linux-kernel - Re: [PATCH v4 1/2] PCI: Add parameter nr_devfns to pci_add_dma

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Date:   Fri, 29 Nov 2019 17:19:42 +0000
From:   James Sewart <jamessewart@...sta.com>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     linux-pci@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Dmitry Safonov <dima@...sta.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Bjorn Helgaas <helgaas@...nel.org>
Subject: Re: [PATCH v4 1/2] PCI: Add parameter nr_devfns to pci_add_dma_alias



> On 29 Nov 2019, at 16:50, Logan Gunthorpe <logang@...tatee.com> wrote:
> 
> 
> 
> On 2019-11-29 5:49 a.m., James Sewart wrote:
>> pci_add_dma_alias can now be used to create a dma alias for a range of
>> devfns.
>> 
>> Signed-off-by: James Sewart <jamessewart@...sta.com>
>> ---
>> drivers/pci/pci.c    | 23 ++++++++++++++++++-----
>> drivers/pci/quirks.c | 14 +++++++-------
>> include/linux/pci.h  |  2 +-
>> 3 files changed, 26 insertions(+), 13 deletions(-)
>> 
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index a97e2571a527..9b0e3481fe17 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -5857,7 +5857,8 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode,
>> /**
>>  * pci_add_dma_alias - Add a DMA devfn alias for a device
>>  * @dev: the PCI device for which alias is added
>> - * @devfn: alias slot and function
>> + * @devfn_from: alias slot and function
>> + * @nr_devfns: Number of subsequent devfns to alias
>>  *
>>  * This helper encodes an 8-bit devfn as a bit number in dma_alias_mask
>>  * which is used to program permissible bus-devfn source addresses for DMA
>> @@ -5873,8 +5874,14 @@ int pci_set_vga_state(struct pci_dev *dev, bool decode,
>>  * cannot be left as a userspace activity).  DMA aliases should therefore
>>  * be configured via quirks, such as the PCI fixup header quirk.
>>  */
>> -void pci_add_dma_alias(struct pci_dev *dev, u8 devfn)
>> +void pci_add_dma_alias(struct pci_dev *dev, u8 devfn_from, unsigned nr_devfns)
>> {
>> +	int devfn_to;
>> +
>> +	if (nr_devfns > U8_MAX+1)
>> +		nr_devfns = U8_MAX+1;
> 
> Why +1? That doesn't seem right to me….

U8_MAX is the max number U8 can represent(255) but is one less than the number 
of values it can represent(256). devfns can be 0.0 to 1f.7 inclusive(I think) 
so the number of possible devfns is 256. Thinking about it, maybe the 
zalloc should be U8_MAX+1 too?

I might be wrong though, what do you reckon?

