linux-kernel - Re: [Patch V1 2/7] x86/microcode/intel: Remove retries on early microcode load

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Date:   Fri, 2 Dec 2022 17:48:57 -0800
From:   Ashok Raj <ashok.raj@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     Borislav Petkov <bp@...en8.de>, X86-kernel <x86@...nel.org>,
        "LKML Mailing List" <linux-kernel@...r.kernel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>, <alison.schofield@...el.com>,
        <reinette.chatre@...el.com>, Ashok Raj <ashok.raj@...el.com>
Subject: Re: [Patch V1 2/7] x86/microcode/intel: Remove retries on early
 microcode load

On Fri, Dec 02, 2022 at 08:01:54PM +0100, Thomas Gleixner wrote:
> On Tue, Nov 29 2022 at 13:08, Ashok Raj wrote:
> > Microcode loading can fail. This happens today when handling mixed
> > steppings. But it can also happen for other reasons such as corrupted
> > image, Security Version Number (SVN) preventing anti-rollback,
> > dependencies on BIOS loaded microcode image for some capabilities.
> >
> > When the microcode loading fails, the kernel will quietly hang at boot.
> > This has been observed by end users (Links below) who had to revert their
> > microcode packages in order to boot again.
> >
> > The hang is due to an infinite retry loop. The retries were in place to
> > support systems with mixed steppings. Now that mixed steppings are no
> > longer supported, there is only one microcode image at a time. Any retries
> > will simply reattempt to apply the same image over and over without making
> > progress.
> >
> > Some possible past bugs that could be due to this bug are below.
> >
> > There is no direct evidence that these end user issues were caused by this
> > retry loop. However, the early boot hangs along with reverting the
> > microcode update workaround provide strong circumstantial evidence to
> > support the theory that they are linked.
> >
> > Remove the retry loop and only attempt to apply microcode once.
> 
> Very concise and informative changelog. See, you can do it :)
> 
> > Link: https://bugs.launchpad.net/ubuntu/+source/intel-microcode/+bug/1911959
> > Link: https://forums.linuxmint.com/viewtopic.php?p=1827032#1827032
> > Link: https://askubuntu.com/questions/1291486/boot-crash-after-latest-update-of-intel-microcode-nov-11-2020
> > Fixes: 06b8534cb728 ("x86/microcode: Rework microcode loading")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Ashok Raj <ashok.raj@...el.com>
> 
> Nit: Can you order the tags according to the tip documentation next time
>      please?
> 
> Reviewed-by: Thomas Gleixner <tglx@...utronix.de>

Thanks!. Dave Hansen gave me script to order them correctly :-).. I'll fix
when i repost them.