linux-kernel - Re: [PATCH 0/6] pmem, dax: I/O path enhancements

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1438974391.2293.3.camel@linux.intel.com>
Date:	Fri, 07 Aug 2015 13:06:31 -0600
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Borislav Petkov <bp@...e.de>, "H. Peter Anvin" <hpa@...or.com>,
	Ingo Molnar <mingo@...hat.com>,
	Juergen Gross <jgross@...e.com>, Len Brown <lenb@...nel.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	"Luis R. Rodriguez" <mcgrof@...e.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Toshi Kani <toshi.kani@...com>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH 0/6] pmem, dax: I/O path enhancements

On Fri, 2015-08-07 at 09:47 -0700, Dan Williams wrote:
> On Thu, Aug 6, 2015 at 10:43 AM, Ross Zwisler
> <ross.zwisler@...ux.intel.com> wrote:
> > Patch 5 adds support for the "read flush" _DSM flag, allowing us to change the
> > ND BLK aperture mapping from write-combining to write-back via memremap_pmem().
> >
> > Patch 6 updates the DAX I/O path so that all operations that store data (I/O
> > writes, zeroing blocks, punching holes, etc.) properly synchronize the stores
> > to media using the PMEM API.  This ensures that the data DAX is writing is
> > durable on media before the operation completes.
> >
> > Patches 1-4 are cleanup patches and additions to the PMEM API that make
> > patches 5 and 6 possible.
> >
> > Regarding the choice to add both flush_cache_pmem() and wb_cache_pmem() to the
> > PMEM API, I had initially implemented flush_cache_pmem() as a generic function
> > flush_io_cache_range() in the spirit of flush_cache_range(), etc., in
> > cacheflush.h.  I eventually moved it into the PMEM API because a) it has a
> > common and consistent use of the __pmem annotation, b) it has a clear fallback
> > method for architectures that don't support it, as opposed to APIs in
> > cacheflush.h which would need to be added individually to all other
> > architectures.  It can be argued that the flush API could apply to other uses
> > beyond PMEM such as flushing cache lines associated with other types of
> > sliding MMIO windows.  At this point I'm inclined to have it as part of the
> > PMEM API, and then take on the effort of making it a general cache flusing API
> > if other users come along.
> 
> I'm not convinced.  There are already existing users for invalidating
> a cpu cache and they currently jump through hoops to have cross-arch
> flushing, see drm_clflush_pages().  What the NFIT-BLK driver brings to
> the table is just one more instance where the cpu cache needs to be
> invalidated, and for something so fundamental it is time we had a
> cross arch generic helper.

Fair enough.  I'll move back to the flush_io_cache_range() solution.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/