> 
>> +	devfn_to = devfn_from + nr_devfns - 1;
>> +
>> 	if (!dev->dma_alias_mask)
>> 		dev->dma_alias_mask = bitmap_zalloc(U8_MAX, GFP_KERNEL);
>> 	if (!dev->dma_alias_mask) {
>> @@ -5882,9 +5889,15 @@ void pci_add_dma_alias(struct pci_dev *dev, u8 devfn)
>> 		return;
>> 	}
>> 
>> -	set_bit(devfn, dev->dma_alias_mask);
>> -	pci_info(dev, "Enabling fixed DMA alias to %02x.%d\n",
>> -		 PCI_SLOT(devfn), PCI_FUNC(devfn));
>> +	bitmap_set(dev->dma_alias_mask, devfn_from, nr_devfns);
>> +
>> +	if (nr_devfns == 1)
>> +		pci_info(dev, "Enabling fixed DMA alias to %02x.%d\n",
>> +				PCI_SLOT(devfn_from), PCI_FUNC(devfn_from));
>> +	else if(nr_devfns > 1)
>> +		pci_info(dev, "Enabling fixed DMA alias for devfn range from %02x.%d to %02x.%d\n",
>> +				PCI_SLOT(devfn_from), PCI_FUNC(devfn_from),
>> +				PCI_SLOT(devfn_to), PCI_FUNC(devfn_to));
>> }
>> 
>> bool pci_devs_are_dma_aliases(struct pci_dev *dev1, struct pci_dev *dev2)
>> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
>> index 320255e5e8f8..0f3f5afc73fd 100644
>> --- a/drivers/pci/quirks.c
>> +++ b/drivers/pci/quirks.c
>> @@ -3932,7 +3932,7 @@ int pci_dev_specific_reset(struct pci_dev *dev, int probe)
>> static void quirk_dma_func0_alias(struct pci_dev *dev)
>> {
>> 	if (PCI_FUNC(dev->devfn) != 0)
>> -		pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 0));
>> +		pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 0), 1);
>> }
>> 
>> /*
>> @@ -3946,7 +3946,7 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_RICOH, 0xe476, quirk_dma_func0_alias);
>> static void quirk_dma_func1_alias(struct pci_dev *dev)
>> {
>> 	if (PCI_FUNC(dev->devfn) != 1)
>> -		pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 1));
>> +		pci_add_dma_alias(dev, PCI_DEVFN(PCI_SLOT(dev->devfn), 1), 1);
>> }
>> 
>> /*
>> @@ -4031,7 +4031,7 @@ static void quirk_fixed_dma_alias(struct pci_dev *dev)
>> 
>> 	id = pci_match_id(fixed_dma_alias_tbl, dev);
>> 	if (id)
>> -		pci_add_dma_alias(dev, id->driver_data);
>> +		pci_add_dma_alias(dev, id->driver_data, 1);
>> }
>> 
>> DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ADAPTEC2, 0x0285, quirk_fixed_dma_alias);
>> @@ -4073,9 +4073,9 @@ DECLARE_PCI_FIXUP_HEADER(0x8086, 0x244e, quirk_use_pcie_bridge_dma_alias);
>>  */
>> static void quirk_mic_x200_dma_alias(struct pci_dev *pdev)
>> {
>> -	pci_add_dma_alias(pdev, PCI_DEVFN(0x10, 0x0));
>> -	pci_add_dma_alias(pdev, PCI_DEVFN(0x11, 0x0));
>> -	pci_add_dma_alias(pdev, PCI_DEVFN(0x12, 0x3));
>> +	pci_add_dma_alias(pdev, PCI_DEVFN(0x10, 0x0), 1);
>> +	pci_add_dma_alias(pdev, PCI_DEVFN(0x11, 0x0), 1);
>> +	pci_add_dma_alias(pdev, PCI_DEVFN(0x12, 0x3), 1);
>> }
>> DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2260, quirk_mic_x200_dma_alias);
>> DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2264, quirk_mic_x200_dma_alias);
>> @@ -5273,7 +5273,7 @@ static void quirk_switchtec_ntb_dma_alias(struct pci_dev *pdev)
>> 			pci_dbg(pdev,
>> 				"Aliasing Partition %d Proxy ID %02x.%d\n",
>> 				pp, PCI_SLOT(devfn), PCI_FUNC(devfn));
>> -			pci_add_dma_alias(pdev, devfn);
>> +			pci_add_dma_alias(pdev, devfn, 1);
>> 		}
>> 	}
>> 
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 1a6cf19eac2d..84a8d4c2b24e 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -2323,7 +2323,7 @@ static inline struct eeh_dev *pci_dev_to_eeh_dev(struct pci_dev *pdev)
>> }
>> #endif
>> 
>> -void pci_add_dma_alias(struct pci_dev *dev, u8 devfn);
>> +void pci_add_dma_alias(struct pci_dev *dev, u8 devfn_from, unsigned nr_devfns);
>> bool pci_devs_are_dma_aliases(struct pci_dev *dev1, struct pci_dev *dev2);
>> int pci_for_each_dma_alias(struct pci_dev *pdev,
>> 			   int (*fn)(struct pci_dev *pdev,
>>