From: Balbir Singh <bsingharora@gmail.com>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: "Luck, Tony" <tony.luck@intel.com>,
linux-nvdimm <linux-nvdimm@lists.01.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Matthew Wilcox <mawilcox@microsoft.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [RESEND 2/3] powerpc/memcpy: Add memcpy_mcsafe for pmem
Date: Fri, 6 Apr 2018 19:25:52 +1000 [thread overview]
Message-ID: <CAKTCnz=LD_uO7bdwFHDHy9KHHJ_dPA1LdxF1Pm7OUFFGr4s_VA@mail.gmail.com> (raw)
In-Reply-To: <20180406112600.454432f0@roar.ozlabs.ibm.com>
On Fri, Apr 6, 2018 at 11:26 AM, Nicholas Piggin <npiggin@gmail.com> wrote:
> On Thu, 05 Apr 2018 16:40:26 -0400
> Jeff Moyer <jmoyer@redhat.com> wrote:
>
>> Nicholas Piggin <npiggin@gmail.com> writes:
>>
>> > On Thu, 5 Apr 2018 15:53:07 +1000
>> > Balbir Singh <bsingharora@gmail.com> wrote:
>> >> I'm thinking about it, I wonder what "bytes remaining" mean in pmem context
>> >> in the context of a machine check exception. Also, do we want to be byte
>> >> accurate or cache-line accurate for the bytes remaining? The former is much
>> >> easier than the latter :)
>> >
>> > The ideal would be a linear measure of how much of your copy reached
>> > (or can reach) non-volatile storage with nothing further copied. You
>> > may have to allow for some relaxing of the semantics depending on
>> > what the architecture can support.
>>
>> I think you've got that backwards. memcpy_mcsafe is used to copy *from*
>> persistent memory. The idea is to catch errors when reading pmem, not
>> writing to it.
>>
I know the comment in x86 says posted writes and cares for only loads, but I
don't see why both sides should not be handled.
>> > What's the problem with just counting bytes copied like usercopy --
>> > why is that harder than cacheline accuracy?
>>
>> He said the former (i.e. bytes) is easier. So, I think you're on the
>> same page. :)
>
> Oh well that makes a lot more sense in my mind now, thanks :)
I thought the cache-aligned might make sense, since usually we'd expect the
failure to be at a cache-line level, but our copy_tofrom_user does accurate
accounting
Balbir Singh.
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next prev parent reply other threads:[~2018-04-06 9:25 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-04 23:19 [RESEND 0/3] Add support for memcpy_mcsafe Balbir Singh
2018-04-04 23:19 ` [RESEND 1/3] powerpc/mce: Bug fixes for MCE handling in kernel space Balbir Singh
2018-04-04 23:49 ` Nicholas Piggin
2018-04-05 1:11 ` Balbir Singh
2018-04-04 23:19 ` [RESEND 2/3] powerpc/memcpy: Add memcpy_mcsafe for pmem Balbir Singh
2018-04-04 23:57 ` Nicholas Piggin
2018-04-05 3:00 ` Dan Williams
2018-04-05 5:04 ` Nicholas Piggin
2018-04-05 5:53 ` Balbir Singh
2018-04-05 6:45 ` Nicholas Piggin
2018-04-05 15:00 ` Dan Williams
2018-05-01 20:57 ` Dan Williams
2018-05-02 12:36 ` Balbir Singh
2018-04-05 20:40 ` Jeff Moyer
2018-04-06 1:26 ` Nicholas Piggin
2018-04-06 9:25 ` Balbir Singh [this message]
2018-04-06 15:46 ` Luck, Tony
2018-04-04 23:19 ` [RESEND 3/3] powerpc/mce: Handle memcpy_mcsafe Balbir Singh
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