2017-09-05 18:37+0800, changbin.du@xxxxxxxxx: > 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; Hm, handle_ept_misconfig() calls kvm_mmu_page_fault with error_code = PFERR_RSVD_MASK. This error_code gets propagated and checked at the beginning of page_fault_can_be_fast(), where it should break the function execution. How did the execution get all the way to the loop? Thanks.
