diff options
| author | Avi Kivity <avi@redhat.com> | 2012-09-16 15:03:02 +0300 |
|---|---|---|
| committer | Avi Kivity <avi@redhat.com> | 2012-09-20 13:00:09 +0300 |
| commit | b514c30f7729b66af481fde3c1225e832e339d5b (patch) | |
| tree | 8d0744aa7f2fd57fd31e9aed72de177b74d7900d /arch/x86/kvm | |
| parent | 71331a1da1e3a66d14bb3864f99e32d84ab5a76f (diff) | |
KVM: MMU: Avoid access/dirty update loop if all is well
Keep track of accessed/dirty bits; if they are all set, do not
enter the accessed/dirty update loop.
Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/paging_tmpl.h | 26 |
1 files changed, 20 insertions, 6 deletions
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 95a64d1dccc..810c1da2ee4 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -151,7 +151,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker, pt_element_t pte; pt_element_t __user *uninitialized_var(ptep_user); gfn_t table_gfn; - unsigned index, pt_access, pte_access; + unsigned index, pt_access, pte_access, accessed_dirty, shift; gpa_t pte_gpa; int offset; const int write_fault = access & PFERR_WRITE_MASK; @@ -180,6 +180,7 @@ retry_walk: ASSERT((!is_long_mode(vcpu) && is_pae(vcpu)) || (mmu->get_cr3(vcpu) & CR3_NONPAE_RESERVED_BITS) == 0); + accessed_dirty = PT_ACCESSED_MASK; pt_access = pte_access = ACC_ALL; ++walker->level; @@ -224,6 +225,7 @@ retry_walk: goto error; } + accessed_dirty &= pte; pte_access = pt_access & gpte_access(vcpu, pte); walker->ptes[walker->level - 1] = pte; @@ -251,11 +253,23 @@ retry_walk: if (!write_fault) protect_clean_gpte(&pte_access, pte); - ret = FNAME(update_accessed_dirty_bits)(vcpu, mmu, walker, write_fault); - if (unlikely(ret < 0)) - goto error; - else if (ret) - goto retry_walk; + /* + * On a write fault, fold the dirty bit into accessed_dirty by shifting it one + * place right. + * + * On a read fault, do nothing. + */ + shift = write_fault >> ilog2(PFERR_WRITE_MASK); + shift *= PT_DIRTY_SHIFT - PT_ACCESSED_SHIFT; + accessed_dirty &= pte >> shift; + + if (unlikely(!accessed_dirty)) { + ret = FNAME(update_accessed_dirty_bits)(vcpu, mmu, walker, write_fault); + if (unlikely(ret < 0)) + goto error; + else if (ret) + goto retry_walk; + } walker->pt_access = pt_access; walker->pte_access = pte_access; |