From: David Woodhouse <dwmw2@infradead.org> To: Will Deacon <will.deacon@arm.com> Cc: Jerin Jacob <jerin.jacob@caviumnetworks.com>, lorenzo.pieralisi@arm.com, Arnd Bergmann <arnd@arndb.de>, david.daney@cavium.com, catalin.marinas@arm.com, Liviu.Dudau@arm.com, rrichter@cavium.com, hanjun.guo@linaro.org, linux-pci <linux-pci@vger.kernel.org>, bhelgaas@google.com, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2] arm64: pci: add support for pci_mmap_page_range Date: Mon, 20 Mar 2017 14:07:38 +0000 [thread overview] Message-ID: <1490018858.5036.19.camel@infradead.org> (raw) In-Reply-To: <20170320131836.GM17263@arm.com> [-- Attachment #1.1: Type: text/plain, Size: 1703 bytes --] On Mon, 2017-03-20 at 13:18 +0000, Will Deacon wrote: > > The thing is, this *isn't* an architecture-specific interface where you > > get a clean slate. It's a cross-platform interface. Legacy and horrid, > > sure. But it does you no harm. > I don't agree with that: it provides (privileged) userspace with a way to > map non-prefetchable BARs using write-combining memory attributes, which > could lead to mismatched memory attributes against a kernel mapping of the > same BAR and is something that you can't achieve using the sysfs API. I think that's just a bug. I'll add it to my list. We shouldn't be allowing a WC mapping on a non-prefetchable resource, should we? For that matter, I think it allows you mmap a range of MMIO addresses that correspond to an I/O BAR, and on platforms which allow pci_mmap_io, the converse. That seems... suboptimal. > > What *else* don't you like having in /proc? Shall we have a clean slate > > and eliminate *everything* other than actual processes from /proc for > > the next architecture we add to the tree? If not, why not? > It's not about what we like and don't like in /proc, it's about not > promoting legacy that we don't need. If somebody actually needs the /proc > interface, fine, we can support it. But all the people asking for this have > been concerned solely about the sysfs interface, so I'd just like the two > divorced from each other so that we can provide what people are asking for > without pulling in a deprecated interface at the same time. > > This should be straightforward. Sure, but fairly much orthogonal. I'll roll it in. It's fairly much in the noise now I'm this far down the rabbithole... [-- Attachment #1.2: smime.p7s --] [-- Type: application/x-pkcs7-signature, Size: 4938 bytes --] [-- Attachment #2: Type: text/plain, Size: 176 bytes --] _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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From: dwmw2@infradead.org (David Woodhouse) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v2] arm64: pci: add support for pci_mmap_page_range Date: Mon, 20 Mar 2017 14:07:38 +0000 [thread overview] Message-ID: <1490018858.5036.19.camel@infradead.org> (raw) In-Reply-To: <20170320131836.GM17263@arm.com> On Mon, 2017-03-20 at 13:18 +0000, Will Deacon wrote: > > The thing is, this *isn't* an architecture-specific interface where you > > get a clean slate. It's a cross-platform interface. Legacy and horrid, > > sure. But it does you no harm. > I don't agree with that: it provides (privileged) userspace with a way to > map non-prefetchable BARs using write-combining memory attributes, which > could lead to mismatched memory attributes against a kernel mapping of the > same BAR and is something that you can't achieve using the sysfs API. I think that's just a bug. I'll add it to my list. We shouldn't be allowing a WC mapping on a non-prefetchable resource, should we? For that matter, I think it allows you mmap a range of MMIO addresses that correspond to an I/O BAR, and on platforms which allow pci_mmap_io, the converse. That seems... suboptimal. ? > > What *else* don't you like having in /proc? Shall we have a clean slate > > and eliminate *everything* other than actual processes from /proc for > > the next architecture we add to the tree? If not, why not? > It's not about what we like and don't like in /proc, it's about not > promoting legacy that we don't need. If somebody actually needs the /proc > interface, fine, we can support it. But all the people asking for this have > been concerned solely about the sysfs interface, so I'd just like the two > divorced from each other so that we can provide what people are asking for > without pulling in a deprecated interface at the same time. > > This should be straightforward. Sure, but fairly much orthogonal. I'll roll it in. It's fairly much in the noise now I'm this far down the rabbithole... -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/x-pkcs7-signature Size: 4938 bytes Desc: not available URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20170320/fb220219/attachment.bin>
next prev parent reply other threads:[~2017-03-20 14:07 UTC|newest] Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-04-13 21:10 [PATCH v2] arm64: pci: add support for pci_mmap_page_range Jerin Jacob 2016-04-15 13:09 ` Will Deacon 2016-04-15 18:45 ` Arnd Bergmann 2016-04-18 14:01 ` Jerin Jacob 2016-04-18 14:15 ` Arnd Bergmann 2016-04-18 14:53 ` Jerin Jacob 2016-04-18 15:00 ` Arnd Bergmann 2016-04-18 15:21 ` Jerin Jacob 2016-04-18 15:31 ` Arnd Bergmann 2016-04-18 15:40 ` Will Deacon 2016-04-18 17:45 ` Jerin Jacob 2016-04-18 17:46 ` Arnd Bergmann 2017-03-15 21:01 ` David Woodhouse 2017-03-20 13:18 ` Will Deacon 2017-03-20 14:07 ` David Woodhouse [this message] 2017-03-20 14:07 ` David Woodhouse 2016-04-18 13:43 ` Jerin Jacob 2017-03-16 12:17 ` David Woodhouse 2017-03-16 12:17 ` David Woodhouse 2017-03-20 13:21 ` Will Deacon 2017-03-20 13:21 ` Will Deacon
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