From: Bharat Kumar Gogada <bharatku@xilinx.com>
To: Matthew Wilcox <willy@infradead.org>,
Dan Williams <dan.j.williams@intel.com>
Cc: "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
"jack@suse.cz" <jack@suse.cz>
Subject: RE: DAX filesystem support on ARMv8
Date: Thu, 14 Nov 2019 06:54:43 +0000 [thread overview]
Message-ID: <MN2PR02MB6336070627E66ED8AE646BACA5710@MN2PR02MB6336.namprd02.prod.outlook.com> (raw)
In-Reply-To: <20191112220212.GC7934@bombadil.infradead.org>
>
> On Tue, Nov 12, 2019 at 09:15:18AM -0800, Dan Williams wrote:
> > On Mon, Nov 11, 2019 at 6:12 PM Bharat Kumar Gogada
> <bharatku@xilinx.com> wrote:
> > >
> > > Hi All,
> > >
> > > As per Documentation/filesystems/dax.txt
> > >
> > > The DAX code does not work correctly on architectures which have
> > > virtually mapped caches such as ARM, MIPS and SPARC.
> > >
> > > Can anyone please shed light on dax filesystem issue w.r.t ARM architecture
> ?
> >
> > The concern is VIVT caches since the kernel will want to flush pmem
> > addresses with different virtual addresses than what userspace is
> > using. As far as I know, ARMv8 has VIPT caches, so should not have an
> > issue. Willy initially wrote those restrictions, but I am assuming
> > that the concern was managing the caches in the presence of virtual
> > aliases.
>
> The kernel will also access data at different virtual addresses from userspace.
> So VIVT CPUs will be mmap/read/write incoherent, as well as being flush
> incoherent.
Thanks a lot Wilcox and Dan for clarification.
So the above restriction only applies to ARM architectures with VIVT caches and not
for VIPT caches.
Regards,
Bharat
next prev parent reply other threads:[~2019-11-14 6:54 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-12 2:12 DAX filesystem support on ARMv8 Bharat Kumar Gogada
2019-11-12 9:49 ` Jan Kara
2019-11-12 17:15 ` Dan Williams
2019-11-12 22:02 ` Matthew Wilcox
2019-11-14 6:54 ` Bharat Kumar Gogada [this message]
2019-12-01 18:54 ` Jon Masters
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