From: Dan Williams <dan.j.williams@intel.com>
To: David Laight <David.Laight@aculab.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
"Luck, Tony" <tony.luck@intel.com>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>, stable <stable@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Paul Mackerras <paulus@samba.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Erwin Tsaur <erwin.tsaur@intel.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
linux-nvdimm <linux-nvdimm@lists.01.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 0/2] Replace and improve "mcsafe" with copy_safe()
Date: Mon, 4 May 2020 11:33:46 -0700 [thread overview]
Message-ID: <CAPcyv4i8V9FCuTHZG2RG9o3vjrMmLkv40-41MwLBO8tZWUsZ5Q@mail.gmail.com> (raw)
In-Reply-To: <a4aabe6f2ca649779a772a5f0365af6f@AcuMS.aculab.com>
On Sun, May 3, 2020 at 5:57 AM David Laight <David.Laight@aculab.com> wrote:
>
> From: Linus Torvalds
> > Sent: 01 May 2020 19:29
> ...
> > And as DavidL pointed out - if you ever have "iomem" as a source or
> > destination, you need yet another case. Not because they can take
> > another kind of fault (although on some platforms you have the machine
> > checks for that too), but because they have *very* different
> > performance profiles (and the ERMS "rep movsb" sucks baby donkeys
> > through a straw).
>
>
> I was actually thinking that the nvdimm accesses need to be treated
> much more like (cached) memory mapped io space than normal system
> memory.
> So treating them the same as "iomem" and then having access functions
> that report access failures (which the current readq() doesn't)
> might make sense.
While I agree that something like copy_mc_iomem_to_{user,kernel} could
have users, nvdimm is not one of them.
> If you are using memory that 'might fail' for kernel code or data
> you really get what you deserve.
nvdimms are no less "might fail" than DRAM, recall that some nvdimms
are just DRAM with a platform promise that their contents are battery
backed.
> OTOH system response to PCIe errors is currently rather problematic.
> Mostly reads time out and return ~0u.
> This can be checked for and, if possibly valid, a second location read.
Yes, the ambiguous ~0u return needs careful handling.
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next prev parent reply other threads:[~2020-05-04 18:34 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-30 8:24 [PATCH v2 0/2] Replace and improve "mcsafe" with copy_safe() Dan Williams
2020-04-30 8:25 ` [PATCH v2 1/2] copy_safe: Rename memcpy_mcsafe() to copy_safe() Dan Williams
2020-04-30 8:25 ` [PATCH v2 2/2] x86/copy_safe: Introduce copy_safe_fast() Dan Williams
2020-04-30 14:02 ` [PATCH v2 0/2] Replace and improve "mcsafe" with copy_safe() Linus Torvalds
2020-04-30 16:51 ` Andy Lutomirski
2020-04-30 17:17 ` Linus Torvalds
2020-04-30 18:42 ` Andy Lutomirski
2020-04-30 19:22 ` Luck, Tony
2020-04-30 19:50 ` Linus Torvalds
2020-04-30 20:25 ` Luck, Tony
2020-04-30 23:52 ` Dan Williams
2020-05-01 0:10 ` Linus Torvalds
2020-05-01 0:23 ` Andy Lutomirski
2020-05-01 0:39 ` Linus Torvalds
2020-05-01 1:10 ` Andy Lutomirski
2020-05-01 14:09 ` Luck, Tony
2020-05-03 0:29 ` Andy Lutomirski
2020-05-04 20:05 ` Luck, Tony
2020-05-04 20:26 ` Andy Lutomirski
2020-05-04 21:30 ` Dan Williams
2020-05-01 0:24 ` Linus Torvalds
2020-05-01 1:20 ` Andy Lutomirski
2020-05-01 1:21 ` Dan Williams
2020-05-01 18:28 ` Linus Torvalds
2020-05-01 20:17 ` Dave Hansen
2020-05-03 12:57 ` David Laight
2020-05-04 18:33 ` Dan Williams [this message]
2020-05-11 15:24 ` Vivek Goyal
2020-04-30 19:51 ` Dan Williams
2020-04-30 20:07 ` Andy Lutomirski
2020-05-01 7:46 ` David Laight
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