[Devel] [PATCH RHEL7 COMMIT] ms/KVM: x86/mmu: Remove the defunct update_pte() paging hook
Konstantin Khorenko
khorenko at virtuozzo.com
Tue Apr 19 20:05:53 MSK 2022
The commit is pushed to "branch-rh7-3.10.0-1160.59.1.vz7.186.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1160.59.1.vz7.186.2
------>
commit 2dc5b7b4564c6885d19bd7ff7bf49e15ced6d36a
Author: Sean Christopherson <seanjc at google.com>
Date: Fri Mar 18 22:09:45 2022 +0300
ms/KVM: x86/mmu: Remove the defunct update_pte() paging hook
Remove the update_pte() shadow paging logic, which was obsoleted by
commit 4731d4c7a077 ("KVM: MMU: out of sync shadow core"), but never
removed. As pointed out by Yu, KVM never write protects leaf page
tables for the purposes of shadow paging, and instead marks their
associated shadow page as unsync so that the guest can write PTEs at
will.
The update_pte() path, which predates the unsync logic, optimizes COW
scenarios by refreshing leaf SPTEs when they are written, as opposed to
zapping the SPTE, restarting the guest, and installing the new SPTE on
the subsequent fault. Since KVM no longer write-protects leaf page
tables, update_pte() is unreachable and can be dropped.
Reported-by: Yu Zhang <yu.c.zhang at intel.com>
Signed-off-by: Sean Christopherson <seanjc at google.com>
Message-Id: <20210115004051.4099250-1-seanjc at google.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
https://jira.sw.ru/browse/PSBM-139163
(cherry picked from ms commit c5e2184d1544f9e56140791eff1a351bea2e63b9)
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
---
arch/x86/include/asm/kvm_host.h | 3 ---
arch/x86/kvm/mmu.c | 33 ++-------------------------------
arch/x86/kvm/x86.c | 1 -
3 files changed, 2 insertions(+), 35 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4f72e16c7842..47a6f9737f6b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -362,8 +362,6 @@ struct kvm_mmu {
int (*sync_page)(struct kvm_vcpu *vcpu,
struct kvm_mmu_page *sp);
void (*invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa);
- void (*update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
- u64 *spte, const void *pte);
hpa_t root_hpa;
gpa_t root_cr3;
union kvm_mmu_role mmu_role;
@@ -869,7 +867,6 @@ struct kvm_arch {
struct kvm_vm_stat {
ulong mmu_shadow_zapped;
ulong mmu_pte_write;
- ulong mmu_pte_updated;
ulong mmu_pde_zapped;
ulong mmu_flooded;
ulong mmu_recycled;
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index dc28b530ff51..206b4dd9f6d1 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2071,13 +2071,6 @@ static void nonpaging_invlpg(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root)
{
}
-static void nonpaging_update_pte(struct kvm_vcpu *vcpu,
- struct kvm_mmu_page *sp, u64 *spte,
- const void *pte)
-{
- WARN_ON(1);
-}
-
#define KVM_PAGE_ARRAY_NR 16
struct kvm_mmu_pages {
@@ -4169,7 +4162,6 @@ static void nonpaging_init_context(struct kvm_vcpu *vcpu,
context->gva_to_gpa = nonpaging_gva_to_gpa;
context->sync_page = nonpaging_sync_page;
context->invlpg = nonpaging_invlpg;
- context->update_pte = nonpaging_update_pte;
context->root_level = 0;
context->shadow_root_level = PT32E_ROOT_LEVEL;
context->direct_map = true;
@@ -4722,7 +4714,6 @@ static void paging64_init_context_common(struct kvm_vcpu *vcpu,
context->gva_to_gpa = paging64_gva_to_gpa;
context->sync_page = paging64_sync_page;
context->invlpg = paging64_invlpg;
- context->update_pte = paging64_update_pte;
context->shadow_root_level = level;
context->direct_map = false;
}
@@ -4748,7 +4739,6 @@ static void paging32_init_context(struct kvm_vcpu *vcpu,
context->gva_to_gpa = paging32_gva_to_gpa;
context->sync_page = paging32_sync_page;
context->invlpg = paging32_invlpg;
- context->update_pte = paging32_update_pte;
context->shadow_root_level = PT32E_ROOT_LEVEL;
context->direct_map = false;
}
@@ -4821,7 +4811,6 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
context->page_fault = tdp_page_fault;
context->sync_page = nonpaging_sync_page;
context->invlpg = nonpaging_invlpg;
- context->update_pte = nonpaging_update_pte;
context->shadow_root_level = kvm_x86_ops->get_tdp_level();
context->direct_map = true;
context->set_cr3 = kvm_x86_ops->set_tdp_cr3;
@@ -4951,7 +4940,6 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
context->gva_to_gpa = ept_gva_to_gpa;
context->sync_page = ept_sync_page;
context->invlpg = ept_invlpg;
- context->update_pte = ept_update_pte;
context->root_level = PT64_ROOT_4LEVEL;
context->direct_map = false;
context->mmu_role.as_u64 = new_role.as_u64;
@@ -5088,19 +5076,6 @@ void kvm_mmu_unload(struct kvm_vcpu *vcpu)
}
EXPORT_SYMBOL_GPL(kvm_mmu_unload);
-static void mmu_pte_write_new_pte(struct kvm_vcpu *vcpu,
- struct kvm_mmu_page *sp, u64 *spte,
- const void *new)
-{
- if (sp->role.level != PT_PAGE_TABLE_LEVEL) {
- ++vcpu->kvm->stat.mmu_pde_zapped;
- return;
- }
-
- ++vcpu->kvm->stat.mmu_pte_updated;
- vcpu->arch.mmu->update_pte(vcpu, sp, spte, new);
-}
-
static bool need_remote_flush(u64 old, u64 new)
{
if (!is_shadow_present_pte(old))
@@ -5266,14 +5241,10 @@ static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
local_flush = true;
while (npte--) {
- u32 base_role = vcpu->arch.mmu->mmu_role.base.word;
-
entry = *spte;
mmu_page_zap_pte(vcpu->kvm, sp, spte);
- if (gentry &&
- !((sp->role.word ^ base_role)
- & mmu_base_role_mask.word) && rmap_can_add(vcpu))
- mmu_pte_write_new_pte(vcpu, sp, spte, &gentry);
+ if (gentry && sp->role.level != PG_LEVEL_4K)
+ ++vcpu->kvm->stat.mmu_pde_zapped;
if (need_remote_flush(entry, *spte))
remote_flush = true;
++spte;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c7a6afd8c226..782323403d7f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -190,7 +190,6 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
{ "l1d_flush", VCPU_STAT(l1d_flush) },
{ "mmu_shadow_zapped", VM_STAT(mmu_shadow_zapped) },
{ "mmu_pte_write", VM_STAT(mmu_pte_write) },
- { "mmu_pte_updated", VM_STAT(mmu_pte_updated) },
{ "mmu_pde_zapped", VM_STAT(mmu_pde_zapped) },
{ "mmu_flooded", VM_STAT(mmu_flooded) },
{ "mmu_recycled", VM_STAT(mmu_recycled) },
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