Re: kvm: GPF in native_write_cr4

[Haozhong Zhang]

Hi Wanpeng,

On 10/31/17 19:10 +0800, Wanpeng Li wrote:
> 2017-10-31 17:59 GMT+08:00 Dmitry Vyukov <dvyukov@xxxxxxxxxx>:
> > Hello,
> >
> > I am seeing the following crash on upstream
> > 15f859ae5c43c7f0a064ed92d33f7a5bc5de6de0 (Oct 26).
> > Reproducer:
> > https://gist.githubusercontent.com/dvyukov/a9690f90c39c1e3b1b6c7acda2d5ef89/raw/33e07f3d6779005fc475764e0802e4a5aee8d0cf/gistfile1.txt
> > I run qemu with -append "kvm-intel.nested=1" -enable-kvm -cpu host. My
> > host cpu is E5-2690.
> >
> 
> I can't reproduce this w/ latest kvm/queue in both L0 and L1. In
> addition, there is a commit tries to fix cr4 recently.
> https://git.kernel.org/pub/scm/virt/kvm/kvm.git/commit/?id=8eb3f87d903168bdbd1222776a6b1e281f50513e

The calltrace in this bug report is the same as what I got before
above commit.

In the previous bug, L0 KVM misused L2 CR4 as L1 CR4. When L1 KVM
tried to clear L1 CR4.VMXE in L1 VM shutdown path, L0 KVM considered
L1 intended to clear/set other bits as well (because of the wrong L2
CR4 was used by L0 KVM as L1 CR4), but changes to extra bits may not
be allowed against other L1 states.

In my previous fix, I tried to fix one place of such L1/L2 CR4
misuse. If there is no other places of CR4 misuse, you may have a look
at the guest states checked by kvm_set_cr4() against guest CR4
changes, and check whether L1 and L2 versions of any of them are
misused.

It would make the debug easier if we can log which check fails in
kvm_set_cr4() when the calltrace appears (e.g., by adding printk
before return 1 in kvm_set_cr4()).


