From: Christoph Hellwig <hch@infradead.org>
To: Sathya Prakash Veerichetty <sathya.prakash@broadcom.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Ranjan Kumar <ranjan.kumar@broadcom.com>,
linux-scsi@vger.kernel.org, martin.petersen@oracle.com
Subject: Re: [PATCH v1] mpt3sas: Set DMA_BIDIRECTIONAL for additional SCSI commands
Date: Tue, 22 Jul 2025 23:26:42 -0700 [thread overview]
Message-ID: <aICAoqAYPsy2ErLg@infradead.org> (raw)
In-Reply-To: <CAFdVvOx2RCtwc2H-K=QOQ+fG2=5s-TN4oOd0qJsCXvzfOpM69g@mail.gmail.com>
On Tue, Jul 22, 2025 at 09:06:10AM -0600, Sathya Prakash Veerichetty wrote:
> There is a resource issue which prevents SATL from doing double
> buffering and RMW of the contents to map the data from SATA drives to
> the host buffers for the specific commands. Our firmware changes
> leads to performance and functional issues, So we are left with either
> failing those commands in the driver or changing the mapping, We
> decided to go with changing the DMA mapping as we know those commands
> require both read/write access to the buffers.
> Any functional issue of changing the DMA mapping?
Well, we have to change the mapping to make your broken hardware work.
But these kinds of hacks in firmware are really problematic. When an
application does a passthrough of a SCSI command it can very much
expect that the payload is not changed by a call to SG_IO, and this
breaks it.
next prev parent reply other threads:[~2025-07-23 6:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-21 11:05 [PATCH v1] mpt3sas: Set DMA_BIDIRECTIONAL for additional SCSI commands Ranjan Kumar
2025-07-21 11:42 ` Johannes Thumshirn
2025-07-22 5:57 ` Christoph Hellwig
2025-07-22 15:06 ` Sathya Prakash Veerichetty
2025-07-23 6:26 ` Christoph Hellwig [this message]
2025-07-31 17:51 ` Sathya Prakash Veerichetty
2025-08-01 1:28 ` Damien Le Moal
2026-01-09 23:44 ` Sathya Prakash Veerichetty
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