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KVM x86 MMU changes for 6.11

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- Don't allocate kvm_mmu_page.shadowed_translation for shadow pages that can't
    hole leafs SPTEs.
 
  - Unconditionally drop mmu_lock when allocating TDP MMU page tables for eager
    page splitting to avoid stalling vCPUs when splitting huge pages.
 
  - Misc cleanups
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Merge tag 'kvm-x86-mmu-6.11' of https://github.com/kvm-x86/linux into HEAD

KVM x86 MMU changes for 6.11

 - Don't allocate kvm_mmu_page.shadowed_translation for shadow pages that can't
   hold leafs SPTEs.

 - Unconditionally drop mmu_lock when allocating TDP MMU page tables for eager
   page splitting to avoid stalling vCPUs when splitting huge pages.

 - Misc cleanups
This commit is contained in:
Paolo Bonzini 2024-07-16 09:53:28 -04:00
commit 34b69edecb
3 changed files with 35 additions and 63 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
arch/x86/kvm/mmu/mmu.c
View File

@ -722,7 +722,7 @@ static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index)
if (sp->role.passthrough)
return sp->gfn;
if (!sp->role.direct)
if (sp->shadowed_translation)
return sp->shadowed_translation[index] >> PAGE_SHIFT;
return sp->gfn + (index << ((sp->role.level - 1) * SPTE_LEVEL_BITS));
@ -736,7 +736,7 @@ static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index)
*/
static u32 kvm_mmu_page_get_access(struct kvm_mmu_page *sp, int index)
{
if (sp_has_gptes(sp))
if (sp->shadowed_translation)
return sp->shadowed_translation[index] & ACC_ALL;
/*
@ -757,7 +757,7 @@ static u32 kvm_mmu_page_get_access(struct kvm_mmu_page *sp, int index)
static void kvm_mmu_page_set_translation(struct kvm_mmu_page *sp, int index,
gfn_t gfn, unsigned int access)
{
if (sp_has_gptes(sp)) {
if (sp->shadowed_translation) {
sp->shadowed_translation[index] = (gfn << PAGE_SHIFT) | access;
return;
}
@ -1700,7 +1700,6 @@ static void kvm_mmu_free_shadow_page(struct kvm_mmu_page *sp)
hlist_del(&sp->hash_link);
list_del(&sp->link);
free_page((unsigned long)sp->spt);
if (!sp->role.direct)
free_page((unsigned long)sp->shadowed_translation);
kmem_cache_free(mmu_page_header_cache, sp);
}
@ -2203,7 +2202,7 @@ static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm *kvm,
sp = kvm_mmu_memory_cache_alloc(caches->page_header_cache);
sp->spt = kvm_mmu_memory_cache_alloc(caches->shadow_page_cache);
if (!role.direct)
if (!role.direct && role.level <= KVM_MAX_HUGEPAGE_LEVEL)
sp->shadowed_translation = kvm_mmu_memory_cache_alloc(caches->shadowed_info_cache);
set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
@ -4609,7 +4608,10 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
if (WARN_ON_ONCE(error_code >> 32))
error_code = lower_32_bits(error_code);
/* Ensure the above sanity check also covers KVM-defined flags. */
/*
* Restrict KVM-defined flags to bits 63:32 so that it's impossible for
* them to conflict with #PF error codes, which are limited to 32 bits.
*/
BUILD_BUG_ON(lower_32_bits(PFERR_SYNTHETIC_MASK));
vcpu->arch.l1tf_flush_l1d = true;
@ -7049,7 +7051,6 @@ static unsigned long mmu_shrink_scan(struct shrinker *shrink,
list_for_each_entry(kvm, &vm_list, vm_list) {
int idx;
LIST_HEAD(invalid_list);
/*
* Never scan more than sc->nr_to_scan VM instances.

