From: Changbin Du <[email protected]>
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 <[email protected]>
---
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
2017-09-05 18:37+0800, [email protected]:
> From: Changbin Du <[email protected]>
>
> 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 <[email protected]>
> ---
> 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.
On Wed, Sep 13, 2017 at 04:39:56PM +0200, Radim Krčmář wrote:
> 2017-09-05 18:37+0800, [email protected]:
> > From: Changbin Du <[email protected]>
> >
> > 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 <[email protected]>
> > ---
> > 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?
>
hmm, a recent Paolo's cleanup patch already fixed it.
e08d26f ("KVM: x86: simplify ept_misconfig")
In the past, PFERR_RSVD_MASK is not set.
So this patch doesnt need any more. thanks.
> Thanks.
--
Thanks,
Changbin Du