Commit 5ce4786f authored by Junaid Shahid's avatar Junaid Shahid Committed by Paolo Bonzini
Browse files

kvm: x86: Make sync_page() flush remote TLBs once only 



sync_page() calls set_spte() from a loop across a page table. It would
work better if set_spte() left the TLB flushing to its callers, so that
sync_page() can aggregate into a single call.

Signed-off-by: default avatarJunaid Shahid <junaids@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 42522d08

arch/x86/kvm/mmu.c

+12 −4
Original line number Diff line number Diff line
@@ -2724,6 +2724,10 @@ static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) 
	return true;

}



/* Bits which may be returned by set_spte() */

#define SET_SPTE_WRITE_PROTECTED_PT	BIT(0)

#define SET_SPTE_NEED_REMOTE_TLB_FLUSH	BIT(1)



static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,

		    unsigned pte_access, int level,

		    gfn_t gfn, kvm_pfn_t pfn, bool speculative,
@@ -2800,7 +2804,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, 
		if (mmu_need_write_protect(vcpu, gfn, can_unsync)) {

			pgprintk("%s: found shadow page for %llx, marking ro\n",

				 __func__, gfn);

			ret = 1;

			ret |= SET_SPTE_WRITE_PROTECTED_PT;

			pte_access &= ~ACC_WRITE_MASK;

			spte &= ~(PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE);

		}
@@ -2816,7 +2820,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, 


set_pte:

	if (mmu_spte_update(sptep, spte))

		kvm_flush_remote_tlbs(vcpu->kvm);

		ret |= SET_SPTE_NEED_REMOTE_TLB_FLUSH;

done:

	return ret;

}
@@ -2827,6 +2831,7 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access, 
{

	int was_rmapped = 0;

	int rmap_count;

	int set_spte_ret;

	int ret = RET_PF_RETRY;



	pgprintk("%s: spte %llx write_fault %d gfn %llx\n", __func__,
@@ -2854,12 +2859,15 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access, 
			was_rmapped = 1;

	}



	if (set_spte(vcpu, sptep, pte_access, level, gfn, pfn, speculative,

	      true, host_writable)) {

	set_spte_ret = set_spte(vcpu, sptep, pte_access, level, gfn, pfn,

				speculative, true, host_writable);

	if (set_spte_ret & SET_SPTE_WRITE_PROTECTED_PT) {

		if (write_fault)

			ret = RET_PF_EMULATE;

		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);

	}

	if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH)

		kvm_flush_remote_tlbs(vcpu->kvm);



	if (unlikely(is_mmio_spte(*sptep)))

		ret = RET_PF_EMULATE;

arch/x86/kvm/paging_tmpl.h

+8 −4
Original line number Diff line number Diff line
@@ -968,6 +968,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 
	int i, nr_present = 0;

	bool host_writable;

	gpa_t first_pte_gpa;

	int set_spte_ret = 0;



	/* direct kvm_mmu_page can not be unsync. */

	BUG_ON(sp->role.direct);
@@ -1024,12 +1025,15 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 


		host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE;



		set_spte(vcpu, &sp->spt[i], pte_access,

			 PT_PAGE_TABLE_LEVEL, gfn,

			 spte_to_pfn(sp->spt[i]), true, false,

			 host_writable);

		set_spte_ret |= set_spte(vcpu, &sp->spt[i],

					 pte_access, PT_PAGE_TABLE_LEVEL,

					 gfn, spte_to_pfn(sp->spt[i]),

					 true, false, host_writable);

	}



	if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH)

		kvm_flush_remote_tlbs(vcpu->kvm);



	return nr_present;

}

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