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Re: [PATCH CPU v1] cpuid: initialize cpuinfo with boot_cpu_data
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 11 Feb 2022 11:32:45 +0100
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Norbert Manthey <nmanthey@xxxxxxxxx>
- Delivery-date: Fri, 11 Feb 2022 10:32:58 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 11.02.2022 10:02, Roger Pau Monné wrote:
> On Fri, Feb 11, 2022 at 08:23:27AM +0100, Norbert Manthey wrote:
>> When re-identifying CPU data, we might use uninitialized data when
>> checking for the cache line property to adapt the cache
>> alignment. The data that depends on this uninitialized read is
>> currently not forwarded.
>>
>> To avoid problems in the future, initialize the data cpuinfo
>> structure before re-identifying the CPU again.
>>
>> The trace to hit the uninitialized read reported by Coverity is:
>>
>> bool recheck_cpu_features(unsigned int cpu)
>> ...
>> struct cpuinfo_x86 c;
>> ...
>> identify_cpu(&c);
>>
>> void identify_cpu(struct cpuinfo_x86 *c)
>> ...
>> generic_identify(c)
>>
>> static void generic_identify(struct cpuinfo_x86 *c)
>> ...
>
> Would it be more appropriate for generic_identify to also set
> x86_cache_alignment like it's done in early_cpu_init?
>
> generic_identify already re-fetches a bunch of stuff that's also
> set by early_cpu_init for the BSP.
This would be an option, but how sure are you that there isn't
(going to be) another field with similar properties? We better
wouldn't require _everything_ to be re-filled in generic_identify().
Jan
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