2020-06-05 21:42:06

by Sean Christopherson

Subject: [PATCH 06/21] KVM: x86/mmu: Move fast_page_fault() call above mmu_topup_memory_caches()

Avoid refilling the memory caches and potentially slow reclaim/swap when
handling a fast page fault, which does not need to allocate any new
objects.

Signed-off-by: Sean Christopherson <[email protected]>
---
arch/x86/kvm/mmu/mmu.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 5e773564ab20..4b4c3234d623 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4095,6 +4095,9 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
if (page_fault_handle_page_track(vcpu, error_code, gfn))
return RET_PF_EMULATE;

+ if (fast_page_fault(vcpu, gpa, error_code))
+ return RET_PF_RETRY;
+
r = mmu_topup_memory_caches(vcpu);
if (r)
return r;
@@ -4102,9 +4105,6 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
if (lpage_disallowed)
max_level = PG_LEVEL_4K;

- if (fast_page_fault(vcpu, gpa, error_code))
- return RET_PF_RETRY;
-
mmu_seq = vcpu->kvm->mmu_notifier_seq;
smp_rmb();

--
2.26.0

2020-06-09 23:06:44

by Ben Gardon

Subject: Re: [PATCH 06/21] KVM: x86/mmu: Move fast_page_fault() call above mmu_topup_memory_caches()

On Fri, Jun 5, 2020 at 2:39 PM Sean Christopherson
<[email protected]> wrote:
>
> Avoid refilling the memory caches and potentially slow reclaim/swap when
> handling a fast page fault, which does not need to allocate any new
> objects.
>
> Signed-off-by: Sean Christopherson <[email protected]>
Reviewed-by: Ben Gardon <[email protected]>
> ---
> arch/x86/kvm/mmu/mmu.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 5e773564ab20..4b4c3234d623 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4095,6 +4095,9 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
> if (page_fault_handle_page_track(vcpu, error_code, gfn))
> return RET_PF_EMULATE;
>
> + if (fast_page_fault(vcpu, gpa, error_code))
> + return RET_PF_RETRY;
> +
> r = mmu_topup_memory_caches(vcpu);
> if (r)
> return r;
> @@ -4102,9 +4105,6 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
> if (lpage_disallowed)
> max_level = PG_LEVEL_4K;
>
> - if (fast_page_fault(vcpu, gpa, error_code))
> - return RET_PF_RETRY;
> -
> mmu_seq = vcpu->kvm->mmu_notifier_seq;
> smp_rmb();
>
> --
> 2.26.0
>