RE: [PATCH v5 1/8] ACPI/IORT: Add support for RMR node parsing

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

Hi Robin,

> -----Original Message-----
> From: Robin Murphy [mailto:robin.murphy@arm.com]
> Sent: 14 June 2021 12:15
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>;
> linux-arm-kernel@lists.infradead.org; linux-acpi@vger.kernel.org;
> iommu@lists.linux-foundation.org
> Cc: Linuxarm <linuxarm@huawei.com>; lorenzo.pieralisi@arm.com;
> joro@8bytes.org; wanghuiqiang <wanghuiqiang@huawei.com>; Guohanjun
> (Hanjun Guo) <guohanjun@huawei.com>; steven.price@arm.com;
> Sami.Mujawar@arm.com; jon@solid-run.com; eric.auger@redhat.com;
> yangyicong <yangyicong@huawei.com>
> Subject: Re: [PATCH v5 1/8] ACPI/IORT: Add support for RMR node parsing
> 
> On 2021-05-24 12:02, Shameer Kolothum wrote:
> > Add support for parsing RMR node information from ACPI.
> > Find associated stream id and smmu node info from the
> > RMR node and populate a linked list with RMR memory
> > descriptors.
> >
> > Signed-off-by: Shameer Kolothum
> <shameerali.kolothum.thodi@huawei.com>
> > ---
> >   drivers/acpi/arm64/iort.c | 104
> +++++++++++++++++++++++++++++++++++++-
> >   1 file changed, 103 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> > index 3912a1f6058e..fea1ffaedf3b 100644
> > --- a/drivers/acpi/arm64/iort.c
> > +++ b/drivers/acpi/arm64/iort.c
> > @@ -40,6 +40,19 @@ struct iort_fwnode {
> >   static LIST_HEAD(iort_fwnode_list);
> >   static DEFINE_SPINLOCK(iort_fwnode_lock);
> >
> > +/*
> > + * One entry for IORT RMR.
> > + */
> > +struct iort_rmr_entry {
> > +	struct list_head list;
> > +	u32 sid;
> > +	struct acpi_iort_node *smmu;
> > +	struct acpi_iort_rmr_desc *rmr_desc;
> > +	u32 flags;
> > +};
> > +
> > +static LIST_HEAD(iort_rmr_list);         /* list of RMR regions from ACPI
> */
> > +
> >   /**
> >    * iort_set_fwnode() - Create iort_fwnode and use it to register
> >    *		       iommu data in the iort_fwnode_list
> > @@ -393,7 +406,8 @@ static struct acpi_iort_node
> *iort_node_get_id(struct acpi_iort_node *node,
> >   		if (node->type == ACPI_IORT_NODE_NAMED_COMPONENT ||
> >   		    node->type == ACPI_IORT_NODE_PCI_ROOT_COMPLEX ||
> >   		    node->type == ACPI_IORT_NODE_SMMU_V3 ||
> > -		    node->type == ACPI_IORT_NODE_PMCG) {
> > +		    node->type == ACPI_IORT_NODE_PMCG ||
> > +		    node->type == ACPI_IORT_NODE_RMR) {
> >   			*id_out = map->output_base;
> >   			return parent;
> >   		}
> > @@ -1660,6 +1674,91 @@ static void __init iort_enable_acs(struct
> acpi_iort_node *iort_node)
> >   #else
> >   static inline void iort_enable_acs(struct acpi_iort_node *iort_node) { }
> >   #endif
> > +static int iort_rmr_desc_valid(struct acpi_iort_rmr_desc *desc, u32 count)
> > +{
> > +	int i, j;
> > +
> > +	for (i = 0; i < count; i++) {
> > +		u64 end, start = desc[i].base_address, length = desc[i].length;
> > +
> > +		if (!IS_ALIGNED(start, SZ_64K) || !IS_ALIGNED(length, SZ_64K))
> > +			return -EINVAL;
> 
> We should certainly FW_BUG for this, but maybe it's OK to continue,
> since all we should need to do is round our iommu_resv_regions to at
> least PAGE_SIZE. That seems possibly better than ignoring them and
> having things potentially blow up later (especially if an end user
> exercises the system more thoroughly than the firmware developer tested
> it, which in at least one case I've seen may be "at all"...)

Ok. Will report FW_BUG but continue with a rounded addr/size.

