From: Dave Jiang <dave.jiang@intel.com>
To: Borislav Petkov <bp@alien8.de>
Cc: "dmaengine@vger.kernel.org" <dmaengine@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"vkoul@kernel.org" <vkoul@kernel.org>,
"Williams, Dan J" <dan.j.williams@intel.com>,
"Luck, Tony" <tony.luck@intel.com>,
"Lin, Jing" <jing.lin@intel.com>,
"Raj, Ashok" <ashok.raj@intel.com>,
"Kumar, Sanjay K" <sanjay.k.kumar@intel.com>,
"Dey, Megha" <megha.dey@intel.com>,
"Pan, Jacob jun" <jacob.jun.pan@intel.com>,
"Liu, Yi L" <yi.l.liu@intel.com>,
"axboe@kernel.dk" <axboe@kernel.dk>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"Yu, Fenghua" <fenghua.yu@intel.com>,
"hpa@zytor.com" <hpa@zytor.com>
Subject: Re: [PATCH RFC 01/14] x86/asm: add iosubmit_cmds512() based on movdir64b CPU instruction
Date: Wed, 20 Nov 2019 17:10:41 -0700 [thread overview]
Message-ID: <247008b5-6d33-a51b-0caa-7f1991a94dbd@intel.com> (raw)
In-Reply-To: <20191120215338.GN2634@zn.tnic>
On 11/20/19 2:53 PM, Borislav Petkov wrote:
> On Wed, Nov 20, 2019 at 02:23:49PM -0700, Dave Jiang wrote:
>> +/**
>> + * iosubmit_cmds512 - copy data to single MMIO location, in 512-bit units
>
> Where is the alignment check on that data before doing the copying?
I'll add the check on the destination address. The call is modeled after
__iowrite64_copy() / __iowrite32_copy() in lib/iomap_copy.c. Looks like
those functions do not check for the alignment requirements either.
>
>> + * @dst: destination, in MMIO space (must be 512-bit aligned)
>> + * @src: source
>> + * @count: number of 512 bits quantities to submit
>
> Where's that check on the data?
I don't follow?
>
>> + *
>> + * Submit data from kernel space to MMIO space, in units of 512 bits at a
>> + * time. Order of access is not guaranteed, nor is a memory barrier
>> + * performed afterwards.
>> + */
>> +static inline void iosubmit_cmds512(void __iomem *dst, const void *src,
>> + size_t count)
>
> An iosubmit function which returns void and doesn't tell its callers
> whether it succeeded or not? That looks non-optimal to say the least.
>
> Why isn't there a fallback function which to call when the CPU doesn't
> support movdir64b?
>
> Because then you can use alternative_call() and have the thing work
> regardless of hardware support for MOVDIR*.
Looks like Tony answered this part.
>
>> +{
>> + const u8 *from = src;
>> + const u8 *end = from + count * 64;
>> +
>> + if (!cpu_has_write512())
>
> If anything, that thing needs to go and you should use
>
> static_cpu_has(X86_FEATURE_MOVDIR64B)
>
> as it looks to me like you would care about speed on this fast path?
> Yes, no?
>
Yes thank you!
next prev parent reply other threads:[~2019-11-21 0:10 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-20 21:23 [PATCH RFC 00/14] idxd driver for Intel Data Streaming Accelerator Dave Jiang
2019-11-20 21:23 ` [PATCH RFC 01/14] x86/asm: add iosubmit_cmds512() based on movdir64b CPU instruction Dave Jiang
2019-11-20 21:50 ` Dave Hansen
2019-11-20 23:46 ` Dave Jiang
2019-11-20 21:53 ` Borislav Petkov
2019-11-20 23:19 ` Luck, Tony
2019-11-20 23:26 ` Borislav Petkov
2019-11-21 0:15 ` Luck, Tony
2019-11-21 0:27 ` Dan Williams
2019-11-21 0:53 ` Thomas Gleixner
2019-11-21 1:32 ` Dan Williams
2019-11-21 10:37 ` Borislav Petkov
2019-11-21 0:21 ` Dan Williams
2019-11-21 0:22 ` Thomas Gleixner
2019-11-21 0:27 ` Dave Jiang
2019-11-21 0:10 ` Dave Jiang [this message]
2019-11-21 10:59 ` Borislav Petkov
2019-11-21 16:52 ` Dave Jiang
2019-11-22 8:59 ` Borislav Petkov
2019-11-22 17:20 ` Dan Williams
2019-11-22 18:44 ` Borislav Petkov
2019-11-22 18:50 ` Dan Williams
2019-11-20 21:23 ` [PATCH RFC 02/14] dmaengine: break out channel registration Dave Jiang
2019-11-20 21:24 ` [PATCH RFC 03/14] dmaengine: add new dma device registration Dave Jiang
2019-11-20 21:24 ` [PATCH RFC 04/14] mm: create common code from request allocation based from blk-mq code Dave Jiang
2019-11-20 21:24 ` [PATCH RFC 05/14] dmaengine: add dma_request support functions Dave Jiang
2019-11-20 21:24 ` [PATCH RFC 06/14] dmaengine: add dma request submit and completion path support Dave Jiang
2019-11-20 21:24 ` [PATCH RFC 07/14] dmaengine: update dmatest to support dma request Dave Jiang
2019-11-20 21:24 ` [PATCH RFC 08/14] dmaengine: idxd: Init and probe for Intel data accelerators Dave Jiang
2019-11-20 21:24 ` [PATCH RFC 09/14] dmaengine: idxd: add configuration component of driver Dave Jiang
2019-11-20 21:24 ` [PATCH RFC 10/14] dmaengine: idxd: add descriptor manipulation routines Dave Jiang
2019-11-20 21:24 ` [PATCH RFC 11/14] dmaengine: idxd: connect idxd to dmaengine subsystem Dave Jiang
2019-11-20 21:24 ` [PATCH RFC 12/14] dmaengine: request submit optimization Dave Jiang
2019-11-20 21:25 ` [PATCH RFC 13/14] dmaengine: idxd: add char driver to expose submission portal to userland Dave Jiang
2019-11-20 21:25 ` [PATCH RFC 14/14] dmaengine: idxd: add sysfs ABI for idxd driver Dave Jiang
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