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SubjectRe: [PATCH v2] PCI/P2PDMA: Root complex whitelist should not apply when an IOMMU is present
On Wed, Jun 19, 2019 at 12:56:26PM -0600, Logan Gunthorpe wrote:
> Presently, there is no path to DMA map P2PDMA memory, so if a TLP
> targeting this memory hits the root complex and an IOMMU is present,
> the IOMMU will reject the transaction, even if the RC would support
> P2PDMA.
>
> So until the kernel knows to map these DMA addresses in the IOMMU,
> we should not enable the whitelist when an IOMMU is present.
>
> Link: https://lore.kernel.org/linux-pci/20190522201252.2997-1-logang@deltatee.com/
> Fixes: 0f97da831026 ("PCI/P2PDMA: Allow P2P DMA between any devices under AMD ZEN Root Complex")
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Christian König <christian.koenig@amd.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Christoph Hellwig <hch@lst.de>

Applied to for-linus for v5.2, since we merged 0f97da831026 during the v5.2
merge window, thanks!

> ---
> drivers/pci/p2pdma.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index a98126ad9c3a..a4994aa3acc0 100644
> --- a/drivers/pci/p2pdma.c
> +++ b/drivers/pci/p2pdma.c
> @@ -18,6 +18,7 @@
> #include <linux/percpu-refcount.h>
> #include <linux/random.h>
> #include <linux/seq_buf.h>
> +#include <linux/iommu.h>
>
> struct pci_p2pdma {
> struct gen_pool *pool;
> @@ -299,6 +300,9 @@ static bool root_complex_whitelist(struct pci_dev *dev)
> struct pci_dev *root = pci_get_slot(host->bus, PCI_DEVFN(0, 0));
> unsigned short vendor, device;
>
> + if (iommu_present(dev->dev.bus))
> + return false;
> +
> if (!root)
> return false;
>
> --
> 2.20.1
>

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