Re: [PATCH] PCI: vmd: Assign vmd irq domain before enumeration

["Patel, Nirmal" <nirmal.patel@linux.intel.com>]

On 3/2/2022 1:55 PM, Bjorn Helgaas wrote:
> On Wed, Mar 02, 2022 at 12:35:20PM -0700, Jonathan Derrick wrote:
>> Hey Nirmal,
>>
>> Sorry I didn't catch this earlier.
>>
>> On 3/2/2022 10:41 AM, Patel, Nirmal wrote:
>>> On 2/23/2022 12:52 AM, Nirmal Patel wrote:
>>>> vmd creates and assigns separate irq domain only when MSI remapping is
>>>> enabled. For example VMD-MSI. But vmd doesn't assign irq domain when
>>>> MSI remapping is disabled resulting child devices getting default
>>>> PCI-MSI irq domain. Now when Interrupt remapping is enabled all the
>>>> pci devices are assigned INTEL-IR-MSI domain including vmd endpoints.
>>>> But devices behind vmd gets PCI-MSI irq domain when vmd creates root
>>>> bus and configures child devices.
>> can you capitalize VMD for consistency?
> And IRQ, while you're at it.  Both occur several times above (and
> below).  And PCI.
>
> Also, s/Interrupt remapping/interrupt remapping/ above, since
> there's no reason to capitalize "Interrupt" there.
>
> s/behind vmd gets/behind VMD get/
Understood.
>
>>>> As a result DMAR errors were observed when interrupt remapping was
>>>> enabled on Intel Icelake CPUs.
>>>> For instance:
>>>> DMAR: DRHD: handling fault status reg 2
>>>> DMAR: [INTR-REMAP] Request device [0xe2:0x00.0] fault index 0xa00
>>>> [fault reason 0x25] Blocked a compatibility format interrupt request
> Quote material as in 2565e5b69c44, e.g.,
>
>   As a result DMAR errors were observed ...  For instance:
>
>     DMAR: DRHD: handling fault status reg 2
>     DMAR: [INTR-REMAP] Request device [0xe2:0x00.0] fault index 0xa00 [fault reason 0x25] Blocked a compatibility format interrupt request
>
> (Blank line before and after quoted material, indent quote two spaces,
> don't break messages over lines, so they're easy to grep for.)
>
>>>> So make sure vmd assigns proper irq domain. This patch also removes
>>>> a placeholder patch 2565e5b69c44 (PCI: vmd: Do not disable MSI-X
>>>> remapping if interrupt remapping is enabled by IOMMU.)
> Usual commit citation style is
>
>   2565e5b69c44 ("PCI: vmd: Do not disable MSI-X remapping if interrupt
>   remapping is enabled by IOMMU")
>
> Why is this revert part of this patch?  Could it be a separate patch?
> Either way, we should explain why we can now revert it.
I will add some more details.
>
>>>> MSI remapping
>>>> should be enabled or disabled with and without Interrupt remap.
>>>>
>> So this keeps the performance path working with remapping?
>> Great!
>>
>>
>>>> Signed-off-by: Nirmal Patel <nirmal.patel@linux.intel.com>
>>>> ---
>>>>   drivers/pci/controller/vmd.c | 7 ++++---
>>>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
>>>> index cc166c683638..c8d73d75a1c0 100644
>>>> --- a/drivers/pci/controller/vmd.c
>>>> +++ b/drivers/pci/controller/vmd.c
>>>> @@ -813,8 +813,7 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>>>>   	 * acceptable because the guest is usually CPU-limited and MSI
>>>>   	 * remapping doesn't become a performance bottleneck.
>>>>   	 */
>>>> -	if (iommu_capable(vmd->dev->dev.bus, IOMMU_CAP_INTR_REMAP) ||
>>>> -	    !(features & VMD_FEAT_CAN_BYPASS_MSI_REMAP) ||
>>>> +	if (!(features & VMD_FEAT_CAN_BYPASS_MSI_REMAP) ||
>>>>   	    offset[0] || offset[1]) {
>>>>   		ret = vmd_alloc_irqs(vmd);
>>>>   		if (ret)
>>>> @@ -853,7 +852,9 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>>>>   	vmd_attach_resources(vmd);
>>>>   	if (vmd->irq_domain)
>>>>   		dev_set_msi_domain(&vmd->bus->dev, vmd->irq_domain);
>>>> -
>>>> +	else
>>>> +		dev_set_msi_domain(&vmd->bus->dev, vmd->dev->dev.msi.domain);
>> how about dev_get_msi_domain(vmd->dev) ?
Good idea.
>>
>>>> +	
>>>>   	vmd_acpi_begin();
>>>>   	pci_scan_child_bus(vmd->bus);
>>> Gentle ping!
>>>
>>> Thanks
>>>
>>> nirmal
>>>