Re: 0b6bacc7874f - main - Add ofw_bus_iommu_map() that maps PCI requester ID to an IOMMU specifier based on "iommu-map" DTS property.

On Fri, May 06, 2022 at 09:25:40AM -0700, Ravi Pokala wrote:
> -----Original Message-----
> From: <owner-src-committers@freebsd.org> on behalf of Ruslan Bukin <br@FreeBSD.org>
> Date: 2022-05-06, Friday at 08:51
> To: <src-committers@FreeBSD.org>, <dev-commits-src-all@FreeBSD.org>, <dev-commits-src-main@FreeBSD.org>
> Subject: git: 0b6bacc7874f - main - Add ofw_bus_iommu_map() that maps PCI requester ID to an IOMMU specifier based on "iommu-map" DTS property.
> 
>     The branch main has been updated by br:
> 
>     URL: https://cgit.FreeBSD.org/src/commit/?id=0b6bacc7874f9c68ad35b06f1a7614171eb9ab10
> 
>     commit 0b6bacc7874f9c68ad35b06f1a7614171eb9ab10
>     Author:     Ruslan Bukin <br@FreeBSD.org>
>     AuthorDate: 2022-05-06 15:41:11 +0000
>     Commit:     Ruslan Bukin <br@FreeBSD.org>
>     CommitDate: 2022-05-06 15:48:04 +0000
> 
>         Add ofw_bus_iommu_map() that maps PCI requester ID to an IOMMU
>         specifier based on "iommu-map" DTS property.
> 
>         Sponsored by: UKRI
>     ---
>      sys/dev/ofw/ofw_bus_subr.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
>      sys/dev/ofw/ofw_bus_subr.h |  3 ++-
>      2 files changed, 46 insertions(+), 1 deletion(-)
> 
>     diff --git a/sys/dev/ofw/ofw_bus_subr.c b/sys/dev/ofw/ofw_bus_subr.c
>     index ea57d1086779..408d554b3c7f 100644
>     --- a/sys/dev/ofw/ofw_bus_subr.c
>     +++ b/sys/dev/ofw/ofw_bus_subr.c
>     @@ -491,6 +491,50 @@ ofw_bus_msimap(phandle_t node, uint16_t pci_rid, phandle_t *msi_parent,
>      	return (err);
>      }
> 
>     +int
>     +ofw_bus_iommu_map(phandle_t node, uint16_t pci_rid, phandle_t *iommu_parent,
>     +    uint32_t *iommu_rid)
>     +{
>     +	pcell_t mask, iommu_base, rid_base, rid_length;
>     +	uint32_t masked_rid;
>     +	pcell_t map[4];
>     +	ssize_t len;
>     +	int err, i;
>     +
>     +	len = OF_getproplen(node, "iommu-map");
>     +	if (len <= 0)
>     +		return (ENOENT);
>     +        if (len > sizeof(map))
>     +                return (ENOMEM);
>     +
>     +	len = OF_getencprop(node, "iommu-map", map, 16);
>     +
>     +	err = ENOENT;
>     +	mask = 0xffffffff;
>     +	OF_getencprop(node, "iommu-map-mask", &mask, sizeof(mask));
>     +
>     +	masked_rid = pci_rid & mask;
>     +	for (i = 0; i < len; i += 4) {
>     +		rid_base = map[i + 0];
>     +		rid_length = map[i + 3];
> 
> Hi Ruslan,
> 
> I'm confused by this. 'map' is declared as a 4-element array, which means 'map[i + 0]' and 'map[i + 3]' are both only valid when 'i' is 0. But 'i' is the loop iterator; doesn't that mean you're accessing outside the array after the 0th time through the loop?
> 
> Thanks,


Thanks, I'll fix this. I did not want to allocate memory here but it looks like we have to, since there is no limit on amount of entires in "iommu-map" property.

> 
> Ravi (rpokala@)
> 
>     +		if (masked_rid < rid_base ||
>     +		    masked_rid >= (rid_base + rid_length))
>     +			continue;
>     +
>     +		iommu_base = map[i + 2];
>     +
>     +		if (iommu_parent != NULL)
>     +			*iommu_parent = map[i + 1];
>     +		if (iommu_rid != NULL)
>     +			*iommu_rid = masked_rid - rid_base + iommu_base;
>     +		err = 0;
>     +		break;
>     +	}
>     +
>     +	return (err);
>     +}
>     +
>      static int
>      ofw_bus_reg_to_rl_helper(device_t dev, phandle_t node, pcell_t acells, pcell_t scells,
>          struct resource_list *rl, const char *reg_source)
>     diff --git a/sys/dev/ofw/ofw_bus_subr.h b/sys/dev/ofw/ofw_bus_subr.h
>     index 45709c92c1f7..89f291f92373 100644
>     --- a/sys/dev/ofw/ofw_bus_subr.h
>     +++ b/sys/dev/ofw/ofw_bus_subr.h
>     @@ -92,8 +92,9 @@ int	ofw_bus_lookup_imap(phandle_t, struct ofw_bus_iinfo *, void *, int,
>      int	ofw_bus_search_intrmap(void *, int, void *, int, void *, int, void *,
>      	    void *, void *, int, phandle_t *);
> 
>     -/* Routines for processing msi maps */
>     +/* Routines for processing msi and iommu maps. */
>      int ofw_bus_msimap(phandle_t, uint16_t, phandle_t *, uint32_t *);
>     +int ofw_bus_iommu_map(phandle_t, uint16_t, phandle_t *, uint32_t *);
> 
>      /* Routines for parsing device-tree data into resource lists. */
>      int ofw_bus_reg_to_rl(device_t, phandle_t, pcell_t, pcell_t,
> 
>