Haozhong



>  The testcast is complex, if the below strace log is as you expected?
> 
> execve("./a.out", ["./a.out"], [/* 32 vars */]) = 0
> uname({sysname="Linux", nodename="kernel", ...}) = 0
> brk(NULL)                               = 0x1d42000
> brk(0x1d431c0)                          = 0x1d431c0
> arch_prctl(ARCH_SET_FS, 0x1d42880)      = 0
> readlink("/proc/self/exe", "/home/kernel/a.out", 4096) = 18
> brk(0x1d641c0)                          = 0x1d641c0
> brk(0x1d65000)                          = 0x1d65000
> access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
> mmap(0x20000000, 11481088, PROT_READ|PROT_WRITE,
> MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x20000000
> openat(AT_FDCWD, "/dev/kvm", O_WRONLY)  = 3
> ioctl(3, KVM_CREATE_VM or LOGGER_GET_LOG_BUF_SIZE, 0) = 4
> ioctl(4, KVM_CREATE_VCPU, 0)            = 5
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1230) = 0
> ioctl(4, KVM_SET_USER_MEMORY_REGION, 0x7fff5e6c1170) = 0
> ioctl(5, KVM_GET_SREGS, 0x7fff5e6c1330) = 0
> open("/dev/kvm", O_RDWR)                = 6
> ioctl(6, KVM_GET_SUPPORTED_CPUID, 0x7fff5e6c1470) = 0
> ioctl(5, KVM_SET_CPUID2, 0x7fff5e6c1470) = 0
> close(6)                                = 0
> ioctl(5, KVM_SET_MSRS, 0x7fff5e6c0c30)  = 5
> ioctl(5, KVM_SET_SREGS, 0x7fff5e6c1330) = 0
> ioctl(5, KVM_SET_REGS, 0x7fff5e6c1230)  = 0
> mremap(0x20998000, 4096, 16384, MREMAP_MAYMOVE|MREMAP_FIXED,
> 0x200fa000) = 0x200fa000
> ioctl(5, KVM_RUN, 0)                    = 0
> mbind(0x20000000, 8192, MPOL_DEFAULT 0x20001ff8, 2, MPOL_MF_MOVE) = 0
> exit_group(0)                           = ?
> +++ exited with 0 +++
> i
> 
> Regards,
> Wanpeng Li
> 
> > general protection fault: 0000 [#1] SMP KASAN
> > Modules linked in:
> > CPU: 1 PID: 3064 Comm: a.out Not tainted 4.14.0-rc6+ #11
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> > task: ffff880064c203c0 task.stack: ffff880066718000
> > RIP: 0010:native_write_cr4+0x4/0x10 arch/x86/include/asm/special_insns.h:75
> > RSP: 0018:ffff88006671f598 EFLAGS: 00010097
> > RAX: ffff880064c203c0 RBX: 00000000001606e0 RCX: 0000000000000000
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000001606e0
> > RBP: ffff88006671f598 R08: 0000000000000006 R09: 0000000000000006
> > R10: ffff880064c203c0 R11: 0000000000000000 R12: 0000000000000001
> > R13: ffff88006ca94828 R14: ffff88006ca94850 R15: ffff88006ca80000
> > FS:  00000000019cd880(0000) GS:ffff88006ca80000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000000000000 CR3: 0000000005a22001 CR4: 00000000001626e0
> > Call Trace:
> >  __write_cr4 arch/x86/include/asm/paravirt.h:76 [inline]
> >  cr4_clear_bits arch/x86/include/asm/tlbflush.h:197 [inline]
> >  kvm_cpu_vmxoff arch/x86/kvm/vmx.c:3571 [inline]
> >  hardware_disable+0x197/0x210 arch/x86/kvm/vmx.c:3577
> >  kvm_arch_hardware_disable+0x35/0xd0 arch/x86/kvm/x86.c:7920
> >  hardware_disable_nolock+0x30/0x40
> > arch/x86/kvm/../../../virt/kvm/kvm_main.c:3282
> >  on_each_cpu+0xca/0x1b0 kernel/smp.c:604
> >  hardware_disable_all_nolock+0x44/0x60
> > arch/x86/kvm/../../../virt/kvm/kvm_main.c:3300
> >  hardware_disable_all arch/x86/kvm/../../../virt/kvm/kvm_main.c:3306 [inline]
> >  kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:735 [inline]
> >  kvm_put_kvm+0x887/0xe00 arch/x86/kvm/../../../virt/kvm/kvm_main.c:748
> >  kvm_vm_release+0x42/0x50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:759
> >  __fput+0x301/0x7e0 fs/file_table.c:210
> >  ____fput+0x15/0x20 fs/file_table.c:244
> >  task_work_run+0x19e/0x250 kernel/task_work.c:112
> >  exit_task_work include/linux/task_work.h:21 [inline]
> >  do_exit+0x99f/0x18b0 kernel/exit.c:865
> >  do_group_exit+0x14b/0x3f0 kernel/exit.c:968
> >  SYSC_exit_group kernel/exit.c:979 [inline]
> >  SyS_exit_group+0x1d/0x20 kernel/exit.c:977
> >  entry_SYSCALL_64_fastpath+0x1f/0xbe
> > RIP: 0033:0x443849
> > RSP: 002b:00007ffe58a95c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000443849
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> > RBP: 0000000000000086 R08: 000000000000003c R09: 00000000000000e7
> > R10: ffffffffffffffc0 R11: 0000000000000246 R12: 0000000000000000
> > R13: 0000000000404800 R14: 0000000000404890 R15: 0000000000000000
> > Code: 0f 1f 80 00 00 00 00 55 48 89 e5 0f 20 d8 5d c3 0f 1f 80 00 00
> > 00 00 55 48 89 e5 0f 22 df 5d c3 0f 1f 80 00 00 00 00 55 48 89 e5 <0f>
> > 22 e7 5d c3 0f 1f 80 00 00 00 00 55 48 89 e5 44 0f 20 c0 5d
> > RIP: native_write_cr4+0x4/0x10 arch/x86/include/asm/special_insns.h:75
> > RSP: ffff88006671f598
> > ---[ end trace 6f9dbcc14aa47936 ]---