Commit f8f55942 authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Gleb Natapov
Browse files

KVM: MMU: fast invalidate all mmio sptes 



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: default avatarXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Reviewed-by: default avatarGleb Natapov <gleb@redhat.com>
Reviewed-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent b37fbea6

arch/x86/include/asm/kvm_host.h

+1 −1
Original line number Diff line number Diff line
@@ -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);

arch/x86/kvm/mmu.c

+46 −8
Original line number Diff line number Diff line
@@ -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;

arch/x86/kvm/mmu.h

+4 −1
Original line number Diff line number Diff line
@@ -57,11 +57,14 @@ 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.

 * 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

};

arch/x86/kvm/paging_tmpl.h

+5 −2
Original line number Diff line number Diff line
@@ -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)

arch/x86/kvm/vmx.c

+4 −0
Original line number Diff line number Diff line
@@ -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;

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