Re: [PATCH] arm/arm64: KVM: Fix set_clear_sgi_pend_reg offset

Christoffer Dall
2014-09-30T11:41:35Z

On Tue, Sep 30, 2014 at 09:48:02AM +0800, Shannon Zhao wrote:
> Hi Christoffer,
>
> On 2014/9/26 21:44, Christoffer Dall wrote:
> > On Fri, Sep 26, 2014 at 12:16:35PM +0200, Christoffer Dall wrote:
> >> On Fri, Sep 26, 2014 at 05:26:00PM +0800, Shannon Zhao wrote:
> >>>
> >>>
> >>> On 2014/9/26 16:44, Christoffer Dall wrote:
> >>>> Hi Shannon,
> >>>>
> >>>> On Fri, Sep 26, 2014 at 01:57:46PM +0800, Shannon Zhao wrote:
> >>>>>
> >>>>> On 2014/9/26 1:49, Christoffer Dall wrote:
> >>>>>> The sgi values calculated in read_set_clear_sgi_pend_reg() and
> >>>>>> write_set_clear_sgi_pend_reg() were horribly incorrectly multiplied by 4
> >>>>>> with catastrophic results in that subfunctions ended up overwriting
> >>>>>> memory not allocated for the expected purpose.
> >>>>>>
> >>>>>> This showed up as bugs in kfree() and the kernel complaining a lot of
> >>>>>> you turn on memory debugging.
> >>>>>>
> >>>>>> This addresses: http://marc.info/?l=kvm&m=141164910007868&w=2
> >>>>>>
> >>>>>> Reported-by: Shannon Zhao <zhaoshenglong@huawei.com>
> >>>>>> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> >>>>>> ---
> >>>>>> virt/kvm/arm/vgic.c | 4 ++--
> >>>>>> 1 file changed, 2 insertions(+), 2 deletions(-)
> >>>>>>
> >>>>>> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> >>>>>> index b6fab0f..8629678 100644
> >>>>>> --- a/virt/kvm/arm/vgic.c
> >>>>>> +++ b/virt/kvm/arm/vgic.c
> >>>>>> @@ -816,7 +816,7 @@ static bool read_set_clear_sgi_pend_reg(struct kvm_vcpu *vcpu,
> >>>>>> {
> >>>>>> struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> >>>>>> int sgi;
> >>>>>> - int min_sgi = (offset & ~0x3) * 4;
> >>>>>> + int min_sgi = (offset & ~0x3);
> >>>>>> int max_sgi = min_sgi + 3;
> >>>>>> int vcpu_id = vcpu->vcpu_id;
> >>>>>> u32 reg = 0;
> >>>>>> @@ -837,7 +837,7 @@ static bool write_set_clear_sgi_pend_reg(struct kvm_vcpu *vcpu,
> >>>>>> {
> >>>>>> struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> >>>>>> int sgi;
> >>>>>> - int min_sgi = (offset & ~0x3) * 4;
> >>>>>> + int min_sgi = (offset & ~0x3);
> >>>>>> int max_sgi = min_sgi + 3;
> >>>>>> int vcpu_id = vcpu->vcpu_id;
> >>>>>> u32 reg;
> >>>>>>
> >>>>> Hi Christoffer,
> >>>>>
> >>>>> I have test this patch for a few hours. The kfree() bug doesn't appear again.
> >>>>> But I come to another problem as followed.
> >>>>> The test is that start 2 VMs, sleep 10 and do pkill qemu.
> >>>>>
> >>>>> qemu-system-aar[1207]: unhandled level 1 permission fault (11) at 0xffffc01ed6c200, esr 0x9200000d
> >>>>> pgd = ffffffc012986000
> >>>>> [ffffc01ed6c200] *pgd=0000000000000000, *pud=0000000000000000
> >>>>>
> >>>>> CPU: 1 PID: 1207 Comm: qemu-system-aar Not tainted 3.17.0-rc4+ #1
> >>>>> task: ffffffc87b072900 ti: ffffffc0129e0000 task.ti: ffffffc0129e0000
> >>>>> PC is at 0x4181a0
> >>>>> LR is at 0x41826c
> >>>>> pc : [<00000000004181a0>] lr : [<000000000041826c>] pstate: 80000000
> >>>>> sp : 0000007fcd38ace0
> >>>>> x29: 0000007fcd38ace0 x28: 0000000000000000
> >>>>> x27: 0000000000000000 x26: 0000000000000000
> >>>>> x25: 0000000000000000 x24: 0000000000000000
> >>>>> x23: 0000000000000000 x22: 0000000000000000
> >>>>> x21: 0000000000000000 x20: 0000000000000000
> >>>>> x19: 0000007fcd38b070 x18: 0000007fcd38ab10
> >>>>> x17: 0000007f9bb14480 x16: 00000000009f2370
> >>>>> x15: ffffffffffffffff x14: 0000000000000000
> >>>>> x13: 0000000000000000 x12: 0000000000000268
