linux-kernel - Re: [PATCH] iommu/amd: Override wrong IVRS IOAPIC on Raven Ridge systems

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Message-ID: <20190814085557.GB24321@8bytes.org>
Date:   Wed, 14 Aug 2019 10:55:57 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/amd: Override wrong IVRS IOAPIC on Raven Ridge
 systems

On Tue, Aug 13, 2019 at 11:58:48AM +0800, Kai-Heng Feng wrote:
> at 23:39, Joerg Roedel <joro@...tes.org> wrote:
> 
> > On Thu, Aug 08, 2019 at 06:17:07PM +0800, Kai-Heng Feng wrote:
> > > Raven Ridge systems may have malfunction touchpad or hang at boot if
> > > incorrect IVRS IOAPIC is provided by BIOS.
> > > 
> > > Users already found correct "ivrs_ioapic=" values, let's put them inside
> > > kernel to workaround buggy BIOS.
> > 
> > Will that still work when a fixed BIOS for these laptops is released?
> 
> Do you mean that we should stop applying these quirks once a BIOS fix is
> confirmed?

My concern is just that these quirks break some systems that don't need
them.

> We can modify the quirk to compare BIOS version, if there’s an unlikely BIOS
> update really fixes the issue.
> Before that happens, I think it’s OK to let the quirks stay this way.

A BIOS version check is not making things better here as it might lock
out systems that need the quirk. I think we can leave it as it for now,
but can you create a new file amd_iommu_quirks.c and move the code
there. And in the struct and function names please make clear that it is
about ivrs-quirks.


Regards,

	Joerg