From 0d551bb698e1328f685ae3611c4a4a96f41bef97 Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Thu, 31 May 2007 15:23:35 +0300 Subject: KVM: Make shadow pte updates atomic With guest smp, a second vcpu might see partial updates when the first vcpu services a page fault. So delay all updates until we have figured out what the pte should look like. Note that on i386, this is still not completely atomic as a 64-bit write will be split into two on a 32-bit machine. Signed-off-by: Avi Kivity --- drivers/kvm/paging_tmpl.h | 37 ++++++++++++++++++++----------------- 1 file changed, 20 insertions(+), 17 deletions(-) diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h index 35f264f346d..397a4039eaa 100644 --- a/drivers/kvm/paging_tmpl.h +++ b/drivers/kvm/paging_tmpl.h @@ -205,11 +205,12 @@ static void FNAME(set_pte_common)(struct kvm_vcpu *vcpu, { hpa_t paddr; int dirty = *gpte & PT_DIRTY_MASK; - int was_rmapped = is_rmap_pte(*shadow_pte); + u64 spte = *shadow_pte; + int was_rmapped = is_rmap_pte(spte); pgprintk("%s: spte %llx gpte %llx access %llx write_fault %d" " user_fault %d gfn %lx\n", - __FUNCTION__, *shadow_pte, (u64)*gpte, access_bits, + __FUNCTION__, spte, (u64)*gpte, access_bits, write_fault, user_fault, gfn); if (write_fault && !dirty) { @@ -218,34 +219,35 @@ static void FNAME(set_pte_common)(struct kvm_vcpu *vcpu, FNAME(mark_pagetable_dirty)(vcpu->kvm, walker); } - *shadow_pte |= *gpte & PT_PTE_COPY_MASK; - *shadow_pte |= access_bits << PT_SHADOW_BITS_OFFSET; + spte |= *gpte & PT_PTE_COPY_MASK; + spte |= access_bits << PT_SHADOW_BITS_OFFSET; if (!dirty) access_bits &= ~PT_WRITABLE_MASK; paddr = gpa_to_hpa(vcpu, gaddr & PT64_BASE_ADDR_MASK); - *shadow_pte |= PT_PRESENT_MASK; + spte |= PT_PRESENT_MASK; if (access_bits & PT_USER_MASK) - *shadow_pte |= PT_USER_MASK; + spte |= PT_USER_MASK; if (is_error_hpa(paddr)) { - *shadow_pte |= gaddr; - *shadow_pte |= PT_SHADOW_IO_MARK; - *shadow_pte &= ~PT_PRESENT_MASK; + spte |= gaddr; + spte |= PT_SHADOW_IO_MARK; + spte &= ~PT_PRESENT_MASK; + *shadow_pte = spte; return; } - *shadow_pte |= paddr; + spte |= paddr; - if (!write_fault && (*shadow_pte & PT_SHADOW_USER_MASK) && - !(*shadow_pte & PT_USER_MASK)) { + if (!write_fault && (spte & PT_SHADOW_USER_MASK) && + !(spte & PT_USER_MASK)) { /* * If supervisor write protect is disabled, we shadow kernel * pages as user pages so we can trap the write access. */ - *shadow_pte |= PT_USER_MASK; - *shadow_pte &= ~PT_WRITABLE_MASK; + spte |= PT_USER_MASK; + spte &= ~PT_WRITABLE_MASK; access_bits &= ~PT_WRITABLE_MASK; } @@ -253,7 +255,7 @@ static void FNAME(set_pte_common)(struct kvm_vcpu *vcpu, || (write_fault && !is_write_protection(vcpu) && !user_fault)) { struct kvm_mmu_page *shadow; - *shadow_pte |= PT_WRITABLE_MASK; + spte |= PT_WRITABLE_MASK; if (user_fault) { mmu_unshadow(vcpu, gfn); goto unshadowed; @@ -264,8 +266,8 @@ static void FNAME(set_pte_common)(struct kvm_vcpu *vcpu, pgprintk("%s: found shadow page for %lx, marking ro\n", __FUNCTION__, gfn); access_bits &= ~PT_WRITABLE_MASK; - if (is_writeble_pte(*shadow_pte)) { - *shadow_pte &= ~PT_WRITABLE_MASK; + if (is_writeble_pte(spte)) { + spte &= ~PT_WRITABLE_MASK; kvm_arch_ops->tlb_flush(vcpu); } if (write_fault) @@ -278,6 +280,7 @@ unshadowed: if (access_bits & PT_WRITABLE_MASK) mark_page_dirty(vcpu->kvm, gaddr >> PAGE_SHIFT); + *shadow_pte = spte; page_header_update_slot(vcpu->kvm, shadow_pte, gaddr); if (!was_rmapped) rmap_add(vcpu, shadow_pte); -- cgit v1.2.3