On 06/25/2010 03:06 PM, Xiao Guangrong wrote:
Consider using small page to fit guest's large page mapping: If the mapping is writable but the dirty flag is not set, we will find the read-only direct sp and setup the mapping, then if the write #PF occur, we will mark this mapping writable in the read-only direct sp, now, other real read-only mapping will happily write it without #PF. It may hurt guest's COW Fixed by re-install the mapping when write #PF occur. Signed-off-by: Xiao Guangrong<xiaoguangrong@xxxxxxxxxxxxxx> --- arch/x86/kvm/mmu.c | 3 ++- arch/x86/kvm/paging_tmpl.h | 18 ++++++++++++++++++ 2 files changed, 20 insertions(+), 1 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 556a798..0412ba4 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -153,7 +153,8 @@ module_param(oos_shadow, bool, 0644); #define CREATE_TRACE_POINTS #include "mmutrace.h" -#define SPTE_HOST_WRITEABLE (1ULL<< PT_FIRST_AVAIL_BITS_SHIFT) +#define SPTE_HOST_WRITEABLE (1ULL<< PT_FIRST_AVAIL_BITS_SHIFT) +#define SPTE_NO_DIRTY (2ULL<< PT_FIRST_AVAIL_BITS_SHIFT) #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level) diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index e46eb8a..fdba751 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -325,6 +325,20 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, break; } + if (*sptep& SPTE_NO_DIRTY) { + struct kvm_mmu_page *child; + + WARN_ON(level != gw->level); + WARN_ON(!is_shadow_present_pte(*sptep)); + if (dirty) { + child = page_header(*sptep& + PT64_BASE_ADDR_MASK); + mmu_page_remove_parent_pte(child, sptep); + __set_spte(sptep, shadow_trap_nonpresent_pte); + kvm_flush_remote_tlbs(vcpu->kvm); + } + } +
Instead of adding a new bit, can you encode the protection in the direct sp's access bits? So we'll have one sp for read-only or writeable-but-not-dirty small pages, and another sp for writeable-and-dirty small pages.
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