2021-06-09 17:11:35

by Wanpeng Li

Subject: [PATCH v3] KVM: LAPIC: Keep stored TMCCT register value 0 after KVM_SET_LAPIC

From: Wanpeng Li <[email protected]>

KVM_GET_LAPIC stores the current value of TMCCT and KVM_SET_LAPIC's memcpy
stores it in vcpu->arch.apic->regs, KVM_SET_LAPIC could store zero in
vcpu->arch.apic->regs after it uses it, and then the stored value would
always be zero. In addition, the TMCCT is always computed on-demand and
never directly readable.

Suggested-by: Paolo Bonzini <[email protected]>
Signed-off-by: Wanpeng Li <[email protected]>
---
arch/x86/kvm/lapic.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 6d72d8f43310..9bd29b3ca790 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2628,6 +2628,7 @@ int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s)
apic_manage_nmi_watchdog(apic, kvm_lapic_get_reg(apic, APIC_LVT0));
update_divide_count(apic);
__start_apic_timer(apic, APIC_TMCCT);
+ kvm_lapic_set_reg(apic, APIC_TMCCT, 0);
kvm_apic_update_apicv(vcpu);
apic->highest_isr_cache = -1;
if (vcpu->arch.apicv_active) {
--
2.25.1

2021-06-17 04:34:08

by Wanpeng Li

Subject: Re: [PATCH v3] KVM: LAPIC: Keep stored TMCCT register value 0 after KVM_SET_LAPIC

kindly ping, :)
On Wed, 9 Jun 2021 at 15:17, Wanpeng Li <[email protected]> wrote:
>
> From: Wanpeng Li <[email protected]>
>
> KVM_GET_LAPIC stores the current value of TMCCT and KVM_SET_LAPIC's memcpy
> stores it in vcpu->arch.apic->regs, KVM_SET_LAPIC could store zero in
> vcpu->arch.apic->regs after it uses it, and then the stored value would
> always be zero. In addition, the TMCCT is always computed on-demand and
> never directly readable.
>
> Suggested-by: Paolo Bonzini <[email protected]>
> Signed-off-by: Wanpeng Li <[email protected]>
> ---
> arch/x86/kvm/lapic.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 6d72d8f43310..9bd29b3ca790 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -2628,6 +2628,7 @@ int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s)
> apic_manage_nmi_watchdog(apic, kvm_lapic_get_reg(apic, APIC_LVT0));
> update_divide_count(apic);
> __start_apic_timer(apic, APIC_TMCCT);
> + kvm_lapic_set_reg(apic, APIC_TMCCT, 0);
> kvm_apic_update_apicv(vcpu);
> apic->highest_isr_cache = -1;
> if (vcpu->arch.apicv_active) {
> --
> 2.25.1
>

2021-06-18 00:05:42

by Paolo Bonzini

Subject: Re: [PATCH v3] KVM: LAPIC: Keep stored TMCCT register value 0 after KVM_SET_LAPIC

On 09/06/21 09:16, Wanpeng Li wrote:
> From: Wanpeng Li <[email protected]>
>
> KVM_GET_LAPIC stores the current value of TMCCT and KVM_SET_LAPIC's memcpy
> stores it in vcpu->arch.apic->regs, KVM_SET_LAPIC could store zero in
> vcpu->arch.apic->regs after it uses it, and then the stored value would
> always be zero. In addition, the TMCCT is always computed on-demand and
> never directly readable.
>
> Suggested-by: Paolo Bonzini <[email protected]>
> Signed-off-by: Wanpeng Li <[email protected]>
> ---
> arch/x86/kvm/lapic.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 6d72d8f43310..9bd29b3ca790 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -2628,6 +2628,7 @@ int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s)
> apic_manage_nmi_watchdog(apic, kvm_lapic_get_reg(apic, APIC_LVT0));
> update_divide_count(apic);
> __start_apic_timer(apic, APIC_TMCCT);
> + kvm_lapic_set_reg(apic, APIC_TMCCT, 0);
> kvm_apic_update_apicv(vcpu);
> apic->highest_isr_cache = -1;
> if (vcpu->arch.apicv_active) {
>

Queued, thanks.

Paolo