netdev - Re: [PATCH] uio-hv-generic: store physical addresses instead of virtual

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Date:   Fri, 9 Dec 2016 09:28:44 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        netdev@...r.kernel.org, Haiyang Zhang <haiyangz@...rosoft.com>,
        linux-kernel@...r.kernel.org, devel@...uxdriverproject.org
Subject: Re: [PATCH] uio-hv-generic: store physical addresses instead of
 virtual

On Fri,  9 Dec 2016 12:44:40 +0100
Arnd Bergmann <arnd@...db.de> wrote:

> gcc warns about the newly added driver when phys_addr_t is wider than
> a pointer:
> 
> drivers/uio/uio_hv_generic.c: In function 'hv_uio_mmap':
> drivers/uio/uio_hv_generic.c:71:17: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>     virt_to_phys((void *)info->mem[mi].addr) >> PAGE_SHIFT,
> drivers/uio/uio_hv_generic.c: In function 'hv_uio_probe':
> drivers/uio/uio_hv_generic.c:140:5: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>    = (phys_addr_t)dev->channel->ringbuffer_pages;
> drivers/uio/uio_hv_generic.c:147:3: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>    (phys_addr_t)vmbus_connection.int_page;
> drivers/uio/uio_hv_generic.c:153:3: error: cast from pointer to integer of different size [-Werror=pointer-to-int-cast]
>    (phys_addr_t)vmbus_connection.monitor_pages[1];
> 
> I can't see why we store a virtual address in a phys_addr_t here,
> as the only user of that variable converts it into a physical
> address anyway, so this moves the conversion to where it logically
> fits according to the types.
> 
> Fixes: 95096f2fbd10 ("uio-hv-generic: new userspace i/o driver for VMBus")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Thanks, the code was inherited from outside, and only tested on x86_64.
Not sure which platform and GCC version generates the warning, was this just W=1?

Acked-by: Stephen Hemminger <sthemmin@...rosoft.com>