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[209.85.220.65]) by mx.google.com with SMTPS id v21sor16762854lfi.6.2019.07.30.07.52.16 for (Google Transport Security); Tue, 30 Jul 2019 07:52:16 -0700 (PDT) Received-SPF: pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=iuQpUu6a; spf=pass (google.com: domain of jrdr.linux@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=jrdr.linux@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=vLDKuH+/Y6R1wGAQGSCIi/9agKk/j9gR7pNqj2Ro2Ic=; b=iuQpUu6a8JnbGLjoBITZrEilnUrTWiH26PXOZvr0eJQhTGXYXPQKMEzNw2wB2Zdhwg O1s79fuH/+qKj9qM+F5N7WUORuY3bi2XPxK5gT8Guf2uZd9D6oyAtYDwhskz/FMsfn6o lKk6nD1IBmzrEbMo1z8fbSNSoKGZUfXjLfcnm5mKawQB8u+vap+bsQ1AUfdjGTiXN2ty tL6eFXIjDfZ571OcOPQwvXVAUX+46G+xpgSdufwNKOjBmDF3XP8A7mx0CfXSR6UXqbUn dguHNLtM+ir+qgid1b0WJ9SI3b8hxcX2P6U5NkAvYIDJKRzUwkVnKHJszs5C7d/SjcoV C0AQ== X-Google-Smtp-Source: APXvYqwtNV8PHczquSPB8e+BmF7PEr+3WvMBui8pMbhp0rAOkLkZq6TteMkvwzTbZj0eIDgOEAic/3pWWOYVMC6LbUU= X-Received: by 2002:a19:c1cc:: with SMTP id r195mr53854149lff.95.1564498336043; Tue, 30 Jul 2019 07:52:16 -0700 (PDT) MIME-Version: 1.0 References: <20190215024830.GA26477@jordon-HP-15-Notebook-PC> <20190728180611.GA20589@mail-itl> <20190729133642.GQ1250@mail-itl> <20190730142233.GR1250@mail-itl> In-Reply-To: <20190730142233.GR1250@mail-itl> From: Souptick Joarder Date: Tue, 30 Jul 2019 20:22:02 +0530 Message-ID: Subject: Re: [Xen-devel] [PATCH v4 8/9] xen/gntdev.c: Convert to use vm_map_pages() To: =?UTF-8?Q?Marek_Marczykowski=2DG=C3=B3recki?= Cc: Boris Ostrovsky , Andrew Morton , Matthew Wilcox , Michal Hocko , Juergen Gross , Russell King - ARM Linux , robin.murphy@arm.com, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, Linux-MM , stable@vger.kernel.org, Greg KH Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jul 30, 2019 at 7:52 PM Marek Marczykowski-G=C3=B3recki wrote: > > On Tue, Jul 30, 2019 at 10:05:42AM -0400, Boris Ostrovsky wrote: > > On 7/30/19 2:03 AM, Souptick Joarder wrote: > > > On Mon, Jul 29, 2019 at 7:06 PM Marek Marczykowski-G=C3=B3recki > > > wrote: > > >> On Mon, Jul 29, 2019 at 02:02:54PM +0530, Souptick Joarder wrote: > > >>> On Mon, Jul 29, 2019 at 1:35 PM Souptick Joarder wrote: > > >>>> On Sun, Jul 28, 2019 at 11:36 PM Marek Marczykowski-G=C3=B3recki > > >>>> wrote: > > >>>>> On Fri, Feb 15, 2019 at 08:18:31AM +0530, Souptick Joarder wrote: > > >>>>>> Convert to use vm_map_pages() to map range of kernel > > >>>>>> memory to user vma. > > >>>>>> > > >>>>>> map->count is passed to vm_map_pages() and internal API > > >>>>>> verify map->count against count ( count =3D vma_pages(vma)) > > >>>>>> for page array boundary overrun condition. > > >>>>> This commit breaks gntdev driver. If vma->vm_pgoff > 0, vm_map_pa= ges > > >>>>> will: > > >>>>> - use map->pages starting at vma->vm_pgoff instead of 0 > > >>>> The actual code ignores vma->vm_pgoff > 0 scenario and mapped > > >>>> the entire map->pages[i]. Why the entire map->pages[i] needs to be= mapped > > >>>> if vma->vm_pgoff > 0 (in original code) ? > > >> vma->vm_pgoff is used as index passed to gntdev_find_map_index. It's > > >> basically (ab)using this parameter for "which grant reference to map= ". > > >> > > >>>> are you referring to set vma->vm_pgoff =3D 0 irrespective of value= passed > > >>>> from user space ? If yes, using vm_map_pages_zero() is an alternat= e > > >>>> option. > > >> Yes, that should work. > > > I prefer to use vm_map_pages_zero() to resolve both the issues. Alter= natively > > > the patch can be reverted as you suggested. Let me know you opinion a= nd wait > > > for feedback from others. > > > > > > Boris, would you like to give any feedback ? > > > > vm_map_pages_zero() looks good to me. Marek, does it work for you? > > Yes, replacing vm_map_pages() with vm_map_pages_zero() fixes the > problem for me. Marek, I can send a patch for the same if you are ok. We need to cc stable as this changes are available in 5.2.4. > > -- > Best Regards, > Marek Marczykowski-G=C3=B3recki > Invisible Things Lab > A: Because it messes up the order in which people normally read text. > Q: Why is top-posting such a bad thing?