linux-kernel - Re: [PATCH v4 04/14] PCI/P2PDMA: Clear ACS P2P flags for all devices behind switches

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Date:   Mon, 23 Apr 2018 20:33:47 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-rdma@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-block@...r.kernel.org
Cc:     Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        Keith Busch <keith.busch@...el.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Christian König <christian.koenig@....com>
Subject: Re: [PATCH v4 04/14] PCI/P2PDMA: Clear ACS P2P flags for all devices
 behind switches

On 04/23/2018 04:30 PM, Logan Gunthorpe wrote:> > Signed-off-by: Logan Gunthorpe <logang@...tatee.com>> ---
>  drivers/pci/Kconfig        |  9 +++++++++>  drivers/pci/p2pdma.c       | 45 ++++++++++++++++++++++++++++++--------------->  drivers/pci/pci.c          |  6 ++++++>  include/linux/pci-p2pdma.h |  5 +++++>  4 files changed, 50 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
> index b2396c22b53e..b6db41d4b708 100644
> --- a/drivers/pci/Kconfig
> +++ b/drivers/pci/Kconfig
> @@ -139,6 +139,15 @@ config PCI_P2PDMA
>  	  transations must be between devices behind the same root port.
>  	  (Typically behind a network of PCIe switches).
>  
> +	  Enabling this option will also disable ACS on all ports behind
> +	  any PCIe switch. This effectively puts all devices behind any
> +	  switch heirarchy into the same IOMMU group. Which implies that

	         hierarchy                     group, which

and sames fixes in the commit description...

> +	  individual devices behind any switch will not be able to be
> +	  assigned to separate VMs because there is no isolation between
> +	  them. Additionally, any malicious PCIe devices will be able to
> +	  DMA to memory exposed by other EPs in the same domain as TLPs
> +	  will not be checked by the IOMMU.
> +
>  	  If unsure, say N.
>  
>  config PCI_LABEL


-- 
~Randy