Re: [PATCH] KVM: x86: fix bogus warning about reserved bits

[Borislav Petkov <bp@alien8.de>]

On Tue, Sep 22, 2015 at 11:04:38PM +0200, Paolo Bonzini wrote:
> Let's add more debugging output:

Here you go:

[   50.474002] walk_shadow_page_get_mmio_spte: detect reserved bits on spte, addr 0xb8000 (level 4, 0xf0000000000f8)
[   50.484249] walk_shadow_page_get_mmio_spte: detect reserved bits on spte, addr 0xb8000 (level 3, 0xf000000000078)
[   50.494492] walk_shadow_page_get_mmio_spte: detect reserved bits on spte, addr 0xb8000 (level 2, 0xf000000000078)
[   50.504767] dump hierarchy:
[   50.507595] ------ spte 0x416533027 level 4.
[   50.507595] ------ spte 0x416534027 level 3.
[   50.507596] ------ spte 0x416535027 level 2.
[   50.507596] ------ spte 0xffff0000000b8f67 level 1.
[   50.507597] ------------[ cut here ]------------
[   50.507616] WARNING: CPU: 4 PID: 3539 at arch/x86/kvm/mmu.c:3396 handle_mmio_page_fault.part.57+0x1a/0x20 [kvm]()
[   50.507630] Modules linked in: tun sha256_ssse3 sha256_generic drbg binfmt_misc ipv6 vfat fat fuse dm_crypt dm_mod kvm_amd kvm crc32_pclmul aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd amd64_edac_mod k10temp edac_core fam15h_power amdkfd amd_iommu_v2 radeon acpi_cpufreq
[   50.507632] CPU: 4 PID: 3539 Comm: qemu-system-x86 Not tainted 4.3.0-rc2+ #2
[   50.507633] Hardware name: To be filled by O.E.M. To be filled by O.E.M./M5A97 EVO R2.0, BIOS 1503 01/16/2013
[   50.507635]  ffffffffa0433932 ffff880416973b78 ffffffff812c758a 0000000000000000
[   50.507637]  ffff880416973bb0 ffffffff810534c1 ffff8804231c0000 000000000000000f
[   50.507638]  00000000000b8000 0000000000000000 00000000ffffffff ffff880416973bc0
[   50.507639] Call Trace:
[   50.507643]  [<ffffffff812c758a>] dump_stack+0x4e/0x84
[   50.507646]  [<ffffffff810534c1>] warn_slowpath_common+0x91/0xd0
[   50.507647]  [<ffffffff810535ba>] warn_slowpath_null+0x1a/0x20
[   50.507657]  [<ffffffffa0405aba>] handle_mmio_page_fault.part.57+0x1a/0x20 [kvm]
[   50.507667]  [<ffffffffa040d3d0>] tdp_page_fault+0x2a0/0x2b0 [kvm]
[   50.507673]  [<ffffffff810a282d>] ? __lock_acquire+0x57d/0x17a0
[   50.507682]  [<ffffffffa0407615>] kvm_mmu_page_fault+0x35/0x240 [kvm]
[   50.507685]  [<ffffffffa068d6b8>] pf_interception+0x108/0x1d0 [kvm_amd]
[   50.507688]  [<ffffffffa068fd10>] handle_exit+0x150/0xa40 [kvm_amd]
[   50.507697]  [<ffffffffa03fe398>] ? kvm_arch_vcpu_ioctl_run+0x4c8/0x16f0 [kvm]
[   50.507706]  [<ffffffffa03fe403>] kvm_arch_vcpu_ioctl_run+0x533/0x16f0 [kvm]
[   50.507715]  [<ffffffffa03fe398>] ? kvm_arch_vcpu_ioctl_run+0x4c8/0x16f0 [kvm]
[   50.507717]  [<ffffffff816bd852>] ? mutex_lock_killable_nested+0x312/0x480
[   50.507724]  [<ffffffffa03e5979>] ? kvm_vcpu_ioctl+0x79/0x6f0 [kvm]
[   50.507726]  [<ffffffff8107e133>] ? preempt_count_sub+0xb3/0x110
[   50.507733]  [<ffffffffa03e5c3f>] kvm_vcpu_ioctl+0x33f/0x6f0 [kvm]
[   50.507735]  [<ffffffff811939d7>] do_vfs_ioctl+0x2d7/0x530
[   50.507737]  [<ffffffff8119f889>] ? __fget_light+0x29/0x90
[   50.507738]  [<ffffffff81193c7c>] SyS_ioctl+0x4c/0x90
[   50.507740]  [<ffffffff816c1a9b>] entry_SYSCALL_64_fastpath+0x16/0x73
[   50.507741] ---[ end trace ff23795fcc279cbd ]---

> Thus same as before.
> 
> Just to be safe, can you try using "-cpu host" on the QEMU command
> line and see if it changes anything?  This would catch things such
> as an Intel CPUID on an AMD host.

