On Mon, Nov 05, 2012 at 08:10:08PM +0800, Xiao Guangrong wrote:
> In order to detecting spte remapping, we can simply check whether the
> spte has already been pointing to the pfn even if the spte is not the
> last spte for middle spte is pointing to the kernel pfn which can not
> be mapped to userspace
>
> Also, update slot and stat.lpages iff the spte is not remapped
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 40 +++++++++++++---------------------------
> 1 files changed, 13 insertions(+), 27 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 692ebb1..4ea731e 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2420,8 +2420,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> pfn_t pfn, bool speculative,
> bool host_writable)
> {
> - int was_rmapped = 0;
> - int rmap_count;
> + bool was_rmapped = false;
>
> pgprintk("%s: spte %llx access %x write_fault %d"
> " user_fault %d gfn %llx\n",
> @@ -2429,25 +2428,13 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
> write_fault, user_fault, gfn);
>
> if (is_rmap_spte(*sptep)) {
> - /*
> - * If we overwrite a PTE page pointer with a 2MB PMD, unlink
> - * the parent of the now unreachable PTE.
> - */
> - if (level > PT_PAGE_TABLE_LEVEL &&
> - !is_large_pte(*sptep)) {
> - struct kvm_mmu_page *child;
> - u64 pte = *sptep;
> + if (pfn != spte_to_pfn(*sptep)) {
> + struct kvm_mmu_page *sp = page_header(__pa(sptep));
>
> - child = page_header(pte & PT64_BASE_ADDR_MASK);
> - drop_parent_pte(child, sptep);
> - kvm_flush_remote_tlbs(vcpu->kvm);
How come its safe to drop this case?
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