Re: [linux-stable-rc:linux-5.4.y 5600/6105] drivers/vfio/vfio_iommu_type1.c:366:22: error: implicit declaration of function 'pte_write'

[Alex Williamson <alex.williamson@redhat.com>]

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On Thu, 6 May 2021 23:51:51 +0800
kernel test robot <lkp@intel.com> wrote:

> Hi Jason,
> 
> First bad commit (maybe != root cause):
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.4.y
> head:   73e74400c797af9bc645d41cfd350b15e3e52d2c
> commit: 3c57ea09365f4a6b32568b8ba6b98ae7d238cb0d [5600/6105] vfio: IOMMU_API should be selected
> config: arm-randconfig-r014-20210506 (attached as .config)
> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 8f5a2a5836cc8e4c1def2bdeb022e7b496623439)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # install arm cross compiling tool for clang build
>         # apt-get install binutils-arm-linux-gnueabi
>         # https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/commit/?id=3c57ea09365f4a6b32568b8ba6b98ae7d238cb0d
>         git remote add linux-stable-rc https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
>         git fetch --no-tags linux-stable-rc linux-5.4.y
>         git checkout 3c57ea09365f4a6b32568b8ba6b98ae7d238cb0d
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=arm 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All errors (new ones prefixed by >>):
> 
> >> drivers/vfio/vfio_iommu_type1.c:366:22: error: implicit declaration of function 'pte_write' [-Werror,-Wimplicit-function-declaration]  
>            if (write_fault && !pte_write(*ptep))
>                                ^
> >> drivers/vfio/vfio_iommu_type1.c:369:10: error: implicit declaration of function 'pte_pfn' [-Werror,-Wimplicit-function-declaration]  
>                    *pfn = pte_pfn(*ptep);
>                           ^
>    drivers/vfio/vfio_iommu_type1.c:369:10: note: did you mean 'put_pfn'?
>    drivers/vfio/vfio_iommu_type1.c:327:12: note: 'put_pfn' declared here
>    static int put_pfn(unsigned long pfn, int prot)
>               ^
> >> drivers/vfio/vfio_iommu_type1.c:371:2: error: implicit declaration of function 'pte_unmap' [-Werror,-Wimplicit-function-declaration]  
>            pte_unmap_unlock(ptep, ptl);
>            ^
>    include/linux/mm.h:1988:2: note: expanded from macro 'pte_unmap_unlock'
>            pte_unmap(pte);                                 \
>            ^
>    3 errors generated.


We need to fit in an MMU dependency for VFIO_IOMMU_TYPE1.  The IOMMU_API
dependency for vfio itself is real.  We could just turn everything off
for MMU (who really cares?) but theoretically VFIO_NOIOMMU support
could be used in some weird way with !MMU.  If VFIO tries to select
something whose dependency isn't met we get Kconfig errors, so I think
the right answer is:

diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
index 9dc95024afae..2c3baeabf094 100644
--- a/drivers/vfio/Kconfig
+++ b/drivers/vfio/Kconfig
@@ -1,8 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0-only
 config VFIO_IOMMU_TYPE1
 	tristate
-	depends on VFIO
-	default n
+	depends on VFIO && MMU
+	default VFIO if (X86 || S390 || ARM || ARM64)
 
 config VFIO_IOMMU_SPAPR_TCE
 	tristate
@@ -22,7 +22,6 @@ config VFIO_VIRQFD
 menuconfig VFIO
 	tristate "VFIO Non-Privileged userspace driver framework"
 	select IOMMU_API
-	select VFIO_IOMMU_TYPE1 if (X86 || S390 || ARM || ARM64)
 	help
 	  VFIO provides a framework for secure userspace device drivers.
 	  See Documentation/driver-api/vfio.rst for more details.

Better options?  Thanks,

Alex