Commit 61f94478 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini

KVM: x86/mmu: Set disallowed_nx_huge_page in TDP MMU before setting SPTE

Set nx_huge_page_disallowed in TDP MMU shadow pages before making the SP
visible to other readers, i.e. before setting its SPTE.  This will allow
KVM to query the flag when determining if a shadow page can be replaced
by a NX huge page without violating the rules of the mitigation.

Note, the shadow/legacy MMU holds mmu_lock for write, so it's impossible
for another CPU to see a shadow page without an up-to-date
nx_huge_page_disallowed, i.e. only the TDP MMU needs the complicated
dance.
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Reviewed-by: default avatarDavid Matlack <dmatlack@google.com>
Reviewed-by: default avatarYan Zhao <yan.y.zhao@intel.com>
Message-Id: <20221019165618.927057-5-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent b5b0977f
......@@ -803,11 +803,8 @@ static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
kvm_flush_remote_tlbs_with_address(kvm, gfn, 1);
}
void account_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp,
bool nx_huge_page_possible)
void track_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
sp->nx_huge_page_disallowed = true;
/*
* If it's possible to replace the shadow page with an NX huge page,
* i.e. if the shadow page is the only thing currently preventing KVM
......@@ -816,8 +813,7 @@ void account_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp,
* on the list if KVM is reusing an existing shadow page, i.e. if KVM
* links a shadow page at multiple points.
*/
if (!nx_huge_page_possible ||
!list_empty(&sp->possible_nx_huge_page_link))
if (!list_empty(&sp->possible_nx_huge_page_link))
return;
++kvm->stat.nx_lpage_splits;
......@@ -825,6 +821,15 @@ void account_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp,
&kvm->arch.possible_nx_huge_pages);
}
static void account_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp,
bool nx_huge_page_possible)
{
sp->nx_huge_page_disallowed = true;
if (nx_huge_page_possible)
track_possible_nx_huge_page(kvm, sp);
}
static void unaccount_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
{
struct kvm_memslots *slots;
......@@ -842,10 +847,8 @@ static void unaccount_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
kvm_mmu_gfn_allow_lpage(slot, gfn);
}
void unaccount_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
void untrack_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
sp->nx_huge_page_disallowed = false;
if (list_empty(&sp->possible_nx_huge_page_link))
return;
......@@ -853,6 +856,13 @@ void unaccount_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
list_del_init(&sp->possible_nx_huge_page_link);
}
static void unaccount_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
sp->nx_huge_page_disallowed = false;
untrack_possible_nx_huge_page(kvm, sp);
}
static struct kvm_memory_slot *
gfn_to_memslot_dirty_bitmap(struct kvm_vcpu *vcpu, gfn_t gfn,
bool no_dirty_log)
......
......@@ -328,8 +328,7 @@ void disallowed_hugepage_adjust(struct kvm_page_fault *fault, u64 spte, int cur_
void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc);
void account_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp,
bool nx_huge_page_possible);
void unaccount_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp);
void track_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp);
void untrack_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp);
#endif /* __KVM_X86_MMU_INTERNAL_H */
......@@ -403,8 +403,11 @@ static void tdp_mmu_unlink_sp(struct kvm *kvm, struct kvm_mmu_page *sp,
lockdep_assert_held_write(&kvm->mmu_lock);
list_del(&sp->link);
if (sp->nx_huge_page_disallowed)
unaccount_nx_huge_page(kvm, sp);
if (sp->nx_huge_page_disallowed) {
sp->nx_huge_page_disallowed = false;
untrack_possible_nx_huge_page(kvm, sp);
}
if (shared)
spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
......@@ -1118,16 +1121,13 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
* @kvm: kvm instance
* @iter: a tdp_iter instance currently on the SPTE that should be set
* @sp: The new TDP page table to install.
* @account_nx: True if this page table is being installed to split a
* non-executable huge page.
* @shared: This operation is running under the MMU lock in read mode.
*
* Returns: 0 if the new page table was installed. Non-0 if the page table
* could not be installed (e.g. the atomic compare-exchange failed).
*/
static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter,
struct kvm_mmu_page *sp, bool account_nx,
bool shared)
struct kvm_mmu_page *sp, bool shared)
{
u64 spte = make_nonleaf_spte(sp->spt, !kvm_ad_enabled());
int ret = 0;
......@@ -1142,8 +1142,6 @@ static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter,
spin_lock(&kvm->arch.tdp_mmu_pages_lock);
list_add(&sp->link, &kvm->arch.tdp_mmu_pages);
if (account_nx)
account_nx_huge_page(kvm, sp, true);
spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
tdp_account_mmu_page(kvm, sp);
......@@ -1157,6 +1155,7 @@ static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter,
int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
struct kvm_mmu *mmu = vcpu->arch.mmu;
struct kvm *kvm = vcpu->kvm;
struct tdp_iter iter;
struct kvm_mmu_page *sp;
int ret;
......@@ -1193,9 +1192,6 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
}
if (!is_shadow_present_pte(iter.old_spte)) {
bool account_nx = fault->huge_page_disallowed &&
fault->req_level >= iter.level;
/*
* If SPTE has been frozen by another thread, just
* give up and retry, avoiding unnecessary page table
......@@ -1207,10 +1203,19 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
sp = tdp_mmu_alloc_sp(vcpu);
tdp_mmu_init_child_sp(sp, &iter);
if (tdp_mmu_link_sp(vcpu->kvm, &iter, sp, account_nx, true)) {
sp->nx_huge_page_disallowed = fault->huge_page_disallowed;
if (tdp_mmu_link_sp(kvm, &iter, sp, true)) {
tdp_mmu_free_sp(sp);
break;
}
if (fault->huge_page_disallowed &&
fault->req_level >= iter.level) {
spin_lock(&kvm->arch.tdp_mmu_pages_lock);
track_possible_nx_huge_page(kvm, sp);
spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
}
}
}
......@@ -1498,7 +1503,7 @@ static int tdp_mmu_split_huge_page(struct kvm *kvm, struct tdp_iter *iter,
* correctness standpoint since the translation will be the same either
* way.
*/
ret = tdp_mmu_link_sp(kvm, iter, sp, false, shared);
ret = tdp_mmu_link_sp(kvm, iter, sp, shared);
if (ret)
goto out;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment