* [PATCH v2] KVM: x86/xen: Take srcu lock when accessing kvm_memslots()
@ 2021-04-23 8:23 Wanpeng Li
2021-04-23 15:18 ` Sean Christopherson
0 siblings, 1 reply; 2+ messages in thread
From: Wanpeng Li @ 2021-04-23 8:23 UTC (permalink / raw)
To: linux-kernel, kvm
Cc: Paolo Bonzini, Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li,
Jim Mattson, Joerg Roedel
From: Wanpeng Li <wanpengli@tencent.com>
kvm_memslots() will be called by kvm_write_guest_offset_cached() so we should
take the srcu lock. Let's pull the srcu lock operation from kvm_steal_time_set_preempted()
again to fix xen part.
Fixes: 30b5c851af7 (KVM: x86/xen: Add support for vCPU runstate information)
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
arch/x86/kvm/x86.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3bf52ba..c775d24 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4097,7 +4097,6 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
{
struct kvm_host_map map;
struct kvm_steal_time *st;
- int idx;
if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
return;
@@ -4105,15 +4104,9 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
if (vcpu->arch.st.preempted)
return;
- /*
- * Take the srcu lock as memslots will be accessed to check the gfn
- * cache generation against the memslots generation.
- */
- idx = srcu_read_lock(&vcpu->kvm->srcu);
-
if (kvm_map_gfn(vcpu, vcpu->arch.st.msr_val >> PAGE_SHIFT, &map,
&vcpu->arch.st.cache, true))
- goto out;
+ return;
st = map.hva +
offset_in_page(vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS);
@@ -4121,20 +4114,25 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
st->preempted = vcpu->arch.st.preempted = KVM_VCPU_PREEMPTED;
kvm_unmap_gfn(vcpu, &map, &vcpu->arch.st.cache, true, true);
-
-out:
- srcu_read_unlock(&vcpu->kvm->srcu, idx);
}
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
+ int idx;
+
if (vcpu->preempted && !vcpu->arch.guest_state_protected)
vcpu->arch.preempted_in_kernel = !static_call(kvm_x86_get_cpl)(vcpu);
+ /*
+ * Take the srcu lock as memslots will be accessed to check the gfn
+ * cache generation against the memslots generation.
+ */
+ idx = srcu_read_lock(&vcpu->kvm->srcu);
if (kvm_xen_msr_enabled(vcpu->kvm))
kvm_xen_runstate_set_preempted(vcpu);
else
kvm_steal_time_set_preempted(vcpu);
+ srcu_read_unlock(&vcpu->kvm->srcu, idx);
static_call(kvm_x86_vcpu_put)(vcpu);
vcpu->arch.last_host_tsc = rdtsc();
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH v2] KVM: x86/xen: Take srcu lock when accessing kvm_memslots()
2021-04-23 8:23 [PATCH v2] KVM: x86/xen: Take srcu lock when accessing kvm_memslots() Wanpeng Li
@ 2021-04-23 15:18 ` Sean Christopherson
0 siblings, 0 replies; 2+ messages in thread
From: Sean Christopherson @ 2021-04-23 15:18 UTC (permalink / raw)
To: Wanpeng Li
Cc: linux-kernel, kvm, Paolo Bonzini, Vitaly Kuznetsov, Wanpeng Li,
Jim Mattson, Joerg Roedel
On Fri, Apr 23, 2021, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
>
> kvm_memslots() will be called by kvm_write_guest_offset_cached() so we should
> take the srcu lock. Let's pull the srcu lock operation from kvm_steal_time_set_preempted()
> again to fix xen part.
>
> Fixes: 30b5c851af7 (KVM: x86/xen: Add support for vCPU runstate information)
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
> arch/x86/kvm/x86.c | 20 +++++++++-----------
> 1 file changed, 9 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3bf52ba..c775d24 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4097,7 +4097,6 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
> {
> struct kvm_host_map map;
> struct kvm_steal_time *st;
> - int idx;
>
> if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
> return;
> @@ -4105,15 +4104,9 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
> if (vcpu->arch.st.preempted)
> return;
>
> - /*
> - * Take the srcu lock as memslots will be accessed to check the gfn
> - * cache generation against the memslots generation.
> - */
> - idx = srcu_read_lock(&vcpu->kvm->srcu);
> -
> if (kvm_map_gfn(vcpu, vcpu->arch.st.msr_val >> PAGE_SHIFT, &map,
> &vcpu->arch.st.cache, true))
> - goto out;
> + return;
>
> st = map.hva +
> offset_in_page(vcpu->arch.st.msr_val & KVM_STEAL_VALID_BITS);
> @@ -4121,20 +4114,25 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
> st->preempted = vcpu->arch.st.preempted = KVM_VCPU_PREEMPTED;
>
> kvm_unmap_gfn(vcpu, &map, &vcpu->arch.st.cache, true, true);
> -
> -out:
> - srcu_read_unlock(&vcpu->kvm->srcu, idx);
> }
>
> void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> {
> + int idx;
> +
> if (vcpu->preempted && !vcpu->arch.guest_state_protected)
> vcpu->arch.preempted_in_kernel = !static_call(kvm_x86_get_cpl)(vcpu);
>
> + /*
> + * Take the srcu lock as memslots will be accessed to check the gfn
> + * cache generation against the memslots generation.
> + */
> + idx = srcu_read_lock(&vcpu->kvm->srcu);
Might be worth grabbing "kvm" in a local variable? Either way:
Reviewed-by: Sean Christopherson <seanjc@google.com>
> if (kvm_xen_msr_enabled(vcpu->kvm))
> kvm_xen_runstate_set_preempted(vcpu);
> else
> kvm_steal_time_set_preempted(vcpu);
> + srcu_read_unlock(&vcpu->kvm->srcu, idx);
>
> static_call(kvm_x86_vcpu_put)(vcpu);
> vcpu->arch.last_host_tsc = rdtsc();
> --
> 2.7.4
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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