Re: [PATCH v2 3/10] KVM: MMU: fix direct sp's access corruptted

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 06/25/2010 03:06 PM, Xiao Guangrong wrote:
Consider using small page to fit guest's large page mapping:

If the mapping is writable but the dirty flag is not set, we will find
the read-only direct sp and setup the mapping, then if the write #PF
occur, we will mark this mapping writable in the read-only direct sp,
now, other real read-only mapping will happily write it without #PF.

It may hurt guest's COW

Fixed by re-install the mapping when write #PF occur.

Signed-off-by: Xiao Guangrong<xiaoguangrong@xxxxxxxxxxxxxx>
---
  arch/x86/kvm/mmu.c         |    3 ++-
  arch/x86/kvm/paging_tmpl.h |   18 ++++++++++++++++++
  2 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 556a798..0412ba4 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -153,7 +153,8 @@ module_param(oos_shadow, 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_NO_DIRTY		(2ULL<<  PT_FIRST_AVAIL_BITS_SHIFT)

  #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index e46eb8a..fdba751 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -325,6 +325,20 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
  			break;
  		}

+		if (*sptep&  SPTE_NO_DIRTY) {
+			struct kvm_mmu_page *child;
+
+			WARN_ON(level !=  gw->level);
+			WARN_ON(!is_shadow_present_pte(*sptep));
+			if (dirty) {
+				child = page_header(*sptep&
+						      PT64_BASE_ADDR_MASK);
+				mmu_page_remove_parent_pte(child, sptep);
+				__set_spte(sptep, shadow_trap_nonpresent_pte);
+				kvm_flush_remote_tlbs(vcpu->kvm);
+			}
+		}
+

Instead of adding a new bit, can you encode the protection in the direct sp's access bits? So we'll have one sp for read-only or writeable-but-not-dirty small pages, and another sp for writeable-and-dirty small pages.

--
error compiling committee.c: too many arguments to function

--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux