11-13 15:00 ` Paolo Bonzini
0 siblings, 0 replies; 2+ messages in thread
From: Paolo Bonzini @ 2017-11-13 15:00 UTC (permalink / raw)
To: Wanpeng Li, linux-kernel, kvm
Cc: Radim Krčmář, Wanpeng Li, Liran Alon
On 13/11/2017 07:47, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng.li@hotmail.com>
>
> There is a logic to handle first-time write when updating the
> pvclock/wall clock/steal time shared memory pages each time,
> actually we should do this logic during pv stuffs setup if we
> suspect the version-field can't be guranteed to be initialized
> to an even number by the guest. This patch fixes it by handling
> the first-time write of pvclock/steal time during setup since
> the update is frequent, and keeping the wall clock since it is
> rare updating.
The cost is almost zero, and the code is smaller without this patch, so
I think it's a little better to leave things as is.
Paolo
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Liran Alon <liran.alon@oracle.com>
> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
> ---
> arch/x86/kvm/x86.c | 29 ++++++++++++++++++++++-------
> 1 file changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4552427..19311e0 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1833,9 +1833,6 @@ static void kvm_setup_pvclock_page(struct kvm_vcpu *v)
> */
> BUILD_BUG_ON(offsetof(struct pvclock_vcpu_time_info, version) != 0);
>
> - if (guest_hv_clock.version & 1)
> - ++guest_hv_clock.version; /* first time write, random junk */
> -
> vcpu->hv_clock.version = guest_hv_clock.version + 1;
> kvm_write_guest_cached(v->kvm, &vcpu->pv_time,
> &vcpu->hv_clock,
> @@ -2126,9 +2123,6 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
>
> vcpu->arch.st.steal.preempted = 0;
>
> - if (vcpu->arch.st.steal.version & 1)
> - vcpu->arch.st.steal.version += 1; /* first time write, random junk */
> -
> vcpu->arch.st.steal.version += 1;
>
> kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
> @@ -2256,8 +2250,19 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> &vcpu->arch.pv_time, data & ~1ULL,
> sizeof(struct pvclock_vcpu_time_info)))
> vcpu->arch.pv_time_enabled = false;
> - else
> + else {
> + struct pvclock_vcpu_time_info guest_hv_clock;
> +
> vcpu->arch.pv_time_enabled = true;
> + if (unlikely(kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.pv_time,
> + &guest_hv_clock, sizeof(guest_hv_clock))))
> + break;
> + if (guest_hv_clock.version & 1)
> + ++guest_hv_clock.version; /* first time write, random junk */
> + kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.pv_time,
> + &vcpu->arch.hv_clock,
> + sizeof(vcpu->arch.hv_clock.version));
> + }
>
> break;
> }
> @@ -2283,6 +2288,16 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> if (!(data & KVM_MSR_ENABLED))
> break;
>
> + if (unlikely(kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
> + &vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
> + break;
> +
> + if (vcpu->arch.st.steal.version & 1)
> + vcpu->arch.st.steal.version += 1; /* first time write, random junk */
> +
> + kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
> + &vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
> +
> kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
>
> break;
>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2017-11-13 15:00 UTC | newest]
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2017-11-13 6:47 [PATCH] KVM: X86: Avoid to handle first-time write when updating the pv stuffs each time Wanpeng Li
2017-11-13 15:00 ` Paolo Bonzini
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