> 
> > +		end = start + length - 1;
> > +
> > +		/* Check for address overlap */
> > +		for (j = i + 1; j < count; j++) {
> > +			u64 e_start = desc[j].base_address;
> > +			u64 e_end = e_start + desc[j].length - 1;
> > +
> > +			if (start <= e_end && end >= e_start)
> > +				return -EINVAL;
> 
> Similarly it's not *too* hard to trim overlaps; I guess it's really a
> question of whether we want to bother :/

I guess then, we can just report it and ignore,
   pr_warn(FW_BUG, "Found overlapping rmr desc @...., but ignoring...\n"

Thanks
Shameer

> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int __init iort_parse_rmr(struct acpi_iort_node *iort_node)
> > +{
> > +	struct acpi_iort_node *smmu;
> > +	struct iort_rmr_entry *e;
> > +	struct acpi_iort_rmr *rmr;
> > +	struct acpi_iort_rmr_desc *rmr_desc;
> > +	u32 map_count = iort_node->mapping_count;
> > +	u32  sid;
> 
> Nit: extra space.
> 
> > +	int i, ret = 0;
> > +
> > +	if (iort_node->type != ACPI_IORT_NODE_RMR)
> > +		return 0;
> > +
> > +	if (!iort_node->mapping_offset || map_count != 1) {
> 
> Beware that there was some discussion about allowing multiple SIDs to
> share an RMR descriptor, since there are potential use-cases which would
> otherwise lead to excessive duplication (e.g. an MSI doorbell carveout
> in a VM which would effectively apply to all possible PCI RIDs). I think
> the conclusion we reached was that disallowing that was fairly
> arbitrary, and could possibly be relaxed in future. It looks like the
> design of things here could grow to fit that fairly easily though, so I
> don't think it's a major concern.
> 
> Robin.
> 
> > +		pr_err(FW_BUG "Invalid ID mapping, skipping RMR node %p\n",
> > +		       iort_node);
> > +		return -EINVAL;
> > +	}
> > +
> > +	/* Retrieve associated smmu and stream id */
> > +	smmu = iort_node_get_id(iort_node, &sid, 0);
> > +	if (!smmu) {
> > +		pr_err(FW_BUG "Invalid SMMU reference, skipping RMR
> node %p\n",
> > +		       iort_node);
> > +		return -EINVAL;
> > +	}
> > +
> > +	/* Retrieve RMR data */
> > +	rmr = (struct acpi_iort_rmr *)iort_node->node_data;
> > +	if (!rmr->rmr_offset || !rmr->rmr_count) {
> > +		pr_err(FW_BUG "Invalid RMR descriptor array, skipping RMR
> node %p\n",
> > +		       iort_node);
> > +		return -EINVAL;
> > +	}
> > +
> > +	rmr_desc = ACPI_ADD_PTR(struct acpi_iort_rmr_desc, iort_node,
> > +				rmr->rmr_offset);
> > +
> > +	ret = iort_rmr_desc_valid(rmr_desc, rmr->rmr_count);
> > +	if (ret) {
> > +		pr_err(FW_BUG "Invalid RMR descriptor[%d] for node %p,
> skipping...\n",
> > +		       i, iort_node);
> > +		return ret;
> > +	}
> > +
> > +	for (i = 0; i < rmr->rmr_count; i++, rmr_desc++) {
> > +		e = kmalloc(sizeof(*e), GFP_KERNEL);
> > +		if (!e)
> > +			return -ENOMEM;
> > +
> > +		e->sid = sid;
> > +		e->smmu = smmu;
> > +		e->rmr_desc = rmr_desc;
> > +		e->flags = rmr->flags;
> > +
> > +		list_add_tail(&e->list, &iort_rmr_list);
> > +	}
> > +
> > +	return 0;
> > +}
> >
> >   static void __init iort_init_platform_devices(void)
> >   {
> > @@ -1689,6 +1788,9 @@ static void __init iort_init_platform_devices(void)
> >
> >   		iort_enable_acs(iort_node);
> >
> > +		if (iort_table->revision == 3)
> > +			iort_parse_rmr(iort_node);
> > +
> >   		ops = iort_get_dev_cfg(iort_node);
> >   		if (ops) {
> >   			fwnode = acpi_alloc_fwnode_static();
> >