[PATCH v5 08/21] KVM: x86/mmu: Move guest PT write-protection to account_shadowed()

David Matlack
2022-05-13T20:28:50Z

Move the code that write-protects newly-shadowed guest page tables into
account_shadowed(). This avoids a extra gfn-to-memslot lookup and is a
more logical place for this code to live. But most importantly, this
reduces kvm_mmu_alloc_shadow_page()'s reliance on having a struct
kvm_vcpu pointer, which will be necessary when creating new shadow pages
during VM ioctls for eager page splitting.

Note, it is safe to drop the role.level == PG_LEVEL_4K check since
account_shadowed() returns early if role.level > PG_LEVEL_4K.

No functional change intended.

Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
---
arch/x86/kvm/mmu/mmu.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4bbb6821f861..16001b019e1a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -792,6 +792,9 @@ static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
KVM_PAGE_TRACK_WRITE);

kvm_mmu_gfn_disallow_lpage(slot, gfn);
+
+ if (kvm_mmu_slot_gfn_write_protect(kvm, slot, gfn, PG_LEVEL_4K))
+ kvm_flush_remote_tlbs_with_address(kvm, gfn, 1);
}

void account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp)
@@ -2098,11 +2101,8 @@ static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm_vcpu *vcpu,
sp->gfn = gfn;
sp->role = role;
hlist_add_head(&sp->hash_link, sp_list);
- if (sp_has_gptes(sp)) {
+ if (sp_has_gptes(sp))
account_shadowed(vcpu->kvm, sp);
- if (role.level == PG_LEVEL_4K && kvm_vcpu_write_protect_gfn(vcpu, gfn))
- kvm_flush_remote_tlbs_with_address(vcpu->kvm, gfn, 1);
- }

return sp;
}
--
2.36.0.550.gb090851708-goog