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x86/kvm: Cache gfn to pfn translation 

__kvm_map_gfn()'s call to gfn_to_pfn_memslot() is
* relatively expensive
* in certain cases (such as when done from atomic context) cannot be called

Stashing gfn-to-pfn mapping should help with both cases.

This is part of CVE-2019-3016.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Boris Ostrovsky 2019-12-05 01:30:51 +00:00 committed by Paolo Bonzini
parent 1eff70a9ab
commit 917248144d
5 changed files with 103 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/x86/include/asm/kvm_host.h
View File

@ -689,6 +689,7 @@ struct kvm_vcpu_arch {
u64 last_steal;
struct gfn_to_hva_cache stime;
struct kvm_steal_time steal;
struct gfn_to_pfn_cache cache;
} st;
u64 tsc_offset;

10
arch/x86/kvm/x86.c
View File

@ -9088,6 +9088,9 @@ static void fx_init(struct kvm_vcpu *vcpu)
void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
{
void *wbinvd_dirty_mask = vcpu->arch.wbinvd_dirty_mask;
struct gfn_to_pfn_cache *cache = &vcpu->arch.st.cache;
kvm_release_pfn(cache->pfn, cache->dirty, cache);
kvmclock_reset(vcpu);
@ -9761,11 +9764,18 @@ out_free:
void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen)
{
struct kvm_vcpu *vcpu;
int i;
/*
* memslots->generation has been incremented.
* mmio generation may have reached its maximum value.
*/
kvm_mmu_invalidate_mmio_sptes(kvm, gen);
/* Force re-initialization of steal_time cache */
kvm_for_each_vcpu(i, vcpu, kvm)
kvm_vcpu_kick(vcpu);
}
int kvm_arch_prepare_memory_region(struct kvm *kvm,

7
include/linux/kvm_host.h
View File

@ -723,6 +723,7 @@ void kvm_set_pfn_dirty(kvm_pfn_t pfn);
void kvm_set_pfn_accessed(kvm_pfn_t pfn);
void kvm_get_pfn(kvm_pfn_t pfn);
void kvm_release_pfn(kvm_pfn_t pfn, bool dirty, struct gfn_to_pfn_cache *cache);
int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
int len);
int kvm_read_guest_atomic(struct kvm *kvm, gpa_t gpa, void *data,
@ -775,10 +776,12 @@ struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn
kvm_pfn_t kvm_vcpu_gfn_to_pfn_atomic(struct kvm_vcpu *vcpu, gfn_t gfn);
kvm_pfn_t kvm_vcpu_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn);
int kvm_vcpu_map(struct kvm_vcpu *vcpu, gpa_t gpa, struct kvm_host_map *map);
int kvm_map_gfn(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map);
int kvm_map_gfn(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map,
struct gfn_to_pfn_cache *cache, bool atomic);
struct page *kvm_vcpu_gfn_to_page(struct kvm_vcpu *vcpu, gfn_t gfn);
void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty);
int kvm_unmap_gfn(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty);
int kvm_unmap_gfn(struct kvm_vcpu *vcpu, struct kvm_host_map *map,
struct gfn_to_pfn_cache *cache, bool dirty, bool atomic);
unsigned long kvm_vcpu_gfn_to_hva(struct kvm_vcpu *vcpu, gfn_t gfn);
unsigned long kvm_vcpu_gfn_to_hva_prot(struct kvm_vcpu *vcpu, gfn_t gfn, bool *writable);
int kvm_vcpu_read_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn, void *data, int offset,

9
include/linux/kvm_types.h
View File

@ -18,7 +18,7 @@ struct kvm_memslots;
enum kvm_mr_change;
#include <asm/types.h>
#include <linux/types.h>
/*
* Address types:
@ -51,4 +51,11 @@ struct gfn_to_hva_cache {
struct kvm_memory_slot *memslot;
};
struct gfn_to_pfn_cache {
u64 generation;
gfn_t gfn;
kvm_pfn_t pfn;
bool dirty;
};
#endif /* __KVM_TYPES_H__ */

