Re: [PATCH v3 02/10] iommu/vt-d: Extend dmar_domain to support nested domain

[Baolu Lu]

On 5/24/23 3:02 PM, Tian, Kevin wrote:
> > From: Liu, Yi L<yi.l.liu@xxxxxxxxx>
> > Sent: Thursday, May 11, 2023 10:51 PM
> >
> > From: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> >
> > The nested domain fields are exclusive to those that used for a DMA
> > remapping domain. Use union to avoid memory waste.
> >
> > Signed-off-by: Lu Baolu<baolu.lu@xxxxxxxxxxxxxxx>
> > Signed-off-by: Yi Liu<yi.l.liu@xxxxxxxxx>
> > ---
> >   drivers/iommu/intel/iommu.h | 35 +++++++++++++++++++++++++++++------
> >   1 file changed, 29 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
> > index 1c5e1d88862b..e818520f4068 100644
> > --- a/drivers/iommu/intel/iommu.h
> > +++ b/drivers/iommu/intel/iommu.h
> > @@ -596,15 +596,38 @@ struct dmar_domain {
> >   	spinlock_t lock;		/* Protect device tracking lists */
> >   	struct list_head devices;	/* all devices' list */
> >
> > -	struct dma_pte	*pgd;		/* virtual address */
> > -	int		gaw;		/* max guest address width */
> > -
> > -	/* adjusted guest address width, 0 is level 2 30-bit */
> > -	int		agaw;
> >   	int		iommu_superpage;/* Level of superpages supported:
> >   					   0 == 4KiB (no superpages), 1 ==
> > 2MiB,
> >   					   2 == 1GiB, 3 == 512GiB, 4 == 1TiB */
> > -	u64		max_addr;	/* maximum mapped address */
> > +	union {
> > +		/* DMA remapping domain */
> > +		struct {
> > +			/* virtual address */
> > +			struct dma_pte	*pgd;
> > +			/* max guest address width */
> > +			int		gaw;
> > +			/*
> > +			 * adjusted guest address width:
> > +			 *   0: level 2 30-bit
> > +			 *   1: level 3 39-bit
> > +			 *   2: level 4 48-bit
> > +			 *   3: level 5 57-bit
> > +			 */
> > +			int		agaw;
> > +			/* maximum mapped address */
> > +			u64		max_addr;
> > +		};
> what about 'nid'?


"nid" represents which NUMA node should we allocate pages from for this
domain. It's updated every time when a domain is attached/detached
to/from a device or pasid.

Generally speaking, "nid" is common for all types of domain. But in this
case, only a DMA remapping domain has a need to allocate pages. I intend
to keep it as it for now. There's more cleanup rooms if we limit it only
for DMA remapping domain.

Best regards,
baolu