[RESEND][PATCH] kvm: x86: Do not handle MMIO request in fast_page_fault

[changbin . du]

From: Changbin Du <changbin.du@xxxxxxxxx>

If it is a MMIO request, it should be handled by slow path. This patch
actually fixed below warning when mmu debug is enabled.

WARNING: CPU: 5 PID: 2282 at arch/x86/kvm/mmu.c:226 fast_page_fault+0x41b/0x520
CPU: 5 PID: 2282 Comm: qemu-system-x86 Not tainted 4.13.0-rc6+ #34
task: ffff9b47f5286000 task.stack: ffffb18d03b28000
RIP: 0010:fast_page_fault+0x41b/0x520
Call Trace:
  tdp_page_fault+0xfb/0x290
  kvm_mmu_page_fault+0x61/0x120
  handle_ept_misconfig+0x1ba/0x1c0
  vmx_handle_exit+0xb8/0xd70
  ? kvm_arch_vcpu_ioctl_run+0x9b6/0x18e0
  kvm_arch_vcpu_ioctl_run+0xa5a/0x18e0
  ? kvm_arch_vcpu_load+0x62/0x230
  kvm_vcpu_ioctl+0x340/0x6c0
  ? kvm_vcpu_ioctl+0x340/0x6c0
  ? lock_acquire+0xf5/0x1f0
  do_vfs_ioctl+0xa2/0x670
  ? __fget+0x107/0x200
  SyS_ioctl+0x79/0x90
  entry_SYSCALL_64_fastpath+0x23/0xc2

Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx>
---
 arch/x86/kvm/mmu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 9d3f275..63c3360 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3180,6 +3180,9 @@ static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level,
 			    iterator.level < level)
 				break;
 
+		if (is_mmio_spte(spte))
+			break;
+
 		sp = page_header(__pa(iterator.sptep));
 		if (!is_last_spte(spte, sp->role.level))
 			break;
-- 
2.7.4