linux-kernel - Re: [PATCHv5 23/30] x86/boot: Avoid #VE during boot for TDX platforms

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Date:   Tue, 8 Mar 2022 09:19:06 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...el.com, luto@...nel.org, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
        joro@...tes.org, jpoimboe@...hat.com, knsathya@...nel.org,
        pbonzini@...hat.com, sdeep@...are.com, seanjc@...gle.com,
        tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
        thomas.lendacky@....com, brijesh.singh@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv5 23/30] x86/boot: Avoid #VE during boot for TDX platforms

On 3/8/2022 6:33 AM, Kirill A. Shutemov wrote:
> On Mon, Mar 07, 2022 at 05:29:27PM +0800, Xiaoyao Li wrote:
...
>> Even though CPUID reports MCE is supported, all the access to MCE related
>> MSRs causes #VE. If they are accessed via mce_rdmsrl(), the #VE will be
>> fixed up and goes to ex_handler_msr_mce(). Finally lead to panic().
> 
> It is not panic, but warning. Like this:
> 
> 	unchecked MSR access error: RDMSR from 0x179 at rIP: 0xffffffff810df1e9 (__mcheck_cpu_cap_init+0x9/0x130)
> 	Call Trace:
> 	 <TASK>
> 	 mcheck_cpu_init+0x3d/0x2c0
> 	 identify_cpu+0x85a/0x910
> 	 identify_boot_cpu+0xc/0x98
> 	 check_bugs+0x6/0xa7
> 	 start_kernel+0x363/0x3d1
> 	 secondary_startup_64_no_verify+0xe5/0xeb
> 	 </TASK>
> 
> It is annoying, but not fatal. The patchset is big enough as it is.
> I tried to keep patch number under control.
> 

I did hit panic as below.

[    0.578792] mce: MSR access error: RDMSR from 0x475 at rIP: 
0xffffffffb94daa92 (mce_rdmsrl+0x22/0x60)
[    0.578792] Call Trace:
[    0.578792]  <TASK>
[    0.578792]  machine_check_poll+0xf0/0x260
[    0.578792]  __mcheck_cpu_init_generic+0x3d/0xb0
[    0.578792]  mcheck_cpu_init+0x16b/0x4a0
[    0.578792]  identify_cpu+0x467/0x5c0
[    0.578792]  identify_boot_cpu+0x10/0x9a
[    0.578792]  check_bugs+0x2a/0xa06
[    0.578792]  start_kernel+0x6bc/0x6f1
[    0.578792]  x86_64_start_reservations+0x24/0x26
[    0.578792]  x86_64_start_kernel+0xad/0xb2
[    0.578792]  secondary_startup_64_no_verify+0xe4/0xeb
[    0.578792]  </TASK>
[    0.578792] Kernel panic - not syncing: MCA architectural violation!
[    0.578792] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 
5.17.0-rc5-td-guest-upstream+ #2
[    0.578792] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 
0.0.0 02/06/2015
[    0.578792] Call Trace:
[    0.578792]  <TASK>
[    0.578792]  dump_stack_lvl+0x49/0x5f
[    0.578792]  dump_stack+0x10/0x12
[    0.578792]  panic+0xf9/0x2d0
[    0.578792]  ex_handler_msr_mce+0x5e/0x5e
[    0.578792]  fixup_exception+0x2f4/0x310
[    0.578792]  exc_virtualization_exception+0x9b/0x100
[    0.578792]  asm_exc_virtualization_exception+0x12/0x40
[    0.578792] RIP: 0010:mce_rdmsrl+0x22/0x60
[    0.578792] Code: a0 b9 e8 75 4d fb ff 90 55 48 89 e5 41 54 53 89 fb 
48 c7 c7 9c c1 f6 b9 e8 4b 28 00 00 65 8a 05 97 52 b4 46 84 c0 75 10 89 
d9 <0f> 32 48 c1 e2 20 48 09 d0 5b 41 5c 5d c3 89 df e8 c9 5a 17 ff 4c
[    0.578792] RSP: 0000:ffffffffba203cd8 EFLAGS: 00010246
[    0.578792] RAX: 0000000000000000 RBX: 0000000000000475 RCX: 
0000000000000475
[    0.578792] RDX: 00000000000001d0 RSI: ffffffffb9f6c19c RDI: 
ffffffffb9ece016
[    0.578792] RBP: ffffffffba203ce8 R08: ffffffffba203cb0 R09: 
ffffffffba203cb4
[    0.578792] R10: 0000000000000000 R11: 000000000000000f R12: 
0000000000000001
[    0.578792] R13: ffffffffba203dc0 R14: 000000000000000a R15: 
000000000000001d
[    0.578792]  ? mce_rdmsrl+0x15/0x60
[    0.578792]  machine_check_poll+0xf0/0x260
[    0.578792]  __mcheck_cpu_init_generic+0x3d/0xb0
[    0.578792]  mcheck_cpu_init+0x16b/0x4a0
[    0.578792]  identify_cpu+0x467/0x5c0
[    0.578792]  identify_boot_cpu+0x10/0x9a
[    0.578792]  check_bugs+0x2a/0xa06
[    0.578792]  start_kernel+0x6bc/0x6f1
[    0.578792]  x86_64_start_reservations+0x24/0x26
[    0.578792]  x86_64_start_kernel+0xad/0xb2
[    0.578792]  secondary_startup_64_no_verify+0xe4/0xeb
[    0.578792]  </TASK>
[    0.578792] ---[ end Kernel panic - not syncing: MCA architectural 
violation! ]---