linux-kernel - Re: [PATCH 5.11.y, 5.10.y, 5.4.y] vfio: Depend on MMU

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Date:   Thu, 6 May 2021 18:10:53 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     gregkh@...uxfoundation.org, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5.11.y, 5.10.y, 5.4.y] vfio: Depend on MMU

On Thu, May 06, 2021 at 02:47:51PM -0600, Alex Williamson wrote:
> From: Jason Gunthorpe <jgg@...dia.com>
> 
> commit b2b12db53507bc97d96f6b7cb279e831e5eafb00 upstream
> 
> VFIO_IOMMU_TYPE1 does not compile with !MMU:
> 
> ../drivers/vfio/vfio_iommu_type1.c: In function 'follow_fault_pfn':
> ../drivers/vfio/vfio_iommu_type1.c:536:22: error: implicit declaration of function 'pte_write'; did you mean 'vfs_write'? [-Werror=implicit-function-declaration]
> 
> So require it.
> 
> Suggested-by: Cornelia Huck <cohuck@...hat.com>
> Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
> Message-Id: <0-v1-02cb5500df6e+78-vfio_no_mmu_jgg@...dia.com>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> Cc: stable@...r.kernel.org # 5.11.y, 5.10.y, 5.4.y
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> 
> The noted stable branches include upstream commit 179209fa1270
> ("vfio: IOMMU_API should be selected") without the follow-up commit
> b2b12db53507 ("vfio: Depend on MMU"), which should have included a
> Fixes: tag for the prior commit.  Without this latter commit, we're
> susceptible to randconfig failures with !MMU configs.  Thanks!

Right. It would also be a fine solution to not include '1792 in any
stable branches either

Jason