Re: [PATCH v10 04/16] iommu: Cleanup iopf data structure definitions

[Baolu Lu]

On 2024/1/25 18:23, Joel Granados wrote:
> > diff --git a/drivers/iommu/io-pgfault.c b/drivers/iommu/io-pgfault.c
> > index e5b8b9110c13..24b5545352ae 100644
> > --- a/drivers/iommu/io-pgfault.c
> > +++ b/drivers/iommu/io-pgfault.c
> > @@ -56,7 +56,6 @@ static int iopf_complete_group(struct device *dev, struct iopf_fault *iopf,
> >   			       enum iommu_page_response_code status)
> >   {
> >   	struct iommu_page_response resp = {
> > -		.version		= IOMMU_PAGE_RESP_VERSION_1,
> >   		.pasid			= iopf->fault.prm.pasid,
> >   		.grpid			= iopf->fault.prm.grpid,
> >   		.code			= status,
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index 68e648b55767..b88dc3e0595c 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -1494,10 +1494,6 @@ int iommu_page_response(struct device *dev,
> >   	if (!param || !param->fault_param)
> >   		return -EINVAL;
> >   
> > -	if (msg->version != IOMMU_PAGE_RESP_VERSION_1 ||
> > -	    msg->flags & ~IOMMU_PAGE_RESP_PASID_VALID)
> > -		return -EINVAL;
> > -
> I see that this function `iommu_page_response` eventually lands in
> drivers/iommu/io-pgfault.c as `iopf_group_response`. But it seems that
> the check for IOMMU_PAGE_RESP_PASID_VALID is dropped.
>
> I see that after applying [1] and [2] there are only three places where
> IOMMU_PAGE_RESP_PASID_VALID appears in the code: One is the definition
> and the other two are just setting the value. We effectively dropped the

Yes, really. Thanks for pointing this out.

$ git grep IOMMU_PAGE_RESP_PASID_VALID
drivers/iommu/io-pgfault.c:             resp.flags = 
IOMMU_PAGE_RESP_PASID_VALID;
drivers/iommu/io-pgfault.c:                     resp.flags = 
IOMMU_PAGE_RESP_PASID_VALID;
include/linux/iommu.h:#define IOMMU_PAGE_RESP_PASID_VALID       (1 << 0)

> check. Is the drop intended? and if so, should we just get rid of
> IOMMU_PAGE_RESP_PASID_VALID?

In my opinion, we should keep this hardware detail in the individual
driver. When the page fault handling framework in IOMMU and IOMMUFD
subsystems includes a valid PASID in the fault message, the response
message should also contain the *same* PASID value. Individual drivers
should be responsible for deciding whether to include the PASID in the
messages they provide for the hardware.

> Best
>
> [1]https://lore.kernel.org/all/20240122054308.23901-1-baolu.lu@xxxxxxxxxxxxxxx
> [2]https://lore.kernel.org/all/20240122073903.24406-1-baolu.lu@xxxxxxxxxxxxxxx

Best regards,
baolu