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Commit be38d276 authored by Avi Kivity's avatar Avi Kivity
Browse files

KVM: MMU: Introduce drop_spte() 



When we call rmap_remove(), we (almost) always immediately follow it by
an __set_spte() to a nonpresent pte.  Since we need to perform the two
operations atomically, to avoid losing the dirty and accessed bits, introduce
a helper drop_spte() and convert all call sites.

The operation is still nonatomic at this point.

Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent dd180b3e

arch/x86/kvm/mmu.c

+17 −13
Original line number Diff line number Diff line
@@ -658,6 +658,12 @@ static void rmap_remove(struct kvm *kvm, u64 *spte) 
	}

}



static void drop_spte(struct kvm *kvm, u64 *sptep, u64 new_spte)

{

	rmap_remove(kvm, sptep);

	__set_spte(sptep, new_spte);

}



static u64 *rmap_next(struct kvm *kvm, unsigned long *rmapp, u64 *spte)

{

	struct kvm_rmap_desc *desc;
@@ -722,9 +728,9 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn) 
			BUG_ON((*spte & (PT_PAGE_SIZE_MASK|PT_PRESENT_MASK)) != (PT_PAGE_SIZE_MASK|PT_PRESENT_MASK));

			pgprintk("rmap_write_protect(large): spte %p %llx %lld\n", spte, *spte, gfn);

			if (is_writable_pte(*spte)) {

				rmap_remove(kvm, spte);

				drop_spte(kvm, spte,

					  shadow_trap_nonpresent_pte);

				--kvm->stat.lpages;

				__set_spte(spte, shadow_trap_nonpresent_pte);

				spte = NULL;

				write_protected = 1;

			}
@@ -744,8 +750,7 @@ static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp, 
	while ((spte = rmap_next(kvm, rmapp, NULL))) {

		BUG_ON(!(*spte & PT_PRESENT_MASK));

		rmap_printk("kvm_rmap_unmap_hva: spte %p %llx\n", spte, *spte);

		rmap_remove(kvm, spte);

		__set_spte(spte, shadow_trap_nonpresent_pte);

		drop_spte(kvm, spte, shadow_trap_nonpresent_pte);

		need_tlb_flush = 1;

	}

	return need_tlb_flush;
@@ -767,8 +772,7 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp, 
		rmap_printk("kvm_set_pte_rmapp: spte %p %llx\n", spte, *spte);

		need_flush = 1;

		if (pte_write(*ptep)) {

			rmap_remove(kvm, spte);

			__set_spte(spte, shadow_trap_nonpresent_pte);

			drop_spte(kvm, spte, shadow_trap_nonpresent_pte);

			spte = rmap_next(kvm, rmapp, NULL);

		} else {

			new_spte = *spte &~ (PT64_BASE_ADDR_MASK);
@@ -1464,7 +1468,8 @@ static void kvm_mmu_page_unlink_children(struct kvm *kvm, 
			} else {

				if (is_large_pte(ent))

					--kvm->stat.lpages;

				rmap_remove(kvm, &pt[i]);

				drop_spte(kvm, &pt[i],

					  shadow_trap_nonpresent_pte);

			}

		}

		pt[i] = shadow_trap_nonpresent_pte;
@@ -1868,9 +1873,8 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, 
		if (level > PT_PAGE_TABLE_LEVEL &&

		    has_wrprotected_page(vcpu->kvm, gfn, level)) {

			ret = 1;

			rmap_remove(vcpu->kvm, sptep);

			spte = shadow_trap_nonpresent_pte;

			goto set_pte;

			drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte);

			goto done;

		}



		spte |= PT_WRITABLE_MASK;
@@ -1902,6 +1906,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, 


set_pte:

	__set_spte(sptep, spte);

done:

	return ret;

}
@@ -1938,8 +1943,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, 
		} else if (pfn != spte_to_pfn(*sptep)) {

			pgprintk("hfn old %lx new %lx\n",

				 spte_to_pfn(*sptep), pfn);

			rmap_remove(vcpu->kvm, sptep);

			__set_spte(sptep, shadow_trap_nonpresent_pte);

			drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte);

			kvm_flush_remote_tlbs(vcpu->kvm);

		} else

			was_rmapped = 1;
@@ -2591,7 +2595,7 @@ static void mmu_pte_write_zap_pte(struct kvm_vcpu *vcpu, 
	pte = *spte;

	if (is_shadow_present_pte(pte)) {

		if (is_last_spte(pte, sp->role.level))

			rmap_remove(vcpu->kvm, spte);

			drop_spte(vcpu->kvm, spte, shadow_trap_nonpresent_pte);

		else {

			child = page_header(pte & PT64_BASE_ADDR_MASK);

			mmu_page_remove_parent_pte(child, spte);

arch/x86/kvm/paging_tmpl.h

+6 −7
Original line number Diff line number Diff line
@@ -353,8 +353,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, 
		}



		if (is_large_pte(*sptep)) {

			rmap_remove(vcpu->kvm, sptep);

			__set_spte(sptep, shadow_trap_nonpresent_pte);

			drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte);

			kvm_flush_remote_tlbs(vcpu->kvm);

		}
@@ -516,11 +515,12 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva) 
			pte_gpa += (sptep - sp->spt) * sizeof(pt_element_t);



			if (is_shadow_present_pte(*sptep)) {

				rmap_remove(vcpu->kvm, sptep);

				if (is_large_pte(*sptep))

					--vcpu->kvm->stat.lpages;

				drop_spte(vcpu->kvm, sptep,

					  shadow_trap_nonpresent_pte);

				need_flush = 1;

			}

			} else

				__set_spte(sptep, shadow_trap_nonpresent_pte);

			break;

		}
@@ -637,12 +637,11 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, 
		      !is_present_gpte(gpte) || !(gpte & PT_ACCESSED_MASK)) {

			u64 nonpresent;



			rmap_remove(vcpu->kvm, &sp->spt[i]);

			if (is_present_gpte(gpte) || !clear_unsync)

				nonpresent = shadow_trap_nonpresent_pte;

			else

				nonpresent = shadow_notrap_nonpresent_pte;

			__set_spte(&sp->spt[i], nonpresent);

			drop_spte(vcpu->kvm, &sp->spt[i], nonpresent);

			continue;

		}