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Re: [PATCH v4 3/4] x86: Read MSR_ARCH_CAPS immediately after early_microcode_init()
- To: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 23 Jun 2023 09:33:56 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Fri, 23 Jun 2023 07:34:17 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 22.06.2023 19:42, Alejandro Vallejo wrote:
> --- a/xen/arch/x86/cpu/microcode/core.c
> +++ b/xen/arch/x86/cpu/microcode/core.c
> @@ -885,5 +885,18 @@ int __init early_microcode_init(unsigned long
> *module_map,
> if ( ucode_mod.mod_end || ucode_blob.size )
> rc = early_microcode_update_cpu();
>
> + /*
> + * MSR_ARCH_CAPS may have appeared after the microcode update.
> + * Reload relevant fields in boot_cpu_data if so because they are
> + * needed in tsx_init().
> + */
> + if ( boot_cpu_data.cpuid_level >= 7 )
> + boot_cpu_data.x86_capability[FEATURESET_7d0]
> + = cpuid_count_edx(7, 0);
> + if ( cpu_has_arch_caps )
> + rdmsr(MSR_ARCH_CAPABILITIES,
> + boot_cpu_data.x86_capability[FEATURESET_m10Al],
> + boot_cpu_data.x86_capability[FEATURESET_m10Ah]);
> +
> return rc;
> }
Did you consider simply calling early_cpu_init() a 2nd time, and then
perhaps from setup.c and only if ucode load didn't report an error?
There's a printk() in there which will want avoiding on the 2nd pass,
but otherwise this would look more future-proof to me.
Jan
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