From: Jan Beulich <jbeulich@suse.com>
To: Fouad Hilly <fouad.hilly@cloud.com>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
"Roger Pau Monné" <roger.pau@citrix.com>,
Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v3 1/5] x86: Update x86 low level version check of microcode
Date: Mon, 6 May 2024 10:45:42 +0200 [thread overview]
Message-ID: <1f16e73f-a5a9-4816-8054-81ad0c186030@suse.com> (raw)
In-Reply-To: <20240430124709.865183-2-fouad.hilly@cloud.com>
On 30.04.2024 14:47, Fouad Hilly wrote:
> Update microcode version check at Intel and AMD Level by:
> Preventing the low level code from sending errors if the microcode
> version is not a newer version. this is required to allow developers to do
> ucode loading testing, including the introduction of Intel "min rev" field,
> which requires an override mechanism for newer version checks.
Won't "min rev" checking, for being Intel-only, require quite the opposite,
i.e. leaving more of the checking to vendor specific code?
> Even though
> the check for newer is removed at this level, it still exists at higher
> common level, where by default only newer version will be processed.
> The option to override version check, will be added as part of this patch
> series.
Please avoid wording like "this patch", "this commit", and all the more
"this patch series". Especially this last one will become completely
meaningless once part of a commit message in the tree.
> --- a/xen/arch/x86/cpu/microcode/amd.c
> +++ b/xen/arch/x86/cpu/microcode/amd.c
> @@ -384,11 +384,10 @@ static struct microcode_patch *cf_check cpu_request_microcode(
> }
>
> /*
> - * If the new ucode covers current CPU, compare ucodes and store the
> - * one with higher revision.
> + * If the microcode covers current CPU, then store its
> + * revision.
> */
Nit: This can become a single line comment now, can't it? (Again then in Intel
code.)
> --- a/xen/arch/x86/cpu/microcode/intel.c
> +++ b/xen/arch/x86/cpu/microcode/intel.c
> @@ -294,8 +294,7 @@ static int cf_check apply_microcode(const struct microcode_patch *patch)
>
> result = microcode_update_match(patch);
>
> - if ( result != NEW_UCODE &&
> - !(opt_ucode_allow_same && result == SAME_UCODE) )
> + if ( result == MIS_UCODE )
> return -EINVAL;
I continue to be in trouble with this change, despite the v3 adjustment
you make: If this is needed here, why would a similar change not be needed
for AMD?
Plus the original question remains: Is this actually valid to be changed
right here? IOW despite the somewhat improved patch description I'm still
having difficulty identifying which vendor-independent check this is
redundant with. As opposed to the AMD change further up and ...
> @@ -355,11 +354,10 @@ static struct microcode_patch *cf_check cpu_request_microcode(
> break;
>
> /*
> - * If the new update covers current CPU, compare updates and store the
> - * one with higher revision.
> + * If the microcode covers current CPU, then store its
> + * revision.
> */
> - if ( (microcode_update_match(mc) != MIS_UCODE) &&
> - (!saved || compare_revisions(saved->rev, mc->rev) == NEW_UCODE) )
> + if ( (microcode_update_match(mc) != MIS_UCODE) && !saved )
> saved = mc;
... this one, where I can see that they are about caching of ucode blobs,
which looks to be dealt with by cache maintenance logic in
microcode_update_helper() and microcode_update_cache().
Jan
next prev parent reply other threads:[~2024-05-06 8:46 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-30 12:47 [PATCH v3 0/5] x86/xen-ucode: Introduce --force option Fouad Hilly
2024-04-30 12:47 ` [PATCH v3 1/5] x86: Update x86 low level version check of microcode Fouad Hilly
2024-05-06 8:45 ` Jan Beulich [this message]
2024-05-09 14:33 ` Fouad Hilly
2024-04-30 12:47 ` [PATCH v3 2/5] x86: Refactor microcode_update() hypercall with flags Fouad Hilly
2024-05-06 9:14 ` Jan Beulich
2024-05-09 14:15 ` Fouad Hilly
2024-04-30 12:47 ` [PATCH v3 3/5] x86: Add usage() to print out usage message Fouad Hilly
2024-05-06 8:20 ` Jan Beulich
2024-05-09 13:59 ` Fouad Hilly
2024-04-30 12:47 ` [PATCH v3 4/5] x86: Use getopt to handle command line args Fouad Hilly
2024-05-06 8:21 ` Jan Beulich
2024-05-09 13:59 ` Fouad Hilly
2024-04-30 12:47 ` [PATCH v3 5/5] Add --force option to xen-ucode to override microcode version check Fouad Hilly
2024-05-06 9:39 ` Jan Beulich
2024-05-09 14:31 ` Fouad Hilly
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