> >>>>> x11: 00000000115e5520 x10: 0101010101010101
> >>>>> x9 : 0000000000000004 x8 : 0000000000ac7a78
> >>>>> x7 : 0000000000000000 x6 : 000000000000003f
> >>>>> x5 : 0000000000000040 x4 : 0000000000000000
> >>>>> x3 : 0000000000000030 x2 : 0000000000000001
> >>>>> x1 : ffffffc01ed6c200 x0 : ffffffc01ed6c200
> >>>>>
> >>>> Hmmm, I just ran a similar loop with a number of tests in the VM for a
> >>>> few hours and I didn't see this error.
> >>> Yeah, it really need to run longer.
> >>> After running about one hour this problem first appears and after running
> >>> about 4 hours it second appears.
> >>>>
> >>>> In any case, this patch should still be merged, but we should try to
> >>>> reproduce your setup.
> >>> Your patch really solves the kfree() bug. I'll add tested-by line.
> >>>>
> >>>> What is your command line, exact QEMU version, the file system you use,
> >>>> and the guest kernel you are running?
> >>> My test script is as followed. QEMU version is v2.1.0 release.
> >>> The fs is linaro-image-lamp-genericarmv8-20140727-701.rootfs.tar.gz.
> >>> Host kernel is based on marc's branch "kvmtool-vgic-dyn" with your patch
> >>> "Fix set_clear_sgi_pend_reg offset".
> >>> Guest kernel is 3.16 release.
> >>>
> >>> while true
> >>> do
> >>> qemu-system-aarch64 \
> >>> -enable-kvm -smp 4 \
> >>> -kernel Image \
> >>> -m 512 -machine virt,kernel_irqchip=on \
> >>> -initrd guestfs.cpio.gz \
> >>> -cpu host \
> >>> -chardev pty,id=pty0,mux=on -monitor chardev:pty0 \
> >>> -serial chardev:pty0 -daemonize \
> >>> -vnc 0.0.0.0:0 \
> >>> -append "rdinit=/sbin/init console=ttyAMA0 mem=512M root=/dev/ram earlyprintk=pl011,0x9000000 rw" &
> >>>
> >>> qemu-system-aarch64 \
> >>> -enable-kvm -smp 4 \
> >>> -kernel Image \
> >>> -m 512 -machine virt,kernel_irqchip=on \
> >>> -initrd guestfs.cpio.gz \
> >>> -cpu host \
> >>> -chardev pty,id=pty0,mux=on -monitor chardev:pty0 \
> >>> -serial chardev:pty0 -daemonize \
> >>> -vnc 0.0.0.0:1 \
> >>> -append "rdinit=/sbin/init console=ttyAMA0 mem=512M root=/dev/ram earlyprintk=pl011,0x9000000 rw" &
> >>> sleep 5
> >>> pkill qemu
> >>
> >> ok, I'll try to reproduce.
> >>
> > With kvmarm/queue as both host and guest and otherwise not using vnc but
> > nographic and a serial output, I've now been running this for 5 hours
> > straight without any issues. That's 1131 runs (2x number of guests
> > booted) and counting without seeing this...
> >
> I have ran the test with kvmarm/queue as both host and guest using
> nographic and a serial output. The problem appears.
> My environment info:
> kvmarm/queue:
> commit f003101732065c7e61a4d5394cfc69b01b0bb157
> arm/arm64: KVM: Fix VTTBR_BADDR_MASK and pgd alloc
> qemu:
> commit 541bbb07eb197a870661ed702ae1f15c7d46aea6
> Update version for v2.1.0 release
> fs:
> guest: linaro-image-minimal-genericarmv8-20140727-701.rootfs.tar.gz
> host: use above minimal fs and add some libs from linaro-image-lamp-genericarmv8-20140727-701.rootfs.tar.gz
>
> Once this problem appeared, it appears every time when start a vm.
> The problem info is always same:
> qemu-system-aar[1207]: unhandled level 1 permission fault (11) at 0xffffc01ed6c200, esr 0x9200000d

I can't reproduce on my system I'm afraid. I'm running on APM XGene
with a Ubuntu distro and a defconfig of the kernel, using the same
versions of the kernel and qemu as you are.

Which hardware platform are you using?

In any case, this doesn't appear to be a KVM bug if it's user distro
dependent.

-Christoffer