On 12/27/2010 12:35 PM, Takuya Yoshikawa wrote:
On Mon, 27 Dec 2010 12:08:45 +0200
Avi Kivity<avi@xxxxxxxxxx> wrote:
> Instead, drop large mappings, which were the reason we dropped shadow.
>
> Signed-off-by: Avi Kivity<avi@xxxxxxxxxx>
> ---
>
> v2: maintain largepage stats
>
> arch/x86/kvm/mmu.c | 12 ++++++++----
> virt/kvm/kvm_main.c | 7 +------
> 2 files changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 43bd5e3..dc36088 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3444,14 +3444,18 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot)
> if (!test_bit(slot, sp->slot_bitmap))
> continue;
>
> - if (sp->role.level != PT_PAGE_TABLE_LEVEL)
> - continue;
> -
> pt = sp->spt;
> - for (i = 0; i< PT64_ENT_PER_PAGE; ++i)
> + for (i = 0; i< PT64_ENT_PER_PAGE; ++i) {
> + if (sp->role.level != PT_PAGE_TABLE_LEVEL
> + && is_large_pte(pt[i])) {
> + drop_spte(kvm,&pt[i],
> + shadow_trap_nonpresent_pte);
> + --kvm->stat.lpages;
> + }
> /* avoid RMW */
> if (is_writable_pte(pt[i]))
> update_spte(&pt[i], pt[i]& ~PT_WRITABLE_MASK);
I'm a bit confused here.
rmap_write_protect() does drop_spte() but update_spte() in
/* check for huge page mappings */ loop.
rmap_write_protect() protects a 4k page, so it uses update_spte() to
drop the W bit, and drops large mappings that point to the same 4k
page. We can't drop the W bit from the large page, because that will
write protect 511 unrelated pages.
I may be able to learn something from your share code later on.
Unlikely - I was thinking of sharing the
+ drop_spte(kvm,&pt[i],
+ shadow_trap_nonpresent_pte);
+ --kvm->stat.lpages;
bits. Now I'm thinking of dropping kvm->stat, I think we have all the
information it provides covered by tracepoints.
--
error compiling committee.c: too many arguments to function
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