linux-kernel - RE: [PATCH 4/7] remoteproc: add warning on resource table cast

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Message-ID: <cdcc435066ff48aebc9b02e7e0b13c8f@SFHDAG7NODE2.st.com>
Date:   Fri, 30 Nov 2018 20:48:16 +0000
From:   Loic PALLARDY <loic.pallardy@...com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnaud POULIQUEN <arnaud.pouliquen@...com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Suman Anna <s-anna@...com>
Subject: RE: [PATCH 4/7] remoteproc: add warning on resource table cast



> -----Original Message-----
> From: Arnd Bergmann <arnd@...db.de>
> Sent: vendredi 30 novembre 2018 15:33
> To: Loic PALLARDY <loic.pallardy@...com>
> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>; Ohad Ben-Cohen
> <ohad@...ery.com>; linux-remoteproc@...r.kernel.org; Linux Kernel
> Mailing List <linux-kernel@...r.kernel.org>; Arnaud POULIQUEN
> <arnaud.pouliquen@...com>; Benjamin Gaignard
> <benjamin.gaignard@...aro.org>; Suman Anna <s-anna@...com>
> Subject: Re: [PATCH 4/7] remoteproc: add warning on resource table cast
> 
> On Thu, Nov 29, 2018 at 10:31 PM Loic Pallardy <loic.pallardy@...com> wrote:
> >
> > Today resource table supports only 32bit address fields.
> > This is not compliant with 64bit platform for which addresses
> > are cast in 32bit.
> > This patch adds warn messages when address cast is done.
> >
> > Signed-off-by: Loic Pallardy <loic.pallardy@...com>
> > ---
> >  drivers/remoteproc/remoteproc_core.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/remoteproc/remoteproc_core.c
> b/drivers/remoteproc/remoteproc_core.c
> > index 18a1bbf820c9..61c954bd695e 100644
> > --- a/drivers/remoteproc/remoteproc_core.c
> > +++ b/drivers/remoteproc/remoteproc_core.c
> > @@ -772,6 +772,10 @@ static int rproc_alloc_carveout(struct rproc *rproc,
> >                 dev_dbg(dev, "carveout mapped 0x%x to %pad\n",
> >                         mem->da, &dma);
> >         } else {
> > +               /* Update device address as undefined by requester */
> > +               if (sizeof(dma_addr_t) > sizeof(u32))
> > +                       dev_warn(dev, "DMA address cast in 32bit to fit resource table
> format\n");
> > +
> >                 mem->da = (u32)dma;
> >         }
> 
> I think this patch is wrong: sizeof(dma_addr_t) is defined to be large enough
> to support any machine that the kernel can run on. If you build a kernel that
> happens to work on an ARM32 platform with LPAE enabled, then this will
> warn every time, even if you are running on a machine that only has a 32-bit
> address space.

I suppose if LPAE is enabled, address space is larger than 32bit.
But I agree it is possible to display a warn only when some information will be lost
due to cast.
I'll propose a new version testing dma address itself and displaying warn only if above 4GB.

Regards,
Loic
> 
>      Arnd