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KVM: MMU: fast invalidate all mmio sptes

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This patch tries to introduce a very simple and scale way to invalidate
all mmio sptes - it need not walk any shadow pages and hold mmu-lock

KVM maintains a global mmio valid generation-number which is stored in
kvm->memslots.generation and every mmio spte stores the current global
generation-number into his available bits when it is created

When KVM need zap all mmio sptes, it just simply increase the global
generation-number. When guests do mmio access, KVM intercepts a MMIO #PF
then it walks the shadow page table and get the mmio spte. If the
generation-number on the spte does not equal the global generation-number,
it will go to the normal #PF handler to update the mmio spte

Since 19 bits are used to store generation-number on mmio spte, we zap all
mmio sptes when the number is round

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Xiao Guangrong 2013-06-07 16:51:26 +08:00 committed by Gleb Natapov
parent b37fbea6ce
commit f8f559422b
6 changed files with 61 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/include/asm/kvm_host.h
View File

@ -773,7 +773,7 @@ void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
struct kvm_memory_slot *slot,
gfn_t gfn_offset, unsigned long mask);
void kvm_mmu_zap_all(struct kvm *kvm);
void kvm_mmu_zap_mmio_sptes(struct kvm *kvm);
void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm);
unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm);
void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages);

54
arch/x86/kvm/mmu.c
View File

@ -205,9 +205,11 @@ EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask);
#define MMIO_SPTE_GEN_LOW_SHIFT 3
#define MMIO_SPTE_GEN_HIGH_SHIFT 52
#define MMIO_GEN_SHIFT 19
#define MMIO_GEN_LOW_SHIFT 9
#define MMIO_GEN_LOW_MASK ((1 << MMIO_GEN_LOW_SHIFT) - 1)
#define MMIO_MAX_GEN ((1 << 19) - 1)
#define MMIO_GEN_MASK ((1 << MMIO_GEN_SHIFT) - 1)
#define MMIO_MAX_GEN ((1 << MMIO_GEN_SHIFT) - 1)
static u64 generation_mmio_spte_mask(unsigned int gen)
{
@ -231,17 +233,23 @@ static unsigned int get_mmio_spte_generation(u64 spte)
return gen;
}
static unsigned int kvm_current_mmio_generation(struct kvm *kvm)
{
return kvm_memslots(kvm)->generation & MMIO_GEN_MASK;
}
static void mark_mmio_spte(struct kvm *kvm, u64 *sptep, u64 gfn,
unsigned access)
{
struct kvm_mmu_page *sp = page_header(__pa(sptep));
u64 mask = generation_mmio_spte_mask(0);
unsigned int gen = kvm_current_mmio_generation(kvm);
u64 mask = generation_mmio_spte_mask(gen);
access &= ACC_WRITE_MASK | ACC_USER_MASK;
mask |= shadow_mmio_mask | access | gfn << PAGE_SHIFT;
sp->mmio_cached = true;
trace_mark_mmio_spte(sptep, gfn, access, 0);
trace_mark_mmio_spte(sptep, gfn, access, gen);
mmu_spte_set(sptep, mask);
}
@ -273,6 +281,12 @@ static bool set_mmio_spte(struct kvm *kvm, u64 *sptep, gfn_t gfn,
return false;
}
static bool check_mmio_spte(struct kvm *kvm, u64 spte)
{
return likely(get_mmio_spte_generation(spte) ==
kvm_current_mmio_generation(kvm));
}
static inline u64 rsvd_bits(int s, int e)
{
return ((1ULL << (e - s + 1)) - 1) << s;
@ -3237,6 +3251,9 @@ int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct)
gfn_t gfn = get_mmio_spte_gfn(spte);
unsigned access = get_mmio_spte_access(spte);
if (!check_mmio_spte(vcpu->kvm, spte))
return RET_MMIO_PF_INVALID;
if (direct)
addr = 0;
@ -3278,8 +3295,12 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
pgprintk("%s: gva %lx error %x\n", __func__, gva, error_code);
if (unlikely(error_code & PFERR_RSVD_MASK))
return handle_mmio_page_fault(vcpu, gva, error_code, true);
if (unlikely(error_code & PFERR_RSVD_MASK)) {
r = handle_mmio_page_fault(vcpu, gva, error_code, true);
if (likely(r != RET_MMIO_PF_INVALID))
return r;
}
r = mmu_topup_memory_caches(vcpu);
if (r)
@ -3355,8 +3376,12 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
ASSERT(vcpu);
ASSERT(VALID_PAGE(vcpu->arch.mmu.root_hpa));
if (unlikely(error_code & PFERR_RSVD_MASK))
return handle_mmio_page_fault(vcpu, gpa, error_code, true);
if (unlikely(error_code & PFERR_RSVD_MASK)) {
r = handle_mmio_page_fault(vcpu, gpa, error_code, true);
if (likely(r != RET_MMIO_PF_INVALID))
return r;
}
r = mmu_topup_memory_caches(vcpu);
if (r)
@ -4329,7 +4354,7 @@ void kvm_mmu_invalidate_zap_all_pages(struct kvm *kvm)
spin_unlock(&kvm->mmu_lock);
}
void kvm_mmu_zap_mmio_sptes(struct kvm *kvm)
static void kvm_mmu_zap_mmio_sptes(struct kvm *kvm)
{
struct kvm_mmu_page *sp, *node;
LIST_HEAD(invalid_list);
@ -4352,6 +4377,19 @@ static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
}
void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm)
{
/*
* The very rare case: if the generation-number is round,
* zap all shadow pages.
*
* The max value is MMIO_MAX_GEN - 1 since it is not called
* when mark memslot invalid.
*/
if (unlikely(kvm_current_mmio_generation(kvm) >= (MMIO_MAX_GEN - 1)))
kvm_mmu_zap_mmio_sptes(kvm);
}
static int mmu_shrink(struct shrinker *shrink, struct shrink_control *sc)
{
struct kvm *kvm;

