| Message ID | 1382534973-13197-4-git-send-email-xiaoguangrong@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Oct 23, 2013 at 09:29:21PM +0800, Xiao Guangrong wrote: > Relax the tlb flush condition since we will write-protect the spte out of mmu > lock. Note lockless write-protection only marks the writable spte to readonly > and the spte can be writable only if both SPTE_HOST_WRITEABLE and > SPTE_MMU_WRITEABLE are set (that are tested by spte_is_locklessly_modifiable) > > This patch is used to avoid this kind of race: > > VCPU 0 VCPU 1 > lockless wirte protection: > set spte.w = 0 > lock mmu-lock > > write protection the spte to sync shadow page, > see spte.w = 0, then without flush tlb > > unlock mmu-lock > > !!! At this point, the shadow page can still be > writable due to the corrupt tlb entry > Flush all TLB > > Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 8739208..62f18ec 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -595,7 +595,8 @@ static bool mmu_spte_update(u64 *sptep, u64 new_spte) * we always atomicly update it, see the comments in * spte_has_volatile_bits(). */ - if (is_writable_pte(old_spte) && !is_writable_pte(new_spte)) + if (spte_is_locklessly_modifiable(old_spte) && + !is_writable_pte(new_spte)) ret = true; if (!shadow_accessed_mask)
Relax the tlb flush condition since we will write-protect the spte out of mmu lock. Note lockless write-protection only marks the writable spte to readonly and the spte can be writable only if both SPTE_HOST_WRITEABLE and SPTE_MMU_WRITEABLE are set (that are tested by spte_is_locklessly_modifiable) This patch is used to avoid this kind of race: VCPU 0 VCPU 1 lockless wirte protection: set spte.w = 0 lock mmu-lock write protection the spte to sync shadow page, see spte.w = 0, then without flush tlb unlock mmu-lock !!! At this point, the shadow page can still be writable due to the corrupt tlb entry Flush all TLB Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> --- arch/x86/kvm/mmu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)