In shadow page table, only leaf SPs may be marked as unsync;
instead, for non-leaf SPs, we store the number of unsynced
children in unsync_children. Therefore, in kvm_mmu_sync_root(),
sp->unsync shall always be zero for the root SP and there is
no need to check it. Remove the check, and add a warning
inside mmu_sync_children() to assert that the flags are used
properly.
While at it, move the warning from mmu_need_write_protect()
to kvm_unsync_page().
Co-developed-by: Sean Christopherson <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
Signed-off-by: Yu Zhang <[email protected]>
---
arch/x86/kvm/mmu/mmu.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 86af58294272..5f482af125b4 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1995,6 +1995,12 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu,
LIST_HEAD(invalid_list);
bool flush = false;
+ /*
+ * Only 4k SPTEs can directly be made unsync, the parent pages
+ * should never be unsyc'd.
+ */
+ WARN_ON_ONCE(parent->unsync);
+
while (mmu_unsync_walk(parent, &pages)) {
bool protected = false;
@@ -2502,6 +2508,8 @@ EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page);
static void kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
+ WARN_ON(sp->role.level != PG_LEVEL_4K);
+
trace_kvm_mmu_unsync_page(sp);
++vcpu->kvm->stat.mmu_unsync;
sp->unsync = 1;
@@ -2524,7 +2532,6 @@ bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
if (sp->unsync)
continue;
- WARN_ON(sp->role.level != PG_LEVEL_4K);
kvm_unsync_page(vcpu, sp);
}
@@ -3406,8 +3413,7 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
* mmu_need_write_protect() describe what could go wrong if this
* requirement isn't satisfied.
*/
- if (!smp_load_acquire(&sp->unsync) &&
- !smp_load_acquire(&sp->unsync_children))
+ if (!smp_load_acquire(&sp->unsync_children))
return;
write_lock(&vcpu->kvm->mmu_lock);
--
2.17.1
Sorry, forget the change log:
Changes in V3:
- fixed a bug in warnings inside mmu_sync_children().
- commit message changes based on Paolo's suggestion.
- added Co-developed-by: Sean Christopherson <[email protected]>
Changes in V2:
- warnings added based on Sean's suggestion.
On Wed, Feb 10, 2021 at 01:01:11AM +0800, Yu Zhang wrote:
> In shadow page table, only leaf SPs may be marked as unsync;
> instead, for non-leaf SPs, we store the number of unsynced
> children in unsync_children. Therefore, in kvm_mmu_sync_root(),
> sp->unsync shall always be zero for the root SP and there is
> no need to check it. Remove the check, and add a warning
> inside mmu_sync_children() to assert that the flags are used
> properly.
>
> While at it, move the warning from mmu_need_write_protect()
> to kvm_unsync_page().
>
> Co-developed-by: Sean Christopherson <[email protected]>
> Signed-off-by: Sean Christopherson <[email protected]>
> Signed-off-by: Paolo Bonzini <[email protected]>
> Signed-off-by: Yu Zhang <[email protected]>
> ---
> arch/x86/kvm/mmu/mmu.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 86af58294272..5f482af125b4 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -1995,6 +1995,12 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu,
> LIST_HEAD(invalid_list);
> bool flush = false;
>
> + /*
> + * Only 4k SPTEs can directly be made unsync, the parent pages
> + * should never be unsyc'd.
> + */
> + WARN_ON_ONCE(parent->unsync);
> +
> while (mmu_unsync_walk(parent, &pages)) {
> bool protected = false;
>
> @@ -2502,6 +2508,8 @@ EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page);
>
> static void kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
> {
> + WARN_ON(sp->role.level != PG_LEVEL_4K);
> +
> trace_kvm_mmu_unsync_page(sp);
> ++vcpu->kvm->stat.mmu_unsync;
> sp->unsync = 1;
> @@ -2524,7 +2532,6 @@ bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
> if (sp->unsync)
> continue;
>
> - WARN_ON(sp->role.level != PG_LEVEL_4K);
> kvm_unsync_page(vcpu, sp);
> }
>
> @@ -3406,8 +3413,7 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
> * mmu_need_write_protect() describe what could go wrong if this
> * requirement isn't satisfied.
> */
> - if (!smp_load_acquire(&sp->unsync) &&
> - !smp_load_acquire(&sp->unsync_children))
> + if (!smp_load_acquire(&sp->unsync_children))
> return;
>
> write_lock(&vcpu->kvm->mmu_lock);
> --
> 2.17.1
>
On 09/02/21 18:01, Yu Zhang wrote:
> In shadow page table, only leaf SPs may be marked as unsync;
> instead, for non-leaf SPs, we store the number of unsynced
> children in unsync_children. Therefore, in kvm_mmu_sync_root(),
> sp->unsync shall always be zero for the root SP and there is
> no need to check it. Remove the check, and add a warning
> inside mmu_sync_children() to assert that the flags are used
> properly.
>
> While at it, move the warning from mmu_need_write_protect()
> to kvm_unsync_page().
>
> Co-developed-by: Sean Christopherson <[email protected]>
> Signed-off-by: Sean Christopherson <[email protected]>
> Signed-off-by: Paolo Bonzini <[email protected]>
> Signed-off-by: Yu Zhang <[email protected]>
> ---
> arch/x86/kvm/mmu/mmu.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 86af58294272..5f482af125b4 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -1995,6 +1995,12 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu,
> LIST_HEAD(invalid_list);
> bool flush = false;
>
> + /*
> + * Only 4k SPTEs can directly be made unsync, the parent pages
> + * should never be unsyc'd.
> + */
> + WARN_ON_ONCE(parent->unsync);
> +
> while (mmu_unsync_walk(parent, &pages)) {
> bool protected = false;
>
> @@ -2502,6 +2508,8 @@ EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page);
>
> static void kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
> {
> + WARN_ON(sp->role.level != PG_LEVEL_4K);
> +
> trace_kvm_mmu_unsync_page(sp);
> ++vcpu->kvm->stat.mmu_unsync;
> sp->unsync = 1;
> @@ -2524,7 +2532,6 @@ bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
> if (sp->unsync)
> continue;
>
> - WARN_ON(sp->role.level != PG_LEVEL_4K);
> kvm_unsync_page(vcpu, sp);
> }
>
> @@ -3406,8 +3413,7 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
> * mmu_need_write_protect() describe what could go wrong if this
> * requirement isn't satisfied.
> */
> - if (!smp_load_acquire(&sp->unsync) &&
> - !smp_load_acquire(&sp->unsync_children))
> + if (!smp_load_acquire(&sp->unsync_children))
> return;
>
> write_lock(&vcpu->kvm->mmu_lock);
>
Queued, thanks.
Paolo