2023-01-05 11:17:21

by Lai Jiangshan

Subject: [PATCH] kvm: x86/mmu: Don't clear write flooding for direct SP

From: Lai Jiangshan <[email protected]>

Although there is no harm, but there is no point to clear write
flooding for direct SP.

Signed-off-by: Lai Jiangshan <[email protected]>
---
arch/x86/kvm/mmu/paging_tmpl.h | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 79da423ee4cb..11f17efbec97 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -649,12 +649,12 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
if (WARN_ON(!VALID_PAGE(vcpu->arch.mmu->root.hpa)))
goto out_gpte_changed;

- for (shadow_walk_init(&it, vcpu, fault->addr);
- shadow_walk_okay(&it) && it.level > gw->level;
- shadow_walk_next(&it)) {
+ for_each_shadow_entry(vcpu, fault->addr, it) {
gfn_t table_gfn;

clear_sp_write_flooding_count(it.sptep);
+ if (it.level == gw->level)
+ break;

table_gfn = gw->table_gfn[it.level - 2];
access = gw->pt_access[it.level - 2];
@@ -706,8 +706,6 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
trace_kvm_mmu_spte_requested(fault);

for (; shadow_walk_okay(&it); shadow_walk_next(&it)) {
- clear_sp_write_flooding_count(it.sptep);
-
/*
* We cannot overwrite existing page tables with an NX
* large page, as the leaf could be executable.
--
2.19.1.6.gb485710b

2023-01-19 21:03:22

by Sean Christopherson

Subject: Re: [PATCH] kvm: x86/mmu: Don't clear write flooding for direct SP

On Thu, 05 Jan 2023 18:03:10 +0800, Lai Jiangshan wrote:
> Although there is no harm, but there is no point to clear write
> flooding for direct SP.
>
>

Applied to kvm-x86 mmu, thanks!

[1/1] kvm: x86/mmu: Don't clear write flooding for direct SP
https://github.com/kvm-x86/linux/commit/5ee0c3718540

--
https://github.com/kvm-x86/linux/tree/next
https://github.com/kvm-x86/linux/tree/fixes