linux-kernel - RE: [PATCH v3] xen/privcmd: add IOCTL_PRIVCMD_MMAP

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Date:   Tue, 10 Apr 2018 07:53:43 +0000
From:   Paul Durrant <Paul.Durrant@...rix.com>
To:     'Boris Ostrovsky' <boris.ostrovsky@...cle.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Juergen Gross <jgross@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Stefano Stabellini <sstabellini@...nel.org>
Subject: RE: [PATCH v3] xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE

> -----Original Message-----
> From: Boris Ostrovsky [mailto:boris.ostrovsky@...cle.com]
> Sent: 09 April 2018 20:19
> To: Paul Durrant <Paul.Durrant@...rix.com>; xen-devel@...ts.xenproject.org;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Cc: Juergen Gross <jgross@...e.com>; Thomas Gleixner
> <tglx@...utronix.de>; Ingo Molnar <mingo@...hat.com>; Stefano Stabellini
> <sstabellini@...nel.org>
> Subject: Re: [PATCH v3] xen/privcmd: add
> IOCTL_PRIVCMD_MMAP_RESOURCE
> 
> On 04/09/2018 12:36 PM, Boris Ostrovsky wrote:
> > On 04/09/2018 05:36 AM, Paul Durrant wrote:
> >> My recent Xen patch series introduces a new HYPERVISOR_memory_op
> to
> >> support direct priv-mapping of certain guest resources (such as ioreq
> >> pages, used by emulators) by a tools domain, rather than having to access
> >> such resources via the guest P2M.
> >>
> >> This patch adds the necessary infrastructure to the privcmd driver and
> >> Xen MMU code to support direct resource mapping.
> >>
> >> NOTE: The adjustment in the MMU code is partially cosmetic. Xen will
> now
> >>       allow a PV tools domain to map guest pages either by GFN or MFN,
> thus
> >>       the term 'mfn' has been swapped for 'pfn' in the lower layers of the
> >>       remap code.
> >>
> >> Signed-off-by: Paul Durrant <paul.durrant@...rix.com>
> > Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> >
> > I think this will have to wait until 4.18 though, it's somewhat late for
> > current merge window right now.
> 
> 
> Warns on 32-bit ARM build:
> 
>   CC      drivers/xen/privcmd.o
> In file included from /data/upstream/linux-xen/include/linux/kernel.h:14:0,
>                  from /data/upstream/linux-xen/drivers/xen/privcmd.c:11:
> /data/upstream/linux-xen/drivers/xen/privcmd.c: In function
> ‘privcmd_ioctl_mmap_resource’:
> /data/upstream/linux-xen/drivers/xen/privcmd.c:788:33: warning: cast to
> pointer from integer of different size [-Wint-to-pointer-cast]
>     pr_info("pfn[%u] = %p\n", i, (void *)pfns[i]);

I'm glad that was caught. It was a line of debug that was supposed to have been removed.

  Paul

>                                  ^
> /data/upstream/linux-xen/include/linux/printk.h:308:34: note: in
> definition of macro ‘pr_info’
>   printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
>                                   ^~~~~~~~~~~
>   AR      drivers/xen/xen-privcmd.o
> 
> 
> -boris