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authorXiao Guangrong <guangrong.xiao@linux.intel.com>2015-08-05 12:04:19 +0800
committerSasha Levin <sasha.levin@oracle.com>2015-10-27 22:14:46 -0400
commit2c333eb66bca69bfadf5ae3424a3fb32037b5d48 (patch)
tree8a8101dd46e7fa69ed7db8f73f6bd9c32b9ccb11
parentc22fac8485a145a8e8b2634839c7a33bc334d16b (diff)
downloadlinux-linaro-stable-2c333eb66bca69bfadf5ae3424a3fb32037b5d48.tar.gz
KVM: MMU: fix validation of mmio page fault
[ Upstream commit 6f691251c0350ac52a007c54bf3ef62e9d8cdc5e ] We got the bug that qemu complained with "KVM: unknown exit, hardware reason 31" and KVM shown these info: [84245.284948] EPT: Misconfiguration. [84245.285056] EPT: GPA: 0xfeda848 [84245.285154] ept_misconfig_inspect_spte: spte 0x5eaef50107 level 4 [84245.285344] ept_misconfig_inspect_spte: spte 0x5f5fadc107 level 3 [84245.285532] ept_misconfig_inspect_spte: spte 0x5141d18107 level 2 [84245.285723] ept_misconfig_inspect_spte: spte 0x52e40dad77 level 1 This is because we got a mmio #PF and the handler see the mmio spte becomes normal (points to the ram page) However, this is valid after introducing fast mmio spte invalidation which increases the generation-number instead of zapping mmio sptes, a example is as follows: 1. QEMU drops mmio region by adding a new memslot 2. invalidate all mmio sptes 3. VCPU 0 VCPU 1 access the invalid mmio spte access the region originally was MMIO before set the spte to the normal ram map mmio #PF check the spte and see it becomes normal ram mapping !!! This patch fixes the bug just by dropping the check in mmio handler, it's good for backport. Full check will be introduced in later patches Reported-by: Pavel Shirshov <ru.pchel@gmail.com> Tested-by: Pavel Shirshov <ru.pchel@gmail.com> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
-rw-r--r--arch/x86/kvm/mmu.c45
1 files changed, 0 insertions, 45 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f696dedb0fa7..23875c26fb34 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -372,12 +372,6 @@ static u64 __get_spte_lockless(u64 *sptep)
{
return ACCESS_ONCE(*sptep);
}
-
-static bool __check_direct_spte_mmio_pf(u64 spte)
-{
- /* It is valid if the spte is zapped. */
- return spte == 0ull;
-}
#else
union split_spte {
struct {
@@ -493,23 +487,6 @@ retry:
return spte.spte;
}
-
-static bool __check_direct_spte_mmio_pf(u64 spte)
-{
- union split_spte sspte = (union split_spte)spte;
- u32 high_mmio_mask = shadow_mmio_mask >> 32;
-
- /* It is valid if the spte is zapped. */
- if (spte == 0ull)
- return true;
-
- /* It is valid if the spte is being zapped. */
- if (sspte.spte_low == 0ull &&
- (sspte.spte_high & high_mmio_mask) == high_mmio_mask)
- return true;
-
- return false;
-}
#endif
static bool spte_is_locklessly_modifiable(u64 spte)
@@ -3230,21 +3207,6 @@ static bool quickly_check_mmio_pf(struct kvm_vcpu *vcpu, u64 addr, bool direct)
return vcpu_match_mmio_gva(vcpu, addr);
}
-
-/*
- * On direct hosts, the last spte is only allows two states
- * for mmio page fault:
- * - It is the mmio spte
- * - It is zapped or it is being zapped.
- *
- * This function completely checks the spte when the last spte
- * is not the mmio spte.
- */
-static bool check_direct_spte_mmio_pf(u64 spte)
-{
- return __check_direct_spte_mmio_pf(spte);
-}
-
static u64 walk_shadow_page_get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr)
{
struct kvm_shadow_walk_iterator iterator;
@@ -3287,13 +3249,6 @@ int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct)
}
/*
- * It's ok if the gva is remapped by other cpus on shadow guest,
- * it's a BUG if the gfn is not a mmio page.
- */
- if (direct && !check_direct_spte_mmio_pf(spte))
- return RET_MMIO_PF_BUG;
-
- /*
* If the page table is zapped by other cpus, let CPU fault again on
* the address.
*/