Subject: Re: [PATCH v6 1/4] uio: introduce UIO_MEM_DMA_COHERENT type

From: Greg Kroah-Hartman <[email-masked]>
Date: Fri, 22 Mar 2024 15:30:37 +0100

On Fri, Mar 22, 2024 at 07:16:19AM -0700, Guenter Roeck wrote:
> On Mon, Feb 05, 2024 at 12:01:37PM -0800, Chris Leech wrote:
> > Add a UIO memtype specifically for sharing dma_alloc_coherent
> > memory with userspace, backed by dma_mmap_coherent.
> > 
> > This is mainly for the bnx2/bnx2x/bnx2i "cnic" interface, although there
> > are a few other uio drivers which map dma_alloc_coherent memory and will
> > be converted to use dma_mmap_coherent as well.
> > 
> > Signed-off-by: Nilesh Javali <[email-masked]>
> > Signed-off-by: Chris Leech <[email-masked]>
> > ---
> 
> Building i386:allyesconfig ... failed
> --------------
> Error log:
> drivers/uio/uio.c: In function 'uio_mmap_dma_coherent':
> drivers/uio/uio.c:795:16: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>   795 |         addr = (void *)mem->addr;
>       |                ^

So on 32bit systems phys_addr_t != the same size as (void *)?  How is
that possible?  We also are doing an explicit cast here, how does this
not work?

Ah, do you have CONFIG_X86_PAE enabled?  That would cause that mess,
ick.

> cc1: all warnings being treated as errors
> make[5]: [scripts/Makefile.build:244: drivers/uio/uio.o] Error 1 (ignored)
> drivers/uio/uio_dmem_genirq.c: In function 'uio_dmem_genirq_open':
> drivers/uio/uio_dmem_genirq.c:63:39: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>    63 |                 uiomem->addr = addr ? (phys_addr_t) addr : DMEM_MAP_ERROR;
>       |                                       ^
> drivers/uio/uio_dmem_genirq.c: In function 'uio_dmem_genirq_release':
> drivers/uio/uio_dmem_genirq.c:92:43: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>    92 |                                           (void *) uiomem->addr,
>       |                                           ^
> cc1: all warnings being treated as errors
> make[5]: [scripts/Makefile.build:244: drivers/uio/uio_dmem_genirq.o] Error 1 (ignored)
> drivers/uio/uio_pruss.c: In function 'pruss_probe':
> drivers/uio/uio_pruss.c:194:34: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>   194 |                 p->mem[2].addr = (phys_addr_t) gdev->ddr_vaddr;
>       |                                  ^
> cc1: all warnings being treated as errors
> 
> Caused by this patch and "uio_dmem_genirq: UIO_MEM_DMA_COHERENT conversion" as well
> as "uio_pruss: UIO_MEM_DMA_COHERENT conversion".
> 
> I'd suggest to make uio dependent on 64 bit if 32 bit is no longer supported
> to prevent waste of test builds resources.

Perhaps disable it if PHYS_ADDR_T_64BIT is not enabled?

Chris, can you make up a patch?  Odd that this didn't show up in 0-day
before this, does it not test 32bit builds anymore?

thanks,

greg k-h