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

-----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,

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,