[PATCH 21/28] KVM: x86/mmu: propagate access mask from root pages down

Paolo Bonzini
2026-04-30T15:08:12Z

Until now, all SPTEs have had all kinds of access allowed; however,
for GMET to be enabled all the pages have to have ACC_USER_MASK
disabled. By marking them as supervisor pages, the processor
allows execution from either user or supervisor mode (unlike
for normal paging, NPT ignores the U bit for reads and writes).
That will mean that the root page's role has ACC_USER_MASK
cleared and that has to be propagated down through the kvm_mmu_page
tree.

Do that, and pass the required access to the
kvm_mmu_spte_requested tracepoint since it's not ACC_ALL
anymore.

Tested-by: David Riley <d.riley@proxmox.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/mmu/mmu.c | 9 +++++----
arch/x86/kvm/mmu/mmutrace.h | 10 ++++++----
arch/x86/kvm/mmu/paging_tmpl.h | 2 +-
arch/x86/kvm/mmu/tdp_mmu.c | 6 +++---
4 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 27776d0b2ad9..5836ff595e32 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3446,12 +3446,13 @@ static int direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
struct kvm_shadow_walk_iterator it;
struct kvm_mmu_page *sp;
- int ret;
+ int ret, access;
gfn_t base_gfn = fault->gfn;

kvm_mmu_hugepage_adjust(vcpu, fault);

- trace_kvm_mmu_spte_requested(fault);
+ access = vcpu->arch.mmu->root_role.access;
+ trace_kvm_mmu_spte_requested(fault, access);
for_each_shadow_entry(vcpu, fault->addr, it) {
/*
* We cannot overwrite existing page tables with an NX
@@ -3464,7 +3465,7 @@ static int direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
if (it.level == fault->goal_level)
break;

- sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn, true, ACC_ALL);
+ sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn, true, access);
if (sp == ERR_PTR(-EEXIST))
continue;

@@ -3477,7 +3478,7 @@ static int direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
if (WARN_ON_ONCE(it.level != fault->goal_level))
return -EFAULT;

- ret = mmu_set_spte(vcpu, fault->slot, it.sptep, ACC_ALL,
+ ret = mmu_set_spte(vcpu, fault->slot, it.sptep, access,
base_gfn, fault->pfn, fault);
if (ret == RET_PF_SPURIOUS)
return ret;
diff --git a/arch/x86/kvm/mmu/mmutrace.h b/arch/x86/kvm/mmu/mmutrace.h
index 3429c1413f42..fa01719baf8d 100644
--- a/arch/x86/kvm/mmu/mmutrace.h
+++ b/arch/x86/kvm/mmu/mmutrace.h
@@ -373,23 +373,25 @@ TRACE_EVENT(

TRACE_EVENT(
kvm_mmu_spte_requested,
- TP_PROTO(struct kvm_page_fault *fault),
- TP_ARGS(fault),
+ TP_PROTO(struct kvm_page_fault *fault, u8 access),
+ TP_ARGS(fault, access),

TP_STRUCT__entry(
__field(u64, gfn)
__field(u64, pfn)
__field(u8, level)
+ __field(u8, access)
),

TP_fast_assign(
__entry->gfn = fault->gfn;
__entry->pfn = fault->pfn | (fault->gfn & (KVM_PAGES_PER_HPAGE(fault->goal_level) - 1));
__entry->level = fault->goal_level;
+ __entry->access = access;
),

- TP_printk("gfn %llx pfn %llx level %d",
- __entry->gfn, __entry->pfn, __entry->level
+ TP_printk("gfn %llx pfn %llx level %d access %x",
+ __entry->gfn, __entry->pfn, __entry->level, __entry->access
)
);

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index f741f7d4cc2d..047400af924d 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -734,7 +734,7 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
*/
kvm_mmu_hugepage_adjust(vcpu, fault);

- trace_kvm_mmu_spte_requested(fault);
+ trace_kvm_mmu_spte_requested(fault, gw->pte_access);

for (; shadow_walk_okay(&it); shadow_walk_next(&it)) {
/*
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 7b1102d26f9c..5a2f8ce9a32b 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1185,9 +1185,9 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
}

if (unlikely(!fault->slot))
- new_spte = make_mmio_spte(vcpu, iter->gfn, ACC_ALL);
+ new_spte = make_mmio_spte(vcpu, iter->gfn, sp->role.access);
else
- wrprot = make_spte(vcpu, sp, fault->slot, ACC_ALL, iter->gfn,
+ wrprot = make_spte(vcpu, sp, fault->slot, sp->role.access, iter->gfn,
fault->pfn, iter->old_spte, fault->prefetch,
false, fault->map_writable, &new_spte);

@@ -1272,7 +1272,7 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)

kvm_mmu_hugepage_adjust(vcpu, fault);

- trace_kvm_mmu_spte_requested(fault);
+ trace_kvm_mmu_spte_requested(fault, root->role.access);

rcu_read_lock();

--
2.52.0