On Fri, Dec 16, 2011 at 06:13:42PM +0800, Xiao Guangrong wrote:
> unsync is only used for the page of level == 1 and unsync_children is only
> used in the upper page, so combine them to reduce the size of shadow page
> structure
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
> ---
> Documentation/virtual/kvm/mmu.txt | 5 ++-
> arch/x86/include/asm/kvm_host.h | 14 +++++++++++-
> arch/x86/kvm/mmu.c | 39 +++++++++++++++++++++++++-----------
> arch/x86/kvm/mmu_audit.c | 6 ++--
> arch/x86/kvm/mmutrace.h | 3 +-
> arch/x86/kvm/paging_tmpl.h | 2 +-
> 6 files changed, 48 insertions(+), 21 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt
> index 5dc972c..4a5fedd 100644
> --- a/Documentation/virtual/kvm/mmu.txt
> +++ b/Documentation/virtual/kvm/mmu.txt
> @@ -205,14 +205,15 @@ Shadow pages contain the following information:
> this page's spt. Otherwise, parent_ptes points at a data structure
> with a list of parent_ptes.
> unsync:
> + It is used when role.level == 1, only level 1 shadow pages can be unsync.
> If true, then the translations in this page may not match the guest's
> translation. This is equivalent to the state of the tlb when a pte is
> changed but before the tlb entry is flushed. Accordingly, unsync ptes
> are synchronized when the guest executes invlpg or flushes its tlb by
> other means. Valid for leaf pages.
> unsync_children:
> - How many sptes in the page point at pages that are unsync (or have
> - unsynchronized children).
> + It is used when role.level > 1 and indicates how many sptes in the page
> + point at unsync pages or unsynchronized children.
> unsync_child_bitmap:
> A bitmap indicating which sptes in spt point (directly or indirectly) at
> pages that may be unsynchronized. Used to quickly locate all unsychronized
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 52d6640..c0a89cd 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -233,9 +233,19 @@ struct kvm_mmu_page {
> * in this shadow page.
> */
> DECLARE_BITMAP(slot_bitmap, KVM_MEM_SLOTS_NUM);
> - bool unsync;
> int root_count; /* Currently serving as active root */
> - unsigned int unsync_children;
> +
> + /*
> + * If role.level == 1, unsync indicates whether the sp is
> + * unsync, otherwise unsync_children indicates the number
> + * of sptes which point at unsync sp or unsychronized children.
> + * See sp_is_unsync() / sp_unsync_children_num.
> + */
> + union {
> + bool unsync;
> + unsigned int unsync_children;
> + };
> +
> unsigned long parent_ptes; /* Reverse mapping for parent_pte */
> DECLARE_BITMAP(unsync_child_bitmap, 512);
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 2a2a9b4..6913a16 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -151,6 +151,21 @@ module_param(dbg, bool, 0644);
>
> #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
>
> +static bool sp_is_unsync(struct kvm_mmu_page *sp)
> +{
> + return sp->role.level == PT_PAGE_TABLE_LEVEL && sp->unsync;
> +}
> +
> +static unsigned int sp_unsync_children_num(struct kvm_mmu_page *sp)
> +{
> + unsigned int num = 0;
> +
> + if (sp->role.level != PT_PAGE_TABLE_LEVEL)
> + num = sp->unsync_children;
> +
> + return num;
> +}
IIRC there are windows where unsync_children is not accurate. Have you
verified this function is not called inside one of those windows?
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