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KVM: x86/mmu: Add helper to convert root hpa to shadow page

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Add a dedicated helper for converting a root hpa to a shadow page in
anticipation of using a "dummy" root to handle the scenario where KVM
needs to load a valid shadow root (from hardware's perspective), but
the guest doesn't have a visible root to shadow.  Similar to PAE roots,
the dummy root won't have an associated kvm_mmu_page and will need special
handling when finding a shadow page given a root.

Opportunistically retrieve the root shadow page in kvm_mmu_sync_roots()
*after* verifying the root is unsync (the dummy root can never be unsync).

Link: https://lore.kernel.org/r/20230729005200.1057358-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2023-07-28 17:51:56 -07:00 committed by Paolo Bonzini
parent 09c8726ffa
commit c5f2d5645f
3 changed files with 23 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
arch/x86/kvm/mmu/mmu.c
View File

@ -3543,11 +3543,7 @@ static void mmu_free_root_page(struct kvm *kvm, hpa_t *root_hpa,
if (!VALID_PAGE(*root_hpa))
return;
/*
* The "root" may be a special root, e.g. a PAE entry, treat it as a
* SPTE to ensure any non-PA bits are dropped.
*/
sp = spte_to_child_sp(*root_hpa);
sp = root_to_sp(*root_hpa);
if (WARN_ON_ONCE(!sp))
return;
@ -3593,7 +3589,7 @@ void kvm_mmu_free_roots(struct kvm *kvm, struct kvm_mmu *mmu,
&invalid_list);
if (free_active_root) {
if (to_shadow_page(mmu->root.hpa)) {
if (root_to_sp(mmu->root.hpa)) {
mmu_free_root_page(kvm, &mmu->root.hpa, &invalid_list);
} else if (mmu->pae_root) {
for (i = 0; i < 4; ++i) {
@ -3617,6 +3613,7 @@ EXPORT_SYMBOL_GPL(kvm_mmu_free_roots);
void kvm_mmu_free_guest_mode_roots(struct kvm *kvm, struct kvm_mmu *mmu)
{
unsigned long roots_to_free = 0;
struct kvm_mmu_page *sp;
hpa_t root_hpa;
int i;
@ -3631,8 +3628,8 @@ void kvm_mmu_free_guest_mode_roots(struct kvm *kvm, struct kvm_mmu *mmu)
if (!VALID_PAGE(root_hpa))
continue;
if (!to_shadow_page(root_hpa) ||
to_shadow_page(root_hpa)->role.guest_mode)
sp = root_to_sp(root_hpa);
if (!sp || sp->role.guest_mode)
roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
}
@ -3987,7 +3984,7 @@ static bool is_unsync_root(hpa_t root)
* requirement isn't satisfied.
*/
smp_rmb();
sp = to_shadow_page(root);
sp = root_to_sp(root);
/*
* PAE roots (somewhat arbitrarily) aren't backed by shadow pages, the
@ -4017,11 +4014,12 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
if (vcpu->arch.mmu->cpu_role.base.level >= PT64_ROOT_4LEVEL) {
hpa_t root = vcpu->arch.mmu->root.hpa;
sp = to_shadow_page(root);
if (!is_unsync_root(root))
return;
sp = root_to_sp(root);
write_lock(&vcpu->kvm->mmu_lock);
mmu_sync_children(vcpu, sp, true);
write_unlock(&vcpu->kvm->mmu_lock);
@ -4351,7 +4349,7 @@ static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
static bool is_page_fault_stale(struct kvm_vcpu *vcpu,
struct kvm_page_fault *fault)
{
struct kvm_mmu_page *sp = to_shadow_page(vcpu->arch.mmu->root.hpa);
struct kvm_mmu_page *sp = root_to_sp(vcpu->arch.mmu->root.hpa);
/* Special roots, e.g. pae_root, are not backed by shadow pages. */
if (sp && is_obsolete_sp(vcpu->kvm, sp))
@ -4531,7 +4529,7 @@ static inline bool is_root_usable(struct kvm_mmu_root_info *root, gpa_t pgd,
{
return (role.direct || pgd == root->pgd) &&
VALID_PAGE(root->hpa) &&
role.word == to_shadow_page(root->hpa)->role.word;
role.word == root_to_sp(root->hpa)->role.word;
}
/*
@ -4605,7 +4603,7 @@ static bool fast_pgd_switch(struct kvm *kvm, struct kvm_mmu *mmu,
* having to deal with PDPTEs. We may add support for 32-bit hosts/VMs
* later if necessary.
*/
if (VALID_PAGE(mmu->root.hpa) && !to_shadow_page(mmu->root.hpa))
if (VALID_PAGE(mmu->root.hpa) && !root_to_sp(mmu->root.hpa))
kvm_mmu_free_roots(kvm, mmu, KVM_MMU_ROOT_CURRENT);
if (VALID_PAGE(mmu->root.hpa))
@ -4653,7 +4651,7 @@ void kvm_mmu_new_pgd(struct kvm_vcpu *vcpu, gpa_t new_pgd)
*/
if (!new_role.direct)
__clear_sp_write_flooding_count(
to_shadow_page(vcpu->arch.mmu->root.hpa));
root_to_sp(vcpu->arch.mmu->root.hpa));
}
EXPORT_SYMBOL_GPL(kvm_mmu_new_pgd);
@ -5508,7 +5506,7 @@ static bool is_obsolete_root(struct kvm *kvm, hpa_t root_hpa)
* (c) KVM doesn't track previous roots for PAE paging, and the guest
* is unlikely to zap an in-use PGD.
*/
sp = to_shadow_page(root_hpa);
sp = root_to_sp(root_hpa);
return !sp || is_obsolete_sp(kvm, sp);
}

9
arch/x86/kvm/mmu/spte.h
View File

@ -236,6 +236,15 @@ static inline struct kvm_mmu_page *sptep_to_sp(u64 *sptep)
return to_shadow_page(__pa(sptep));
}
static inline struct kvm_mmu_page *root_to_sp(hpa_t root)
{
/*
* The "root" may be a special root, e.g. a PAE entry, treat it as a
* SPTE to ensure any non-PA bits are dropped.
*/
return spte_to_child_sp(root);
}
static inline bool is_mmio_spte(u64 spte)
{
return (spte & shadow_mmio_mask) == shadow_mmio_value &&

2
arch/x86/kvm/mmu/tdp_mmu.c
View File

@ -689,7 +689,7 @@ static inline void tdp_mmu_iter_set_spte(struct kvm *kvm, struct tdp_iter *iter,
else
#define tdp_mmu_for_each_pte(_iter, _mmu, _start, _end) \
for_each_tdp_pte(_iter, to_shadow_page(_mmu->root.hpa), _start, _end)
for_each_tdp_pte(_iter, root_to_sp(_mmu->root.hpa), _start, _end)
/*
* Yield if the MMU lock is contended or this thread needs to return control