3
arch/x86/kvm/mmu/paging_tmpl.h
View File

@ -911,7 +911,8 @@ static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int
gpa_t pte_gpa;
gfn_t gfn;
if (WARN_ON_ONCE(sp->spt[i] == SHADOW_NONPRESENT_VALUE))
if (WARN_ON_ONCE(sp->spt[i] == SHADOW_NONPRESENT_VALUE ||
!sp->shadowed_translation))
return 0;
first_pte_gpa = FNAME(get_level1_sp_gpa)(sp);

76
arch/x86/kvm/mmu/tdp_mmu.c
View File

@ -1340,17 +1340,15 @@ bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm,
return spte_set;
}
static struct kvm_mmu_page *__tdp_mmu_alloc_sp_for_split(gfp_t gfp)
static struct kvm_mmu_page *tdp_mmu_alloc_sp_for_split(void)
{
struct kvm_mmu_page *sp;
gfp |= __GFP_ZERO;
sp = kmem_cache_alloc(mmu_page_header_cache, gfp);
sp = kmem_cache_zalloc(mmu_page_header_cache, GFP_KERNEL_ACCOUNT);
if (!sp)
return NULL;
sp->spt = (void *)__get_free_page(gfp);
sp->spt = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
if (!sp->spt) {
kmem_cache_free(mmu_page_header_cache, sp);
return NULL;
@ -1359,47 +1357,6 @@ static struct kvm_mmu_page *__tdp_mmu_alloc_sp_for_split(gfp_t gfp)
return sp;
}
static struct kvm_mmu_page *tdp_mmu_alloc_sp_for_split(struct kvm *kvm,
struct tdp_iter *iter,
bool shared)
{
struct kvm_mmu_page *sp;
kvm_lockdep_assert_mmu_lock_held(kvm, shared);
/*
* Since we are allocating while under the MMU lock we have to be
* careful about GFP flags. Use GFP_NOWAIT to avoid blocking on direct
* reclaim and to avoid making any filesystem callbacks (which can end
* up invoking KVM MMU notifiers, resulting in a deadlock).
*
* If this allocation fails we drop the lock and retry with reclaim
* allowed.
*/
sp = __tdp_mmu_alloc_sp_for_split(GFP_NOWAIT | __GFP_ACCOUNT);
if (sp)
return sp;
rcu_read_unlock();
if (shared)
read_unlock(&kvm->mmu_lock);
else
write_unlock(&kvm->mmu_lock);
iter->yielded = true;
sp = __tdp_mmu_alloc_sp_for_split(GFP_KERNEL_ACCOUNT);
if (shared)
read_lock(&kvm->mmu_lock);
else
write_lock(&kvm->mmu_lock);
rcu_read_lock();
return sp;
}
/* Note, the caller is responsible for initializing @sp. */
static int tdp_mmu_split_huge_page(struct kvm *kvm, struct tdp_iter *iter,
struct kvm_mmu_page *sp, bool shared)
@ -1446,7 +1403,6 @@ static int tdp_mmu_split_huge_pages_root(struct kvm *kvm,
{
struct kvm_mmu_page *sp = NULL;
struct tdp_iter iter;
int ret = 0;
rcu_read_lock();
@ -1470,16 +1426,30 @@ retry:
continue;
if (!sp) {
sp = tdp_mmu_alloc_sp_for_split(kvm, &iter, shared);
rcu_read_unlock();
if (shared)
read_unlock(&kvm->mmu_lock);
else
write_unlock(&kvm->mmu_lock);
sp = tdp_mmu_alloc_sp_for_split();
if (shared)
read_lock(&kvm->mmu_lock);
else
write_lock(&kvm->mmu_lock);
if (!sp) {
ret = -ENOMEM;
trace_kvm_mmu_split_huge_page(iter.gfn,
iter.old_spte,
iter.level, ret);
break;
iter.level, -ENOMEM);
return -ENOMEM;
}
if (iter.yielded)
rcu_read_lock();
iter.yielded = true;
continue;
}
@ -1501,7 +1471,7 @@ retry:
if (sp)
tdp_mmu_free_sp(sp);
return ret;
return 0;
}