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Re: [PATCH v3] x86/amd: Address AMD erratum #1485


  • To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 17 Oct 2023 11:21:47 +0200
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  • Cc: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Henry Wang <Henry.Wang@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Delivery-date: Tue, 17 Oct 2023 09:21:57 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 17.10.2023 11:13, Roger Pau Monné wrote:
> On Tue, Oct 17, 2023 at 08:50:45AM +0100, Andrew Cooper wrote:
>> On 17/10/2023 8:44 am, Jan Beulich wrote:
>>> On 13.10.2023 17:38, Alejandro Vallejo wrote:
>>>> Fix adapted off Linux's mailing list:
>>>>   
>>>> https://lore.kernel.org/lkml/D99589F4-BC5D-430B-87B2-72C20370CF57@xxxxxxxxxxxxx/T/#u
>>> Why reference the bug report when there's a proper commit (f454b18e07f5) 
>>> now?
>>> Plus in any event a short summary of the erratum would help if put right 
>>> here
>>> (without needing to look up any documents or follow any links).
>>
>> That is not public information yet.  The erratum number alone is the
>> best we can do at this juncture.
>>>> --- a/xen/arch/x86/cpu/amd.c
>>>> +++ b/xen/arch/x86/cpu/amd.c
>>>> @@ -1004,6 +1004,28 @@ static void cf_check zen2_disable_c6(void *arg)
>>>>    wrmsrl(MSR_AMD_CSTATE_CFG, val & mask);
>>>>  }
>>>>  
>>>> +static void amd_check_erratum_1485(void)
>>>> +{
>>>> +  uint64_t val, chickenbit = (1 << 5);
>>> Linux gives the bit a name. Any reason you don't?
>>
>> There are multiple different names depending on where you look, and none
>> are particularly relevant here.
> 
> Could we make chickenbit const static?
> 
> I would also use ULL just to be on the safe side, because we then copy
> this for a different bit and it explodes.

I guess the way it is resembles what we already have in amd_check_zenbleed().
Also it's not clear to me why besides "const" you also ask for "static".

Jan



 


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