Add "dis_ucode_ldr" to linux boot options for Recovery Mode

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Add "dis_ucode_ldr" to linux boot options for Recovery Mode

Jeroen Bobbeldijk
Hi,

Due to some recent problems with a microcode update which broke booting of some laptops I suggest adding "dis_ucode_ldr" to recovery mode boot options to allow booting after a bad microcode update.

See the following topics that describe the problems:

When such problems occur it's very hard to see that the microcode loading is the issue, the booting just hangs at the purple screen, even removing "quiet splash" will not show the error.  

Kind regards,

Jeroen

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Re: Add "dis_ucode_ldr" to linux boot options for Recovery Mode

Tyler Hicks-2
On 2019-06-05 10:03:06, Jeroen Bobbeldijk wrote:

> Hi,
>
> Due to some recent problems with a microcode update which broke booting of
> some laptops I suggest adding "dis_ucode_ldr" to recovery mode boot options
> to allow booting after a bad microcode update.
>
> See the following topics that describe the problems:
>  - https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1829620
>  - https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/issues/1
>
> When such problems occur it's very hard to see that the microcode loading
> is the issue, the booting just hangs at the purple screen, even removing
> "quiet splash" will not show the error.

I really like this idea. Thanks for mentioning it.

Please open a bug report here:

 https://bugs.launchpad.net/ubuntu/+source/grub2/+filebug

We'll need to double check that dis_ucode_ldr works as expected across
all architectures. Otherwise, I can't think of any other technical
blockers to doing this.

Tyler

>
> Kind regards,
>
> Jeroen

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Re: Add "dis_ucode_ldr" to linux boot options for Recovery Mode

Jeroen Bobbeldijk
Thanks. I'll open a report for grub2.
According to the docs, dis_ucode_ldr is x86 only (arch/x86/kernel/cpu/microcode/core.c), so my guess is that it will be ignored for other architectures. According to the kernel code, dis_ucode_ldr works for both AMD and Intel.
I have some time tomorrow on test this on a ARM device.

Jeroen

On Wed, Jun 5, 2019 at 7:49 PM Tyler Hicks <[hidden email]> wrote:
On 2019-06-05 10:03:06, Jeroen Bobbeldijk wrote:
> Hi,
>
> Due to some recent problems with a microcode update which broke booting of
> some laptops I suggest adding "dis_ucode_ldr" to recovery mode boot options
> to allow booting after a bad microcode update.
>
> See the following topics that describe the problems:
>  - https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1829620
>  - https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/issues/1
>
> When such problems occur it's very hard to see that the microcode loading
> is the issue, the booting just hangs at the purple screen, even removing
> "quiet splash" will not show the error.

I really like this idea. Thanks for mentioning it.

Please open a bug report here:

 https://bugs.launchpad.net/ubuntu/+source/grub2/+filebug

We'll need to double check that dis_ucode_ldr works as expected across
all architectures. Otherwise, I can't think of any other technical
blockers to doing this.

Tyler

>
> Kind regards,
>
> Jeroen

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> Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel


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Re: Add "dis_ucode_ldr" to linux boot options for Recovery Mode

Tyler Hicks-2
On 2019-06-05 20:00:54, Jeroen Bobbeldijk wrote:
> Thanks. I'll open a report for grub2.
> According to the docs, dis_ucode_ldr is x86 only
> (arch/x86/kernel/cpu/microcode/core.c), so my guess is that it will be
> ignored for other architectures. According to the kernel code,
> dis_ucode_ldr works for both AMD and Intel.

Agreed on all the above.

For anyone else following along, Jeroen opened the following bug report:

 https://launchpad.net/bugs/1831789

> I have some time tomorrow on test this on a ARM device.

After taking a look at the grub2 code, it looks like it'll be easy
enough to only inject the dis_ucode_ldr option on x86. There's no need
to test that option on other architectures at this time. Thanks for the
offer, though.

Tyler

>
> Jeroen
>
> On Wed, Jun 5, 2019 at 7:49 PM Tyler Hicks <[hidden email]> wrote:
>
> > On 2019-06-05 10:03:06, Jeroen Bobbeldijk wrote:
> > > Hi,
> > >
> > > Due to some recent problems with a microcode update which broke booting
> > of
> > > some laptops I suggest adding "dis_ucode_ldr" to recovery mode boot
> > options
> > > to allow booting after a bad microcode update.
> > >
> > > See the following topics that describe the problems:
> > >  - https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1829620
> > >  -
> > https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/issues/1
> > >
> > > When such problems occur it's very hard to see that the microcode loading
> > > is the issue, the booting just hangs at the purple screen, even removing
> > > "quiet splash" will not show the error.
> >
> > I really like this idea. Thanks for mentioning it.
> >
> > Please open a bug report here:
> >
> >  https://bugs.launchpad.net/ubuntu/+source/grub2/+filebug
> >
> > We'll need to double check that dis_ucode_ldr works as expected across
> > all architectures. Otherwise, I can't think of any other technical
> > blockers to doing this.
> >
> > Tyler
> >
> > >
> > > Kind regards,
> > >
> > > Jeroen
> >
> > > --
> > > ubuntu-devel mailing list
> > > [hidden email]
> > > Modify settings or unsubscribe at:
> > https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel
> >
> >

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