linux-kernel - Re: [PATCH 06/14] PCI/P2PDMA: Add whitelist support for Intel Host Bridges

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Message-ID: <20190725185230.GG7450@mellanox.com>
Date:   Thu, 25 Jul 2019 18:52:36 +0000
From:   Jason Gunthorpe <jgg@...lanox.com>
To:     Logan Gunthorpe <logang@...tatee.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Christoph Hellwig <hch@....de>,
        Christian Koenig <Christian.Koenig@....com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Dan Williams <dan.j.williams@...el.com>,
        Eric Pilmore <epilmore@...aio.com>,
        Stephen Bates <sbates@...thlin.com>
Subject: Re: [PATCH 06/14] PCI/P2PDMA: Add whitelist support for Intel Host
 Bridges

On Mon, Jul 22, 2019 at 05:08:51PM -0600, Logan Gunthorpe wrote:
> Intel devices do not have good support for P2P requests that span
> different host bridges as the transactions will cross the QPI/UPI bus
> and this does not perform well.
> 
> Therefore, enable support for these devices only if the host bridges
> match.
> 
> Adds the Intel device's that have been tested to work. There are
> likely many others out there that will need to be tested and added.
> 
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
>  drivers/pci/p2pdma.c | 36 ++++++++++++++++++++++++++++++++----
>  1 file changed, 32 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index dfb802afc8ca..143e11d2a5c3 100644
> +++ b/drivers/pci/p2pdma.c
> @@ -250,9 +250,28 @@ static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)
>  	seq_buf_printf(buf, "%s;", pci_name(pdev));
>  }
>  
> -static bool __host_bridge_whitelist(struct pci_host_bridge *host)
> +static const struct pci_p2pdma_whitelist_entry {
> +	unsigned short vendor;
> +	unsigned short device;
> +	bool req_same_host_bridge;

This would be more readable in the initializer as a flags not a bool

Jason