From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>, jgg@nvidia.com
Cc: Clint Sbisa <csbisa@amazon.com>,
linux-pci@vger.kernel.org, Bjorn Helgaas <helgaas@kernel.org>,
linux-arm-kernel@lists.infradead.org, will@kernel.org,
catalin.marinas@arm.com, Leon Romanovsky <leon@kernel.org>
Subject: Re: [PATCH] arm64: Enable PCI write-combine resources under sysfs
Date: Thu, 10 Sep 2020 10:46:00 +0100 [thread overview]
Message-ID: <20200910094600.GA22840@e121166-lin.cambridge.arm.com> (raw)
In-Reply-To: <28d333afc73bd854390f8c39691a735040ba5b39.camel@kernel.crashing.org>
[+Jason]
On Tue, Sep 08, 2020 at 09:33:42AM +1000, Benjamin Herrenschmidt wrote:
> On Thu, 2020-09-03 at 12:08 +0100, Lorenzo Pieralisi wrote:
> > > It's been what other architectures have been doing for mroe than a
> > > decade without significant issues... I don't think you should worry
> > > too
> > > much about this.
> >
> > Minus what I wrote above, I agree with you. I'd still be able to
> > understand what this patch changes in the mellanox driver HW
> > handling though - not sure what they expect from
> > arch_can_pci_mmap_wc()
> > returning 1.
>
> I don't know enough to get into the finer details but looking a bit it
> seems when this is set, they allow extra ioctls to create buffers
> mapped with pgprot_writecombine().
>
> I suppose this means faster MMIO backet buffers for small packets (ie,
> non-DMA use case).
>
> Also note that mlx5_ib_test_wc() only uses arch_can_pci_mmap_wc() for a
> non-ROCE ethernet port on a PF... For anyting else, it just seems to
> actually try to do it and see what happens :-)
>
> Leon: Can you clarify the use of arch_can_pci_mmap_wc() in mlx5 and
> whether you see an issue with enabling this on arm64 ?
Hi Jason,
I was wondering if you could help us with this question, we are trying
to understand what enabling arch_can_pci_mmap_wc() on arm64 would cause
in mellanox drivers wrt mappings and whether there is an expected
behaviour behind them, in particular whether there is an implicit
reliance on x86 write-combine arch/interconnect details.
Thanks,
Lorenzo
next prev parent reply other threads:[~2020-09-10 9:46 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-31 15:18 [PATCH] arm64: Enable PCI write-combine resources under sysfs Clint Sbisa
2020-08-31 23:24 ` Benjamin Herrenschmidt
2020-09-01 18:37 ` Bjorn Helgaas
2020-09-01 23:22 ` Benjamin Herrenschmidt
2020-09-02 8:57 ` Will Deacon
2020-09-02 11:32 ` Lorenzo Pieralisi
2020-09-02 14:29 ` Clint Sbisa
2020-09-02 16:47 ` Lorenzo Pieralisi
2020-09-02 17:21 ` Catalin Marinas
2020-09-02 17:54 ` Lorenzo Pieralisi
2020-09-02 23:03 ` Benjamin Herrenschmidt
2020-09-02 23:08 ` Benjamin Herrenschmidt
2020-09-02 23:08 ` Benjamin Herrenschmidt
2020-09-02 23:07 ` Benjamin Herrenschmidt
2020-09-03 11:08 ` Lorenzo Pieralisi
2020-09-03 14:36 ` Clint Sbisa
2020-09-03 22:26 ` Benjamin Herrenschmidt
2020-09-07 23:33 ` Benjamin Herrenschmidt
2020-09-10 9:46 ` Lorenzo Pieralisi [this message]
2020-09-10 10:54 ` Leon Romanovsky
2020-09-10 12:37 ` Jason Gunthorpe
2020-09-10 15:17 ` Lorenzo Pieralisi
2020-09-10 17:10 ` Jason Gunthorpe
2020-09-10 21:46 ` Benjamin Herrenschmidt
2020-09-10 23:29 ` Jason Gunthorpe
2020-09-11 0:39 ` Benjamin Herrenschmidt
2020-09-11 14:21 ` Jason Gunthorpe
2020-09-11 21:42 ` Clint Sbisa
2020-09-14 14:17 ` Jason Gunthorpe
2020-09-14 14:24 ` Clint Sbisa
2020-09-14 14:38 ` Jason Gunthorpe
2020-09-14 21:42 ` Benjamin Herrenschmidt
2020-09-14 22:00 ` Benjamin Herrenschmidt
2020-09-14 22:32 ` Clint Sbisa
2020-09-14 22:57 ` Jason Gunthorpe
2020-09-14 23:25 ` Benjamin Herrenschmidt
2020-09-15 10:18 ` Lorenzo Pieralisi
2020-09-15 11:05 ` Jason Gunthorpe
2020-09-15 23:17 ` Benjamin Herrenschmidt
2020-09-15 23:40 ` Jason Gunthorpe
2020-09-16 7:59 ` Benjamin Herrenschmidt
2020-09-16 12:12 ` Jason Gunthorpe
2020-09-16 14:09 ` Lorenzo Pieralisi
2020-09-16 14:14 ` Jason Gunthorpe
2020-09-16 23:59 ` Benjamin Herrenschmidt
2020-09-17 10:28 ` Lorenzo Pieralisi
2020-09-17 11:32 ` Jason Gunthorpe
2020-09-17 14:01 ` Lorenzo Pieralisi
2020-09-17 16:08 ` Will Deacon
2020-09-16 12:48 ` Leon Romanovsky
2020-09-16 8:33 ` Will Deacon
2020-09-16 8:48 ` Catalin Marinas
2020-09-16 14:15 ` Lorenzo Pieralisi
2020-09-16 17:00 ` Catalin Marinas
2020-09-16 21:29 ` Benjamin Herrenschmidt
2020-09-16 12:08 ` Jason Gunthorpe
2020-09-15 23:00 ` Benjamin Herrenschmidt
2020-09-15 23:12 ` Clint Sbisa
2020-09-14 21:41 ` Benjamin Herrenschmidt
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