On Tue, May 29, 2012 at 02:49:14PM +0800, Xiao Guangrong wrote:
> This bit indicates whether the spte can be writable on MMU, that means
> the corresponding gpte is writable and the corresponding gfn is not
> protected by shadow page protection
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 41 +++++++++++++++++++++++++++--------------
> 1 files changed, 27 insertions(+), 14 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 4810992..150c5ad 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -145,7 +145,8 @@ module_param(dbg, 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_MMU_WRITEABLE (1ULL << (PT_FIRST_AVAIL_BITS_SHIFT + 1))
>
> #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
>
> @@ -1065,32 +1066,43 @@ static void drop_spte(struct kvm *kvm, u64 *sptep)
> rmap_remove(kvm, sptep);
> }
>
> +static bool spte_can_be_writable(u64 spte)
> +{
> + return !(~spte & (SPTE_HOST_WRITEABLE | SPTE_MMU_WRITEABLE));
> +}
> +
> /* Return true if the spte is dropped. */
> -static bool spte_write_protect(struct kvm *kvm, u64 *sptep, bool *flush)
> +static bool
> +spte_write_protect(struct kvm *kvm, u64 *sptep, bool *flush, bool pt_protect)
> {
> u64 spte = *sptep;
>
> - if (!is_writable_pte(spte))
> + if (!is_writable_pte(spte) &&
> + !(pt_protect && spte_can_be_writable(spte)))
> return false;
>
> rmap_printk("rmap_write_protect: spte %p %llx\n", sptep, *sptep);
>
> - *flush |= true;
> if (is_large_pte(spte)) {
> WARN_ON(page_header(__pa(sptep))->role.level ==
> PT_PAGE_TABLE_LEVEL);
> +
> + *flush |= true;
> drop_spte(kvm, sptep);
> --kvm->stat.lpages;
> return true;
> }
>
> + if (pt_protect)
> + spte &= ~SPTE_MMU_WRITEABLE;
> spte = spte & ~PT_WRITABLE_MASK;
> - mmu_spte_update(sptep, spte);
> +
> + *flush = mmu_spte_update(sptep, spte);
This clears previous flush value when looping over multiple sptes in
a single rmapp.
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