From: Dan Williams <dan.j.williams@intel.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tony Luck <tony.luck@intel.com>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
Peter Zijlstra <peterz@infradead.org>,
the arch/x86 maintainers <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@amacapital.net>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Al Viro <viro@zeniv.linux.org.uk>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 0/6] use memcpy_mcsafe() for copy_to_iter()
Date: Tue, 1 May 2018 20:20:49 -0700 [thread overview]
Message-ID: <CAPcyv4hQVKL=OtoYbWDGfOMdWen3MkF5qBPrek98+w2gODHvtg@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFzDt1uvDBqgkB0T2o2-d5Fi0tBiGcy5iAZ-wRNdAL4uQw@mail.gmail.com>
On Tue, May 1, 2018 at 8:13 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Tue, May 1, 2018 at 8:03 PM Dan Williams <dan.j.williams@intel.com>
> wrote:
>
>> Because dax. There's no page cache indirection games we can play here
>> to poison a page and map in another page. The mapped page is 1:1
>> associated with the filesystem block and physical memory address.
>
> I'm not talking page cache indirection.
>
> I'm talking literally mapping a different page into the kernel virtual
> address space that the failing read was done for.
>
> But you seem to be right that we don't actually support that. I'm guessing
> the hwpoison code has never had to run in that kind of situation and will
> just give up.
>
> That would seem to be sad. It really feels like the obvious solution to any
> MCE's - just map a dummy page at the address that causes problems.
>
> That can have bad effects for real memory (because who knows what internal
> kernel data structure might be in there), but would seem to be the
> _optimal_ solution for some random pmem access. And makes it absolutely
> trivial to just return to the execution that got the error exception.
The other property of pmem that we need to contend with that makes it
a snowflake relative to typical memory is that errors can be repaired
by sending a slow-path command to the DIMM device. We trap block-layer
writes in the pmem driver that target known 'badblocks' and send the
sideband command to clear the error along with the new data.
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Linux-nvdimm@lists.01.org
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WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams@intel.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
Tony Luck <tony.luck@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>,
"the arch/x86 maintainers" <x86@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andy Lutomirski <luto@amacapital.net>,
Ingo Molnar <mingo@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/6] use memcpy_mcsafe() for copy_to_iter()
Date: Tue, 1 May 2018 20:20:49 -0700 [thread overview]
Message-ID: <CAPcyv4hQVKL=OtoYbWDGfOMdWen3MkF5qBPrek98+w2gODHvtg@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFzDt1uvDBqgkB0T2o2-d5Fi0tBiGcy5iAZ-wRNdAL4uQw@mail.gmail.com>
On Tue, May 1, 2018 at 8:13 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Tue, May 1, 2018 at 8:03 PM Dan Williams <dan.j.williams@intel.com>
> wrote:
>
>> Because dax. There's no page cache indirection games we can play here
>> to poison a page and map in another page. The mapped page is 1:1
>> associated with the filesystem block and physical memory address.
>
> I'm not talking page cache indirection.
>
> I'm talking literally mapping a different page into the kernel virtual
> address space that the failing read was done for.
>
> But you seem to be right that we don't actually support that. I'm guessing
> the hwpoison code has never had to run in that kind of situation and will
> just give up.
>
> That would seem to be sad. It really feels like the obvious solution to any
> MCE's - just map a dummy page at the address that causes problems.
>
> That can have bad effects for real memory (because who knows what internal
> kernel data structure might be in there), but would seem to be the
> _optimal_ solution for some random pmem access. And makes it absolutely
> trivial to just return to the execution that got the error exception.
The other property of pmem that we need to contend with that makes it
a snowflake relative to typical memory is that errors can be repaired
by sending a slow-path command to the DIMM device. We trap block-layer
writes in the pmem driver that target known 'badblocks' and send the
sideband command to clear the error along with the new data.
next prev parent reply other threads:[~2018-05-02 3:20 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-01 20:45 [PATCH 0/6] use memcpy_mcsafe() for copy_to_iter() Dan Williams
2018-05-01 20:45 ` Dan Williams
2018-05-01 20:45 ` [PATCH 1/6] x86, memcpy_mcsafe: update labels in support of write fault handling Dan Williams
2018-05-01 20:45 ` Dan Williams
2018-05-01 20:45 ` [PATCH 2/6] x86, memcpy_mcsafe: return bytes remaining Dan Williams
2018-05-01 20:45 ` Dan Williams
2018-05-01 20:45 ` [PATCH 3/6] x86, memcpy_mcsafe: add write-protection-fault handling Dan Williams
2018-05-01 20:45 ` Dan Williams
2018-05-01 20:45 ` [PATCH 4/6] x86, memcpy_mcsafe: define copy_to_iter_mcsafe() Dan Williams
2018-05-01 20:45 ` Dan Williams
2018-05-01 22:17 ` kbuild test robot
2018-05-01 22:17 ` kbuild test robot
2018-05-01 22:49 ` kbuild test robot
2018-05-01 22:49 ` kbuild test robot
2018-05-01 20:45 ` [PATCH 5/6] dax: use copy_to_iter_mcsafe() in dax_iomap_actor() Dan Williams
2018-05-01 20:45 ` Dan Williams
2018-05-01 20:45 ` [PATCH 6/6] x86, nfit_test: unit test for memcpy_mcsafe() Dan Williams
2018-05-01 20:45 ` Dan Williams
2018-05-01 21:05 ` [PATCH 0/6] use memcpy_mcsafe() for copy_to_iter() Linus Torvalds
2018-05-01 21:05 ` Linus Torvalds
2018-05-01 23:02 ` Dan Williams
2018-05-01 23:02 ` Dan Williams
2018-05-01 23:28 ` Andy Lutomirski
2018-05-01 23:28 ` Andy Lutomirski
2018-05-01 23:31 ` Dan Williams
2018-05-01 23:31 ` Dan Williams
2018-05-02 0:09 ` Linus Torvalds
2018-05-02 0:09 ` Linus Torvalds
2018-05-02 2:25 ` Dan Williams
2018-05-02 2:25 ` Dan Williams
2018-05-02 2:53 ` Linus Torvalds
2018-05-02 2:53 ` Linus Torvalds
2018-05-02 3:02 ` Dan Williams
2018-05-02 3:02 ` Dan Williams
2018-05-02 3:13 ` Linus Torvalds
2018-05-02 3:13 ` Linus Torvalds
2018-05-02 3:20 ` Dan Williams [this message]
2018-05-02 3:20 ` Dan Williams
2018-05-02 3:22 ` Dan Williams
2018-05-02 3:22 ` Dan Williams
2018-05-02 3:33 ` Linus Torvalds
2018-05-02 3:33 ` Linus Torvalds
2018-05-02 4:00 ` Dan Williams
2018-05-02 4:00 ` Dan Williams
2018-05-02 4:14 ` Linus Torvalds
2018-05-02 4:14 ` Linus Torvalds
2018-05-02 5:37 ` Dan Williams
2018-05-02 5:37 ` Dan Williams
2018-05-02 16:19 ` Andy Lutomirski
2018-05-02 16:19 ` Andy Lutomirski
2018-05-02 17:47 ` Dan Williams
2018-05-02 17:47 ` Dan Williams
2018-05-02 8:30 ` Borislav Petkov
2018-05-02 8:30 ` Borislav Petkov
2018-05-02 13:52 ` Dan Williams
2018-05-02 13:52 ` Dan Williams
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