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Re: [PATCH v3 1/5] x86/microcode: Allow reading microcode revision even if it can't be updated
- To: Jan Beulich <jbeulich@xxxxxxxx>, Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Mon, 19 Jun 2023 17:06:57 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Mon, 19 Jun 2023 16:07:20 +0000
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On 19/06/2023 4:58 pm, Jan Beulich wrote:
> On 19.06.2023 17:49, Andrew Cooper wrote:
>> On 15/06/2023 4:48 pm, Alejandro Vallejo wrote:
>>> diff --git a/xen/arch/x86/cpu/microcode/core.c
>>> b/xen/arch/x86/cpu/microcode/core.c
>>> index e65af4b82e..df7e1df870 100644
>>> --- a/xen/arch/x86/cpu/microcode/core.c
>>> +++ b/xen/arch/x86/cpu/microcode/core.c
>>> @@ -750,11 +750,12 @@ __initcall(microcode_init);
>>> @@ -860,6 +861,9 @@ int __init early_microcode_init(unsigned long
>>> *module_map,
>>> break;
>>> }
>>>
>>> + if ( ucode_ops.collect_cpu_info )
>>> + ucode_ops.collect_cpu_info();
>>> +
>> I still think this wants to be the other side of "ucode loading fully
>> unavailable", just below.
>>
>> I'm confident it will result in easier-to-follow logic.
> Yet wouldn't that be against the purpose of obtaining the ucode
> revision even if loading isn't possible?
No. The logical order of checks is:
if ( !ops.apply )
return; // Fully unavailable
collect_cpu_info();
if ( rev == ~0 || !can_load )
return; // Loading unavailable
// search for blob to load
This form has fewer misleading NULL checks, and doesn't get
printk(XENLOG_WARNING "Microcode loading not available\n"); after
successful microcode actions.
~Andrew
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