linux-kernel - Re: [PATCH] vfio/pci: zap_vma

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Date:   Mon, 24 May 2021 13:46:50 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Cornelia Huck <cohuck@...hat.com>, kvm@...r.kernel.org,
        Jason Gunthorpe <jgg@...dia.com>,
        Eric Auger <eric.auger@...hat.com>
Subject: Re: [PATCH] vfio/pci: zap_vma_ptes() needs MMU

On Sat, 15 May 2021 12:08:56 -0700
Randy Dunlap <rdunlap@...radead.org> wrote:

> zap_vma_ptes() is only available when CONFIG_MMU is set/enabled.
> Without CONFIG_MMU, vfio_pci.o has build errors, so make
> VFIO_PCI depend on MMU.
> 
> riscv64-linux-ld: drivers/vfio/pci/vfio_pci.o: in function `vfio_pci_mmap_open':
> vfio_pci.c:(.text+0x1ec): undefined reference to `zap_vma_ptes'
> riscv64-linux-ld: drivers/vfio/pci/vfio_pci.o: in function `.L0 ':
> vfio_pci.c:(.text+0x165c): undefined reference to `zap_vma_ptes'
> 
> Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver")
> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> Reported-by: kernel test robot <lkp@...el.com>
> Cc: Alex Williamson <alex.williamson@...hat.com>
> Cc: Cornelia Huck <cohuck@...hat.com>
> Cc: kvm@...r.kernel.org
> Cc: Jason Gunthorpe <jgg@...dia.com>
> Cc: Eric Auger <eric.auger@...hat.com>
> ---
>  drivers/vfio/pci/Kconfig |    1 +
>  1 file changed, 1 insertion(+)
> 
> --- linux-next-20210514.orig/drivers/vfio/pci/Kconfig
> +++ linux-next-20210514/drivers/vfio/pci/Kconfig
> @@ -2,6 +2,7 @@
>  config VFIO_PCI
>  	tristate "VFIO support for PCI devices"
>  	depends on VFIO && PCI && EVENTFD
> +	depends on MMU
>  	select VFIO_VIRQFD
>  	select IRQ_BYPASS_MANAGER
>  	help


Yes, these !MMU configs are getting annoying and I don't know of any
demand for vfio in them.  I suspect we were ok with !MMU until
11c4cd07ba11 though, that's where we added zap_vma_ptes usage.  I
updated the Fixes: tag but I suspect either case would reach the same
set of stable trees.  Applied to vfio for-linus branch for v5.13.
Thanks!

Alex