Re: [PATCH V6 8/8] PCI/P2PDMA: Add a 10-bit tag check in P2PDMA

[Dongdong Liu <liudongdong3@huawei.com>]

Hi Logan
Many thanks for your review.
On 2021/7/24 0:25, Logan Gunthorpe wrote:
>
>
>
> On 2021-07-23 5:06 a.m., Dongdong Liu wrote:
>> Add a 10-Bit Tag check in the P2PDMA code to ensure that a device with
>> 10-Bit Tag Requester doesn't interact with a device that does not
>> support 10-BIT tag Completer. Before that happens, the kernel should
>> emit a warning saying to enable a ”pci=disable_10bit_tag=“ kernel
>> parameter.
>>
>> Signed-off-by: Dongdong Liu <liudongdong3@huawei.com>
>> ---
>>  drivers/pci/p2pdma.c | 38 ++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 38 insertions(+)
>>
>> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
>> index 50cdde3..bd93840 100644
>> --- a/drivers/pci/p2pdma.c
>> +++ b/drivers/pci/p2pdma.c
>> @@ -19,6 +19,7 @@
>>  #include <linux/random.h>
>>  #include <linux/seq_buf.h>
>>  #include <linux/xarray.h>
>> +#include "pci.h"
>>
>>  enum pci_p2pdma_map_type {
>>  	PCI_P2PDMA_MAP_UNKNOWN = 0,
>> @@ -541,6 +542,39 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
>>  	return map_type;
>>  }
>>
>> +
>> +static bool check_10bit_tags_vaild(struct pci_dev *a, struct pci_dev *b,
>> +				   bool verbose)
>> +{
>> +	bool req;
>> +	bool comp;
>> +	u16 ctl2;
>> +
>> +	if (a->is_virtfn) {
>> +#ifdef CONFIG_PCI_IOV
>> +		req = !!(a->physfn->sriov->ctrl &
>> +			 PCI_SRIOV_CTRL_VF_10BIT_TAG_REQ_EN);
>> +#endif
>> +	} else {
>> +		pcie_capability_read_word(a, PCI_EXP_DEVCTL2, &ctl2);
>> +		req = !!(ctl2 & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN);
>> +	}
>> +
>> +	comp = !!(b->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_COMP);
>> +	if (req && (!comp)) {
>> +		if (verbose) {
>> +			pci_warn(a, "cannot be used for peer-to-peer DMA as 10-Bit Tag Requester enable is set in device (%s), but peer device (%s) does not support the 10-Bit Tag Completer\n",
>> +				 pci_name(a), pci_name(b));
>> +
>> +			pci_warn(a, "to disable 10-Bit Tag Requester for this device, add the kernel parameter: pci=disable_10bit_tag=%s\n",
>> +				 pci_name(a));
>> +		}
>> +		return false;
>> +	}
>> +
>> +	return true;
>> +}
>> +
>>  /**
>>   * pci_p2pdma_distance_many - Determine the cumulative distance between
>>   *	a p2pdma provider and the clients in use.
>> @@ -579,6 +613,10 @@ int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,
>>  			return -1;
>>  		}
>>
>> +		if (!check_10bit_tags_vaild(pci_client, provider, verbose) ||
>> +		    !check_10bit_tags_vaild(provider, pci_client, verbose))
>> +			not_supported = true;
>> +
>
> This check needs to be done in calc_map_type_and_dist(). The mapping
> type needs to be correctly stored in the xarray cache as other functions
> rely on the cached value (and upcoming work will be calling
> calc_map_type_and_dist() without pci_p2pdma_distance_many()).
>
Will fix.

Thanks,
Dongdong
> Logan
> .
>