94
virt/kvm/kvm_main.c
View File

@ -1821,27 +1821,72 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
}
EXPORT_SYMBOL_GPL(gfn_to_page);
void kvm_release_pfn(kvm_pfn_t pfn, bool dirty, struct gfn_to_pfn_cache *cache)
{
if (pfn == 0)
return;
if (cache)
cache->pfn = cache->gfn = 0;
if (dirty)
kvm_release_pfn_dirty(pfn);
else
kvm_release_pfn_clean(pfn);
}
static void kvm_cache_gfn_to_pfn(struct kvm_memory_slot *slot, gfn_t gfn,
struct gfn_to_pfn_cache *cache, u64 gen)
{
kvm_release_pfn(cache->pfn, cache->dirty, cache);
cache->pfn = gfn_to_pfn_memslot(slot, gfn);
cache->gfn = gfn;
cache->dirty = false;
cache->generation = gen;
}
static int __kvm_map_gfn(struct kvm_memslots *slots, gfn_t gfn,
struct kvm_host_map *map)
struct kvm_host_map *map,
struct gfn_to_pfn_cache *cache,
bool atomic)
{
kvm_pfn_t pfn;
void *hva = NULL;
struct page *page = KVM_UNMAPPED_PAGE;
struct kvm_memory_slot *slot = __gfn_to_memslot(slots, gfn);
u64 gen = slots->generation;
if (!map)
return -EINVAL;
if (cache) {
if (!cache->pfn || cache->gfn != gfn ||
cache->generation != gen) {
if (atomic)
return -EAGAIN;
kvm_cache_gfn_to_pfn(slot, gfn, cache, gen);
}
pfn = cache->pfn;
} else {
if (atomic)
return -EAGAIN;
pfn = gfn_to_pfn_memslot(slot, gfn);
}
if (is_error_noslot_pfn(pfn))
return -EINVAL;
if (pfn_valid(pfn)) {
page = pfn_to_page(pfn);
if (atomic)
hva = kmap_atomic(page);
else
hva = kmap(page);
#ifdef CONFIG_HAS_IOMEM
} else {
} else if (!atomic) {
hva = memremap(pfn_to_hpa(pfn), PAGE_SIZE, MEMREMAP_WB);
} else {
return -EINVAL;
#endif
}
@ -1856,20 +1901,25 @@ static int __kvm_map_gfn(struct kvm_memslots *slots, gfn_t gfn,
return 0;
}
int kvm_map_gfn(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
int kvm_map_gfn(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map,
struct gfn_to_pfn_cache *cache, bool atomic)
{
return __kvm_map_gfn(kvm_memslots(vcpu->kvm), gfn, map);
return __kvm_map_gfn(kvm_memslots(vcpu->kvm), gfn, map,
cache, atomic);
}
EXPORT_SYMBOL_GPL(kvm_map_gfn);
int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
{
return __kvm_map_gfn(kvm_vcpu_memslots(vcpu), gfn, map);
return __kvm_map_gfn(kvm_vcpu_memslots(vcpu), gfn, map,
NULL, false);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_map);
static void __kvm_unmap_gfn(struct kvm_memory_slot *memslot,
struct kvm_host_map *map, bool dirty)
struct kvm_host_map *map,
struct gfn_to_pfn_cache *cache,
bool dirty, bool atomic)
{
if (!map)
return;
@ -1877,34 +1927,44 @@ static void __kvm_unmap_gfn(struct kvm_memory_slot *memslot,
if (!map->hva)
return;
if (map->page != KVM_UNMAPPED_PAGE)
kunmap(map->page);
#ifdef CONFIG_HAS_IOMEM
if (map->page != KVM_UNMAPPED_PAGE) {
if (atomic)
kunmap_atomic(map->hva);
else
kunmap(map->page);
}
#ifdef CONFIG_HAS_IOMEM
else if (!atomic)
memunmap(map->hva);
else
WARN_ONCE(1, "Unexpected unmapping in atomic context");
#endif
if (dirty) {
if (dirty)
mark_page_dirty_in_slot(memslot, map->gfn);
kvm_release_pfn_dirty(map->pfn);
} else {
kvm_release_pfn_clean(map->pfn);
}
if (cache)
cache->dirty |= dirty;
else
kvm_release_pfn(map->pfn, dirty, NULL);
map->hva = NULL;
map->page = NULL;
}
int kvm_unmap_gfn(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty)
int kvm_unmap_gfn(struct kvm_vcpu *vcpu, struct kvm_host_map *map,
struct gfn_to_pfn_cache *cache, bool dirty, bool atomic)
{
__kvm_unmap_gfn(gfn_to_memslot(vcpu->kvm, map->gfn), map, dirty);
__kvm_unmap_gfn(gfn_to_memslot(vcpu->kvm, map->gfn), map,
cache, dirty, atomic);
return 0;
}
EXPORT_SYMBOL_GPL(kvm_unmap_gfn);
void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty)
{
__kvm_unmap_gfn(kvm_vcpu_gfn_to_memslot(vcpu, map->gfn), map, dirty);
__kvm_unmap_gfn(kvm_vcpu_gfn_to_memslot(vcpu, map->gfn), map, NULL,
dirty, false);
}
EXPORT_SYMBOL_GPL(kvm_vcpu_unmap);