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From: Xiao Guangrong on 3 Jul 2010 04:10
Commit 341d9b535b6c simplify reload logic while entry guest mode, it
can avoid unnecessary sync-root if KVM_REQ_MMU_RELOAD and
KVM_REQ_MMU_SYNC both set.

But, it cause a issue that when we handle 'KVM_REQ_TLB_FLUSH', the
root is invalid, it is triggered during my test:

Kernel BUG at ffffffffa00212b8 [verbose debug info unavailable]
.......

[<ffffffff810f5caf>] ? fget_light+0x111/0x28e
[<ffffffff81103963>] sys_ioctl+0x47/0x6a
[<ffffffff81002c1b>] system_call_fastpath+0x16/0x1b
Code: f0 eb 21 f7 c2 00 00 00 04 74 22 48 8d 45 f0 48 c7 45 f0 00 00 00 00 48 c7 45 f8 00 00 00 00 b9 02 00 00 00 66 0f 38 80 08 77 02 <0f> 0b c9 c3 55 48 89 e5 0f 1f 44 00 00 ba 00 68 00 00 48 8b 8f
RIP [<ffffffffa00212b8>] vmx_flush_tlb+0xdf/0xe3 [kvm_intel]
RSP <ffff8800be269ca8>

Fixed by directly return if the root is not ready.

Signed-off-by: Xiao Guangrong <xiaoguangrong(a)cn.fujitsu.com>
---
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/mmu.c | 2 --
arch/x86/kvm/vmx.c | 5 ++++-
3 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 2bda624..8f522ec 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -40,6 +40,8 @@
0xFFFFFF0000000000ULL)

#define INVALID_PAGE (~(hpa_t)0)
+#define VALID_PAGE(x) ((x) != INVALID_PAGE)
+
#define UNMAPPED_GVA (~(gpa_t)0)

/* KVM Hugepage definitions for x86 */
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index a0c5c31..399ddb0 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -92,8 +92,6 @@ module_param(oos_shadow, bool, 0644);
#define PT_FIRST_AVAIL_BITS_SHIFT 9
#define PT64_SECOND_AVAIL_BITS_SHIFT 52

-#define VALID_PAGE(x) ((x) != INVALID_PAGE)
-
#define PT64_LEVEL_BITS 9

#define PT64_LEVEL_SHIFT(level) \
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 806ab12..ebaaeaf 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1831,8 +1831,11 @@ static void exit_lmode(struct kvm_vcpu *vcpu)
static void vmx_flush_tlb(struct kvm_vcpu *vcpu)
{
vpid_sync_context(to_vmx(vcpu));
- if (enable_ept)
+ if (enable_ept) {
+ if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
+ return;
ept_sync_context(construct_eptp(vcpu->arch.mmu.root_hpa));
+ }
}

static void vmx_decache_cr0_guest_bits(struct kvm_vcpu *vcpu)
--
1.6.1.2

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