[PATCH 5.5 248/367] x86/kvm: Cache gfn to pfn translation

Greg Kroah-Hartman
2020-02-10T12:48:59Z

From: Boris Ostrovsky <boris.ostrovsky@oracle.com>

commit 917248144db5d7320655dbb41d3af0b8a0f3d589 upstream.

__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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/include/asm/kvm_host.h | 1
arch/x86/kvm/x86.c | 10 ++++
include/linux/kvm_host.h | 7 ++
include/linux/kvm_types.h | 9 +++
virt/kvm/kvm_main.c | 98 ++++++++++++++++++++++++++++++++--------
5 files changed, 103 insertions(+), 22 deletions(-)

--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -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;
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9111,6 +9111,9 @@ static void fx_init(struct kvm_vcpu *vcp
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);

@@ -9784,11 +9787,18 @@ 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,
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -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_
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,
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -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__ */
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1821,27 +1821,72 @@ struct page *gfn_to_page(struct kvm *kvm
}
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;

- pfn = gfn_to_pfn_memslot(slot, gfn);
+ 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);
- hva = kmap(page);
+ 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_mems
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_m
if (!map->hva)
return;

- if (map->page != KVM_UNMAPPED_PAGE)
- kunmap(map->page);
+ if (map->page != KVM_UNMAPPED_PAGE) {
+ if (atomic)
+ kunmap_atomic(map->hva);
+ else
+ kunmap(map->page);
+ }
#ifdef CONFIG_HAS_IOMEM
- else
+ 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);