linux-kernel - Re: [PATCH] Ensure pci transactions coming from PLX NTB are handled when IOMMU is turned on

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Date:   Wed, 20 Nov 2019 17:48:45 +0000
From:   Dmitry Safonov <0x7f454c46@...il.com>
To:     James Sewart <jamessewart@...sta.com>,
        iommu@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Dmitry Safonov <dima@...sta.com>,
        linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: Re: [PATCH] Ensure pci transactions coming from PLX NTB are handled
 when IOMMU is turned on

+Cc: linux-pci@...r.kernel.org
+Cc: Bjorn Helgaas <bhelgaas@...gle.com>
+Cc: Logan Gunthorpe <logang@...tatee.com>

On 11/5/19 12:17 PM, James Sewart wrote:
> Any comments on this?
> 
> Cheers,
> James.
> 
>> On 24 Oct 2019, at 13:52, James Sewart <jamessewart@...sta.com> wrote:
>>
>> The PLX PEX NTB forwards DMA transactions using Requester ID's that don't exist as
>> PCI devices. The devfn for a transaction is used as an index into a lookup table
>> storing the origin of a transaction on the other side of the bridge.
>>
>> This patch aliases all possible devfn's to the NTB device so that any transaction
>> coming in is governed by the mappings for the NTB.
>>
>> Signed-Off-By: James Sewart <jamessewart@...sta.com>
>> ---
>> drivers/pci/quirks.c | 22 ++++++++++++++++++++++
>> 1 file changed, 22 insertions(+)
>>
>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
>> index 320255e5e8f8..647f546e427f 100644
>> --- a/drivers/pci/quirks.c
>> +++ b/drivers/pci/quirks.c
>> @@ -5315,6 +5315,28 @@ SWITCHTEC_QUIRK(0x8574);  /* PFXI 64XG3 */
>> SWITCHTEC_QUIRK(0x8575);  /* PFXI 80XG3 */
>> SWITCHTEC_QUIRK(0x8576);  /* PFXI 96XG3 */
>>
>> +/*
>> + * PLX NTB uses devfn proxy IDs to move TLPs between NT endpoints. These IDs
>> + * are used to forward responses to the originator on the other side of the
>> + * NTB. Alias all possible IDs to the NTB to permit access when the IOMMU is
>> + * turned on.
>> + */
>> +static void quirk_PLX_NTB_dma_alias(struct pci_dev *pdev)
>> +{
>> +	if (!pdev->dma_alias_mask)
>> +		pdev->dma_alias_mask = kcalloc(BITS_TO_LONGS(U8_MAX),
>> +					      sizeof(long), GFP_KERNEL);
>> +	if (!pdev->dma_alias_mask) {
>> +		dev_warn(&pdev->dev, "Unable to allocate DMA alias mask\n");
>> +		return;
>> +	}
>> +
>> +	// PLX NTB may use all 256 devfns
>> +	memset(pdev->dma_alias_mask, U8_MAX, (U8_MAX+1)/BITS_PER_BYTE);
>> +}
>> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_PLX, 0x87b0, quirk_PLX_NTB_dma_alias);
>> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_PLX, 0x87b1, quirk_PLX_NTB_dma_alias);
>> +
>> /*
>>  * On Lenovo Thinkpad P50 SKUs with a Nvidia Quadro M1000M, the BIOS does
>>  * not always reset the secondary Nvidia GPU between reboots if the system
>> -- 
>> 2.19.1
>>
>>
> 

Thanks,
          Dmitry