From: Jason Gunthorpe <jgg@nvidia.com>
To: Leon Romanovsky <leon@kernel.org>
Cc: "Margolin, Michael" <mrgolin@amazon.com>,
linux-rdma@vger.kernel.org, sleybo@amazon.com, matua@amazon.com,
gal.pressman@linux.dev, Firas Jahjah <firasj@amazon.com>,
Yonatan Nachum <ynachum@amazon.com>
Subject: Re: [PATCH for-next] RDMA/core: Fix best page size finding when it can cross SG entries
Date: Fri, 14 Feb 2025 11:33:40 -0400 [thread overview]
Message-ID: <20250214153340.GG3886819@nvidia.com> (raw)
In-Reply-To: <20250214055511.GQ17863@unreal>
On Fri, Feb 14, 2025 at 07:55:11AM +0200, Leon Romanovsky wrote:
> > The point is to detect cases where they happen to be in order because
> > they were split up due to the 32 bit limit in the sgl.
>
> There is no promise that this split will create consecutive SG entries
> and iterator will fetch them in that order too.
Yes, that is guarenteed, if the memory is contiguous and split then
the SG entries have to be consecutive and the sg iterator has to go in
order.
Otherwise the DMA transfer would be scrambled.
In normal cases we except the SGL to already be fully aggregated so
all SGL boundaries also have a dma_addr discontinuity. This special
case of exceeding the 32 bit limit is the only time we should have
consecutive sgls that are dma_addr contiguous.
Jason
next prev parent reply other threads:[~2025-02-14 15:33 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-09 14:26 [PATCH for-next] RDMA/core: Fix best page size finding when it can cross SG entries Michael Margolin
2025-02-13 12:51 ` Leon Romanovsky
2025-02-13 14:04 ` Jason Gunthorpe
2025-02-13 14:30 ` Margolin, Michael
2025-02-13 14:42 ` Jason Gunthorpe
2025-02-13 17:25 ` Margolin, Michael
2025-02-13 17:35 ` Leon Romanovsky
2025-02-13 17:40 ` Jason Gunthorpe
2025-02-13 17:55 ` Leon Romanovsky
2025-02-13 18:12 ` Jason Gunthorpe
2025-02-14 5:55 ` Leon Romanovsky
2025-02-14 15:33 ` Jason Gunthorpe [this message]
2025-02-16 8:07 ` Leon Romanovsky
2025-02-17 8:40 ` Margolin, Michael
2025-02-13 12:53 ` Leon Romanovsky
2025-02-14 6:57 ` Leon Romanovsky
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