From: Ashok Raj <ashok.raj@intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ashok Raj <ashok.raj@intel.com>
Subject: Re: [PATCH 2/2] x86/microcode: Add a "microcode=" command line option
Date: Fri, 9 Jun 2023 08:37:21 -0700 [thread overview]
Message-ID: <ZINHMRR28jre+Bw/@a4bf019067fa.jf.intel.com> (raw)
In-Reply-To: <20230609122828.GBZIMa7OtCIpSkYGxV@fat_crate.local>
On Fri, Jun 09, 2023 at 02:28:28PM +0200, Borislav Petkov wrote:
> On Wed, Jun 07, 2023 at 06:55:39PM -0700, Ashok Raj wrote:
> > When end user changes the behavior, isn't it against the design
> > specification? And if so, should that result in kernel being tainted
> > after a reload?
>
> That's a chicken bit and should not be used usually. I'm adding it just
> in case.
How about a debugfs opt-out instead? Say something like
/sys/kernel/debug/microcode/debug_control?
Since the code doesn't use this in the early loading, it appears we can
drop the cmdline entirely?
>
> > Is this reload on all threads required by all models, or only certain
> > models? I was wondering if the forced reload could be limited to only
> > affected CPUs instead of doing it on all unconditionally.
>
> Unconditionally.
Thanks, this simplifies.
Since this is quite different from what the "typical" HT behavior w.r.t ,
microcode, maybe good to document this behavior in microcode.rst.
If the user switches the expected flow, should the code "taint" if its opted out?
>
> > Shouldn't the "control" be under LATE_LOADING? Since this only controls
> > late-loading behavior?
>
> No, that's a bitfield and is going to be used for other flags, if
> needed and which are not necessarily late-loading related.
My .000002c. Maybe add such sysfs control only when we really need one,
but should not include debug use.
next prev parent reply other threads:[~2023-06-09 15:37 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-05 14:13 [PATCH 1/2] x86/microcode/AMD: Load late on both threads too Borislav Petkov
2023-06-05 14:13 ` [PATCH 2/2] x86/microcode: Add a "microcode=" command line option Borislav Petkov
2023-06-08 1:55 ` Ashok Raj
2023-06-09 12:28 ` Borislav Petkov
2023-06-09 15:37 ` Ashok Raj [this message]
2023-06-12 9:06 ` Borislav Petkov
2023-06-12 9:20 ` [tip: x86/microcode] " tip-bot2 for Borislav Petkov (AMD)
2023-06-12 15:26 ` [PATCH 2/2] " Thomas Gleixner
2023-06-12 15:42 ` Borislav Petkov
2023-06-12 16:04 ` Borislav Petkov
2023-06-12 17:23 ` Thomas Gleixner
2023-06-13 8:32 ` Borislav Petkov
2023-06-07 19:36 ` [PATCH 1/2] x86/microcode/AMD: Load late on both threads too Dave Hansen
2023-06-07 20:03 ` Borislav Petkov
2023-06-07 20:15 ` Dave Hansen
2023-08-16 20:17 ` Jim Mattson
2023-08-16 21:18 ` Borislav Petkov
2023-08-16 21:23 ` Jim Mattson
2023-08-16 21:30 ` Borislav Petkov
2023-08-16 21:36 ` Jim Mattson
2023-08-16 21:58 ` Borislav Petkov
2023-08-16 22:37 ` Jim Mattson
2023-08-17 15:40 ` Borislav Petkov
2023-08-17 18:02 ` Peter Shier
2023-08-18 8:43 ` Borislav Petkov
2023-06-12 9:20 ` [tip: x86/microcode] " tip-bot2 for Borislav Petkov (AMD)
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