From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Luis R. Rodriguez" <mcgrof@suse.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Toshi Kani" <toshi.kani@hp.com>,
"Andy Lutomirski" <luto@amacapital.net>,
"Juergen Gross" <jgross@suse.com>,
"Tomi Valkeinen" <tomi.valkeinen@ti.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
linux-fbdev <linux-fbdev@vger.kernel.org>,
"Suresh Siddha" <sbsiddha@gmail.com>,
"Ingo Molnar" <mingo@elte.hu>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Daniel Vetter" <daniel.vetter@ffwll.ch>,
"Dave Airlie" <airlied@redhat.com>,
"Antonino Daplas" <adaplas@gmail.com>,
"Jean-Christophe Plagniol-Villard" <plagnioj@jcrosoft.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
venkatesh.pallipadi@intel.com,
"Stefan Bader" <stefan.bader@canonical.com>,
"Ville Syrjälä" <syrjala@sci.fi>, "Mel Gorman" <mgorman@suse.de>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Borislav Petkov" <bp@suse.de>,
"Davidlohr Bueso" <dbueso@suse.de>,
"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
"David Vrabel" <david.vrabel@citrix.com>,
"Jan Beulich" <jbeulich@suse.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH v7 5/9] PCI: Add pci_iomap_wc() variants
Date: Thu, 25 Jun 2015 10:52:01 +1000 [thread overview]
Message-ID: <1435193521.3790.26.camel@kernel.crashing.org> (raw)
In-Reply-To: <20150625000803.GH11147@wotan.suse.de>
On Thu, 2015-06-25 at 02:08 +0200, Luis R. Rodriguez wrote:
>
> OK thanks I'll proceed with these patches then.
>
> > As for user mappings,
>
> Which APIs were you considering in this regard BTW?
mmap of the generic /sys/bus/pci/.../resource*
> > maybe the right thing to do is to let us do what we do by
> > default with a quirk that can set a flag in pci_dev to disable that
> > behaviour (maybe on a per BAR basis ?).
>
> That might mean it could restrict userspace WC to require devices
> to have WC parts on a full PCI BAR. Although this is restrictive
> having reviewed most WC uses in the kernel I'd think this would be
> a fair compromise to make, but again, if things are still murky
> perhaps best we kiss this idea good bye for now and hope for it
> to come in on future buses or ammendments (if that's even possible?).
>
> > I think the common case is that WC works.
>
> If WC does not I will note one hack which migh be worth mentioning --
> just for
> the record, this was devised as a shortcoming of a device where they
> failed to
> split things properly and that *without* WC performance suffered quite
> a bit so
> they made one full PCI BAR WC and as a work around this:
>
> http://lkml.kernel.org/r/20150416041837.GA5712@hykim-PC
>
> That is for registers that needed it:
>
> write; wmb;
>
> Then if they wanted to wait till the NIC has seen the write, they did:
>
> write; wmb; read;
>
Right, and as I mentioned, on some archs like powerpc (and possibly
more), writel() and co contains an implicit mb()
> Luis--
next prev parent reply other threads:[~2015-06-25 0:53 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-19 22:08 [PATCH v7 0/9] pci: add pci_iomap_wc() and pci_ioremap_wc_bar() Luis R. Rodriguez
2015-06-19 22:08 ` [PATCH v7 1/9] pci: add pci_ioremap_wc_bar() Luis R. Rodriguez
2015-06-19 22:08 ` [PATCH v7 2/9] video: fbdev: i740fb: use arch_phys_wc_add() and pci_ioremap_wc_bar() Luis R. Rodriguez
2015-06-19 22:08 ` [PATCH v7 3/9] video: fbdev: kyrofb: " Luis R. Rodriguez
2015-06-19 22:08 ` [PATCH v7 4/9] video: fbdev: gxt4500: use pci_ioremap_wc_bar() for framebuffer Luis R. Rodriguez
2015-06-19 22:08 ` [PATCH v7 5/9] PCI: Add pci_iomap_wc() variants Luis R. Rodriguez
2015-06-23 22:42 ` Benjamin Herrenschmidt
2015-06-24 16:38 ` Luis R. Rodriguez
2015-06-24 22:05 ` Benjamin Herrenschmidt
2015-06-24 22:29 ` Luis R. Rodriguez
2015-06-24 23:38 ` Benjamin Herrenschmidt
2015-06-25 0:08 ` Luis R. Rodriguez
2015-06-25 0:52 ` Benjamin Herrenschmidt [this message]
2015-06-25 0:58 ` [Xen-devel] " Luis R. Rodriguez
2015-06-25 1:12 ` Benjamin Herrenschmidt
2015-06-25 15:01 ` Casey Leedom
2015-06-25 20:44 ` Arnd Bergmann
2015-06-25 21:40 ` Casey Leedom
2015-06-25 22:51 ` Benjamin Herrenschmidt
2015-06-26 19:31 ` Luis R. Rodriguez
2015-06-26 22:04 ` Benjamin Herrenschmidt
[not found] ` <CAB=NE6XwczF6FYXV=RHyK=7ikVk_tGp+h9ouWPyORNENq4+=Kw@mail.gmail.com>
2015-06-26 23:54 ` [Xen-devel] " Benjamin Herrenschmidt
2015-06-27 1:16 ` Luis R. Rodriguez
2015-06-26 2:02 ` Benjamin Herrenschmidt
2015-06-26 16:24 ` Casey Leedom
2015-06-26 22:00 ` Benjamin Herrenschmidt
2015-07-02 18:49 ` Luis R. Rodriguez
2015-07-02 22:26 ` Benjamin Herrenschmidt
2015-07-03 0:14 ` Casey Leedom
2015-06-19 22:08 ` [PATCH v7 6/9] lib: devres: add pcim_iomap_wc() variants Luis R. Rodriguez
2015-06-19 22:08 ` [PATCH v7 7/9] video: fbdev: arkfb: use arch_phys_wc_add() and pci_iomap_wc() Luis R. Rodriguez
2015-06-19 22:08 ` [PATCH v7 8/9] video: fbdev: s3fb: " Luis R. Rodriguez
2015-06-19 22:08 ` [PATCH v7 9/9] video: fbdev: vt8623fb: " Luis R. Rodriguez
2015-06-23 10:53 ` [PATCH v7 0/9] pci: add pci_iomap_wc() and pci_ioremap_wc_bar() Arnd Bergmann
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