5
arch/x86/kvm/mmu.h
View File

@ -56,12 +56,15 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask);
/*
* Return values of handle_mmio_page_fault_common:
* RET_MMIO_PF_EMULATE: it is a real mmio page fault, emulate the instruction
* directly.
* directly.
* RET_MMIO_PF_INVALID: invalid spte is detected then let the real page
* fault path update the mmio spte.
* RET_MMIO_PF_RETRY: let CPU fault again on the address.
* RET_MMIO_PF_BUG: bug is detected.
*/
enum {
RET_MMIO_PF_EMULATE = 1,
RET_MMIO_PF_INVALID = 2,
RET_MMIO_PF_RETRY = 0,
RET_MMIO_PF_BUG = -1
};

7
arch/x86/kvm/paging_tmpl.h
View File

@ -552,9 +552,12 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
if (unlikely(error_code & PFERR_RSVD_MASK))
return handle_mmio_page_fault(vcpu, addr, error_code,
if (unlikely(error_code & PFERR_RSVD_MASK)) {
r = handle_mmio_page_fault(vcpu, addr, error_code,
mmu_is_nested(vcpu));
if (likely(r != RET_MMIO_PF_INVALID))
return r;
};
r = mmu_topup_memory_caches(vcpu);
if (r)

4
arch/x86/kvm/vmx.c
View File

@ -5369,6 +5369,10 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu)
if (likely(ret == RET_MMIO_PF_EMULATE))
return x86_emulate_instruction(vcpu, gpa, 0, NULL, 0) ==
EMULATE_DONE;
if (unlikely(ret == RET_MMIO_PF_INVALID))
return kvm_mmu_page_fault(vcpu, gpa, 0, NULL, 0);
if (unlikely(ret == RET_MMIO_PF_RETRY))
return 1;

3
arch/x86/kvm/x86.c
View File

@ -7084,8 +7084,7 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
* If memory slot is created, or moved, we need to clear all
* mmio sptes.
*/
if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE))
kvm_mmu_zap_mmio_sptes(kvm);
kvm_mmu_invalidate_mmio_sptes(kvm);
}
void kvm_arch_flush_shadow_all(struct kvm *kvm)