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SubjectRe: [PATCH V2] PCI/MSI: Set device flag indicating only 32-bit MSI support
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On 12/3/2020 11:54 PM, Bjorn Helgaas wrote:
> External email: Use caution opening links or attachments
>
>
> On Tue, Nov 24, 2020 at 04:20:35PM +0530, Vidya Sagar wrote:
>> There are devices (Ex:- Marvell SATA controller) that don't support
>> 64-bit MSIs and the same is advertised through their MSI capability
>> register. Set no_64bit_msi flag explicitly for such devices in the
>> MSI setup code so that the msi_verify_entries() API would catch
>> if the MSI arch code tries to use 64-bit MSI.
>
> This seems good to me. I'll post a possible revision to set
> dev->no_64bit_msi in the device enumeration path instead of in the IRQ
> allocation path, since it's really a property of the device, not of
> the msi_desc.
>
> I like the extra checking this gives us. Was this prompted by
> tripping over something, or is it something you noticed by code
> reading? If the former, a hint about what was wrong and how it's
> being fixed would be useful.
I observed functionality issue with Marvell SATA controller (1b4b:9171)
when the allocated MSI target address was a 64-bit address. I mentioned
the Marvell SATA controller as an example in the commit message.

Thanks,
Vidya Sagar

>
>> Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
>> ---
>> V2:
>> * Addressed Bjorn's comment and changed the error message
>>
>> drivers/pci/msi.c | 11 +++++++----
>> 1 file changed, 7 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
>> index d52d118979a6..8de5ba6b4a59 100644
>> --- a/drivers/pci/msi.c
>> +++ b/drivers/pci/msi.c
>> @@ -581,10 +581,12 @@ msi_setup_entry(struct pci_dev *dev, int nvec, struct irq_affinity *affd)
>> entry->msi_attrib.multi_cap = (control & PCI_MSI_FLAGS_QMASK) >> 1;
>> entry->msi_attrib.multiple = ilog2(__roundup_pow_of_two(nvec));
>>
>> - if (control & PCI_MSI_FLAGS_64BIT)
>> + if (control & PCI_MSI_FLAGS_64BIT) {
>> entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_64;
>> - else
>> + } else {
>> entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_32;
>> + dev->no_64bit_msi = 1;
>> + }
>>
>> /* Save the initial mask status */
>> if (entry->msi_attrib.maskbit)
>> @@ -602,8 +604,9 @@ static int msi_verify_entries(struct pci_dev *dev)
>> for_each_pci_msi_entry(entry, dev) {
>> if (!dev->no_64bit_msi || !entry->msg.address_hi)
>> continue;
>> - pci_err(dev, "Device has broken 64-bit MSI but arch"
>> - " tried to assign one above 4G\n");
>> + pci_err(dev, "Device has either broken 64-bit MSI or "
>> + "only 32-bit MSI support but "
>> + "arch tried to assign one above 4G\n");
>> return -EIO;
>> }
>> return 0;
>> --
>> 2.17.1
>>

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