Re: [PATCH v2] i386: Add the support for AMD EPYC 3rd generation processors

[Babu Moger]

Pankaj, Sure.

I will add signoff from you if it is fine with you.

Signed-off-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>

Let me know.
Thanks
Babu

On 3/2/21 12:38 PM, Pankaj Gupta wrote:
> Hi Babu,
> 
> I confirm I can see both the ssbd & irbs features in guest with the
> below patch. There was some issue at my end, Sorry! for the confusion.
> Can you please post the official patch for inclusion.
> 
> Best regards,
> Pankaj
> 
> On Mon, Mar 1, 2021 at 9:38 PM Babu Moger <babu.moger@amd.com> wrote:
>>
>>
>>
>>> -----Original Message-----
>>> From: Pankaj Gupta <pankaj.gupta@cloud.ionos.com>
>>> Sent: Monday, March 1, 2021 2:22 PM
>>> To: Moger, Babu <Babu.Moger@amd.com>
>>> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>; Paolo Bonzini
>>> <pbonzini@redhat.com>; richard.henderson@linaro.org; Eduardo Habkost
>>> <ehabkost@redhat.com>; Qemu Developers <qemu-devel@nongnu.org>
>>> Subject: Re: [PATCH v2] i386: Add the support for AMD EPYC 3rd generation
>>> processors
>>>
>>>>> Hi Babu,
>>>>>
>>>>> I tried to test below patch for AMD EPYC Rome CPU and I got below error
>>> [1]:
>>>>>
>>>>> Also, I noticed SSBD CPU flag for guest was still available even
>>>>> without this patch, I noticed that for the guest, AMD_SSBD not got set.
>>>>>
>>>>> Guest:
>>>>> 0x80000008 0x00: eax=0x00003028 ebx=0x00009205 ecx=0x00002003
>>>>> edx=0x00000000
>>>>>
>>>>> [1]
>>>>> [    0.008000] unchecked MSR access error: WRMSR to 0x48 (tried to
>>>>> write 0x0000000000000000) at rIP: 0xffffffff9245c9e4
>>>>> (native_write_msr+0x4/0x20)
>>>>> [    0.008000]  [<ffffffff9243a6c5>] ? x86_spec_ctrl_setup_ap+0x35/0x50
>>>>> [    0.008000]  [<ffffffff92439423>] ? identify_secondary_cpu+0x53/0x80
>>>>> [    0.008000]  [<ffffffff9244adfa>] ? start_secondary+0x6a/0x1b0
>>>>>
>>>>> 0.011970] unchecked MSR access error: RDMSR from 0x48 at rIP:
>>>>> 0xffffffff9245c772 (native_read_msr+0x2/0x40)
>>>>
>>>> I did not see any problem with these patches.
>>>> My guest setup.
>>>> # lscpu |grep -o ssbd
>>>> ssbd
>>>> [root@rome-vm ~]# uname -r
>>>> 4.18.0-147.el8.x86_64
>>>> [root@rome-vm ~]# cat /etc/redhat-release Red Hat Enterprise Linux
>>>> release 8.1 (Ootpa) # wrmsr 0x48 7 [root@rome-vm ~]# rdmsr 0x48
>>>> 7
>>>>
>>>>
>>>> My host os.
>>>> # uname -r
>>>> 4.18.0-193.el8.x86_64
>>>> [root@rome images]# cat /etc/redhat-release Red Hat Enterprise Linux
>>>> release 8.2 Beta (Ootpa)
>>>>
>>>> Also, I only see ssbd feature when add this patch(EPYC-Rome-v2).
>>>> Otherwise, I don’t see ssbd feature.
>>>
>>> Thanks for checking!
>>> Can you also see the ibrs feature inside guest with this patch?
>>
>> Yes, The feature is available with this patch. Otherwise it is not available.
>> [root@rome-vm ~]# lscpu |grep -o ibrs
>> ibrs
>>
>>>
>>> Thanks,
>>> Pankaj
>>>>
>>>> Thanks
>>>> Babu
>>>>
>>>>
>>>>>
>>>>> Thanks,
>>>>> Pankaj
>>>>>
>>>>>>> It is normally added as v2 for compatibility. Like this.
>>>>>>
>>>>>> o.k. Thanks!
>>>>>> I will test this tomorrow.
>>>>>>
>>>>>>>
>>>>>>> diff --git a/target/i386/cpu.c b/target/i386/cpu.c index
>>>>>>> 24db7ed892..f721d0db78 100644
>>>>>>> --- a/target/i386/cpu.c
>>>>>>> +++ b/target/i386/cpu.c
>>>>>>> @@ -4179,6 +4179,20 @@ static X86CPUDefinition builtin_x86_defs[] =
>>> {
>>>>>>>          .xlevel = 0x8000001E,
>>>>>>>          .model_id = "AMD EPYC-Rome Processor",
>>>>>>>          .cache_info = &epyc_rome_cache_info,
>>>>>>> +        .versions = (X86CPUVersionDefinition[]) {
>>>>>>> +            { .version = 1 },
>>>>>>> +            {
>>>>>>> +                .version = 2,
>>>>>>> +                .props = (PropValue[]) {
>>>>>>> +                    { "ibrs", "on" },
>>>>>>> +                    { "amd-ssbd", "on" },
>>>>>>> +                    { "model-id",
>>>>>>> +                      "AMD EPYC-Rome Processor" },
>>>>>>> +                    { /* end of list */ }
>>>>>>> +                }
>>>>>>> +            },
>>>>>>> +            { /* end of list */ }
>>>>>>> +        }
>>>>>>>      },
>>>>>>>      {
>>>>>>>          .name = "EPYC-Milan",