Here's my full qemu command:

qemu-system-x86_64 -enable-kvm -gdb tcp::1234 -cpu host -m 2048 -hda /home/boris/kvm/debian/sid-x86_64.img -hdb /home/boris/kvm/swap.img -boot menu=off,order=c -localtime -net nic,model=rtl8139 -net user,hostfwd=tcp::1235-:22 -usbdevice tablet -kernel /home/boris/kernel/linux-2.6/arch/x86/boot/bzImage -append "root=/dev/sda1 resume=/dev/sdb1 debug ignore_loglevel log_buf_len=16M earlyprintk=ttyS0,115200 console=ttyS0,115200 console=tty0 " -monitor pty -virtfs local,path=/tmp,mount_tag=tmp,security_model=none -serial file:/home/boris/kvm/test-x86_64-1235.log -snapshot -name "Debian x86_64:1235" -smp 8

and that splats too:

[  146.891735] walk_shadow_page_get_mmio_spte: detect reserved bits on spte, addr 0xb8000 (level 4, 0xf0000000000f8)
[  146.901981] walk_shadow_page_get_mmio_spte: detect reserved bits on spte, addr 0xb8000 (level 3, 0xf000000000078)
[  146.912224] walk_shadow_page_get_mmio_spte: detect reserved bits on spte, addr 0xb8000 (level 2, 0xf000000000078)
[  146.922496] dump hierarchy:
[  146.925331] ------ spte 0x37d47027 level 4.
[  146.925332] ------ spte 0x37d46027 level 3.
[  146.925332] ------ spte 0xb9faa027 level 2.
[  146.925333] ------ spte 0xffff0000000b8f67 level 1.
[  146.925333] ------------[ cut here ]------------
[  146.925351] WARNING: CPU: 6 PID: 3753 at arch/x86/kvm/mmu.c:3396 handle_mmio_page_fault.part.57+0x1a/0x20 [kvm]()
[  146.925371] Modules linked in: tun sha256_ssse3 sha256_generic drbg binfmt_misc ipv6 vfat fat fuse dm_crypt dm_mod kvm_amd kvm crc32_pclmul aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd amd64_edac_mod k10temp edac_core fam15h_power amdkfd amd_iommu_v2 radeon acpi_cpufreq
[  146.925373] CPU: 6 PID: 3753 Comm: qemu-system-x86 Tainted: G        W       4.3.0-rc2+ #2
[  146.925374] Hardware name: To be filled by O.E.M. To be filled by O.E.M./M5A97 EVO R2.0, BIOS 1503 01/16/2013
[  146.925376]  ffffffffa0433932 ffff880423377b78 ffffffff812c758a 0000000000000000
[  146.925378]  ffff880423377bb0 ffffffff810534c1 ffff88042315bf00 000000000000000f
[  146.925379]  00000000000b8000 0000000000000000 00000000ffffffff ffff880423377bc0
[  146.925380] Call Trace:
[  146.925384]  [<ffffffff812c758a>] dump_stack+0x4e/0x84
[  146.925386]  [<ffffffff810534c1>] warn_slowpath_common+0x91/0xd0
[  146.925388]  [<ffffffff810535ba>] warn_slowpath_null+0x1a/0x20
[  146.925397]  [<ffffffffa0405aba>] handle_mmio_page_fault.part.57+0x1a/0x20 [kvm]
[  146.925408]  [<ffffffffa040d3d0>] tdp_page_fault+0x2a0/0x2b0 [kvm]
[  146.925410]  [<ffffffff810a282d>] ? __lock_acquire+0x57d/0x17a0
[  146.925420]  [<ffffffffa0407615>] kvm_mmu_page_fault+0x35/0x240 [kvm]
[  146.925423]  [<ffffffffa068d6b8>] pf_interception+0x108/0x1d0 [kvm_amd]
[  146.925431]  [<ffffffffa068fd10>] handle_exit+0x150/0xa40 [kvm_amd]
[  146.925440]  [<ffffffffa03fe398>] ? kvm_arch_vcpu_ioctl_run+0x4c8/0x16f0 [kvm]
[  146.925449]  [<ffffffffa03fe403>] kvm_arch_vcpu_ioctl_run+0x533/0x16f0 [kvm]
[  146.925458]  [<ffffffffa03fe398>] ? kvm_arch_vcpu_ioctl_run+0x4c8/0x16f0 [kvm]
[  146.925461]  [<ffffffff816bd852>] ? mutex_lock_killable_nested+0x312/0x480
[  146.925467]  [<ffffffffa03e5979>] ? kvm_vcpu_ioctl+0x79/0x6f0 [kvm]
[  146.925469]  [<ffffffff8107e133>] ? preempt_count_sub+0xb3/0x110
[  146.925476]  [<ffffffffa03e5c3f>] kvm_vcpu_ioctl+0x33f/0x6f0 [kvm]
[  146.925478]  [<ffffffff811939d7>] do_vfs_ioctl+0x2d7/0x530
[  146.925480]  [<ffffffff8119f889>] ? __fget_light+0x29/0x90
[  146.925481]  [<ffffffff81193c7c>] SyS_ioctl+0x4c/0x90
[  146.925482]  [<ffffffff816c1a9b>] entry_SYSCALL_64_fastpath+0x16/0x73
[  146.925484] ---[ end trace ff23795fcc279cbe ]---

Thanks.

-- 
Regards/Gruss,
    Boris.

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