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

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Message-ID: <162033393037.4094195.18215062546427210332.stgit@omen>
Date:   Thu, 06 May 2021 14:47:51 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     gregkh@...uxfoundation.org, stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, jgg@...dia.com
Subject: [PATCH 5.11.y, 5.10.y, 5.4.y] vfio: Depend on MMU

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!

 drivers/vfio/Kconfig |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
index 90c0525b1e0c..67d0bf4efa16 100644
--- a/drivers/vfio/Kconfig
+++ b/drivers/vfio/Kconfig
@@ -22,7 +22,7 @@ config VFIO_VIRQFD
 menuconfig VFIO
 	tristate "VFIO Non-Privileged userspace driver framework"
 	select IOMMU_API
-	select VFIO_IOMMU_TYPE1 if (X86 || S390 || ARM || ARM64)
+	select VFIO_IOMMU_TYPE1 if MMU && (X86 || S390 || ARM || ARM64)
 	help
 	  VFIO provides a framework for secure userspace device drivers.
 	  See Documentation/driver-api/vfio.rst for more details.