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Re: [Xen-devel] [PATCH] IB/ipath: use arch_phys_wc_add() and require PAT disabled
- To: Doug Ledford <dledford@xxxxxxxxxx>, Mike Marciniszyn <infinipath@xxxxxxxxx>, roland@xxxxxxxxxx, "Hefty, Sean" <sean.hefty@xxxxxxxxx>, Hal Rosenstock <hal.rosenstock@xxxxxxxxx>, linux-rdma@xxxxxxxxxxxxxxx
- From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx>
- Date: Mon, 27 Apr 2015 09:46:21 -0700
- Cc: linux-fbdev <linux-fbdev@xxxxxxxxxxxxxxx>, "Michael S. Tsirkin" <mst@xxxxxxxxxx>, Daniel Vetter <daniel.vetter@xxxxxxxx>, Ville SyrjÃlà <syrjala@xxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, Rickard Strandqvist <rickard_strandqvist@xxxxxxxxxxxxxxxxxx>, Roland Dreier <roland@xxxxxxxxxxxxxxx>, Tomi Valkeinen <tomi.valkeinen@xxxxxx>, Mel Gorman <mgorman@xxxxxxx>, Suresh Siddha <sbsiddha@xxxxxxxxx>, Dave Airlie <airlied@xxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx>, Borislav Petkov <bp@xxxxxxx>, Jean-Christophe Plagniol-Villard <plagnioj@xxxxxxxxxxxx>, Antonino Daplas <adaplas@xxxxxxxxx>, "Luis R. Rodriguez" <mcgrof@xxxxxxxx>, Stefan Bader <stefan.bader@xxxxxxxxxxxxx>, Bjorn Helgaas <bhelgaas@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Vlastimil Babka <vbabka@xxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Mike Marciniszyn <mike.marciniszyn@xxxxxxxxx>, Toshi Kani <toshi.kani@xxxxxx>, Davidlohr Bueso <dbueso@xxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxxxxxx>, David Vrabel <david.vrabel@xxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monnà <roger.pau@xxxxxxxxxx>
- Delivery-date: Mon, 27 Apr 2015 16:46:47 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On Wed, Apr 22, 2015 at 12:26 PM, Luis R. Rodriguez
<mcgrof@xxxxxxxxxxxxxxxx> wrote:
> From: "Luis R. Rodriguez" <mcgrof@xxxxxxxx>
>
> We are burrying direct access to MTRR code support on
> x86 in order to take advantage of PAT. In the future we
> also want to make the default behaviour of ioremap_nocache()
> to use strong UC, use of mtrr_add() on those systems
> would make write-combining void.
>
> In order to help both enable us to later make strong
> UC default and in order to phase out direct MTRR access
> code port the driver over to arch_phys_wc_add() and
> annotate that the device driver requires systems to
> boot with PAT disabled, with the nopat kernel parameter.
>
> This is a worthy compromise given that the ipath device
> driver powers the old HTX bus cards that only work in
> AMD systems, while the newer IB/qib device driver
> powers all PCI-e cards. The ipath device driver is
> obsolete, hardware hard to find and because of this
> this its a reasonable compromise to make to require
> users of ipath to boot with nopat.
Hey folks, I realize its being discussed whether or not to remove the
driver entirely from the kernel but in the meantime, is this a
reasonable compromise ?
Luis
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