Re: [Xen-devel] [PATCH v5 05/22] xen/arm: ITS: Port ITS driver to Xen

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Vijay,

On 27/07/15 12:11, vijay.kilari@xxxxxxxxx wrote:
> From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
> 
> The linux driver is based on 4.1 with below commit id
> 
> 3ad2a5f57656a14d964b673a5a0e4ab0e583c870

This doesn't include commit 591e5bec13f15feb13fc445b6c9c59954711c4ac
"irqchip/gicv3-its: Fix mapping of LPIs to collections".

On the version 4 of this series, Ian [1] said that it would be very nice
to have a similar approach in Xen. I would like to see it too.

[..]

> diff --git a/xen/arch/arm/gic-v3-its.c b/xen/arch/arm/gic-v3-its.c
> new file mode 100644
> index 0000000..ba4110f
> --- /dev/null
> +++ b/xen/arch/arm/gic-v3-its.c

[..]

> +#define its_err(fmt, ...) its_print(XENLOG_ERR, fmt, ## __VA_ARGS__)
> +/* TODO: ratelimit for Xen messages */
> +#define its_err_ratelimited(fmt, ...)                                 \
> +    its_print(XENLOG_ERR, fmt, ## __VA_ARGS__)

The macro its_err_ratelimited is mostly used in function that are
accessible by the guest (via enable/disable LPI...). Which means that a
guest could theoretically hit the problem and DOS xen.

I would use XENLOG_G_ERR to have a rate limited until we fix it
correctly for XENLOG_ERR.

[..]

> +#ifdef DEBUG_GIC_ITS
> +void dump_cmd(its_cmd_block *cmd)

static void

and const its_cmd_block *cmd

> +{
> +    printk(XENLOG_DEBUG,
> +           "ITS: CMD[0] = 0x%lx CMD[1] = 0x%lx CMD[2] = 0x%lx CMD[3] = 
> 0x%lx\n",
> +           cmd->bits[0], cmd->bits[1], cmd->bits[2], cmd->bits[3]);
> +}
> +#else
> +void dump_cmd(its_cmd_block *cmd) { do {} while ( 0 ); }

ditto for static and const

Also, the do {} while 0 is not necessary given you are using function
and not macro.

> +#endif

> +void its_send_inv(struct its_device *dev, struct its_collection *col,
> +                  u32 event_id)

On a follow-up patch (see #15) you change the prototype to be static.
The static should be set now and not deferring until you use it just
because of compilation issue. This is a call to reorder the patches or
split them.

Also, if you include the commit I mentioned at the beginning of the
mail, you won't need to pass its_collection *col.

It would be more cleaner for the caller and defer the choice of the
collection within the function as Linux does.

[..]

> +void its_send_mapd(struct its_device *dev, int valid)

static void ...

> +{
> +    its_cmd_block cmd;
> +    unsigned long itt_addr;
> +    u8 size;
> +
> +    size = max(ilog2(dev->nr_lpis), 1);

Why do you need the max? dev->nr_lpis should always contains a valid value.

[..]

> +void its_send_mapvi(struct its_device *dev, struct its_collection *col,
> +                    u32 phys_id, u32 event)

All my remark on its_send_inv applies here too.

[..]

> +void its_send_discard(struct its_device *dev, struct its_collection *col,
> +                      u32 event)

All my remarks on its_send_inv applies here too.

[..]

> +unsigned long *its_lpi_alloc_chunks(int nirqs, int *base)

static unsigned long ...

[..]

> +void its_lpi_free(struct its_device *dev)

static void ...

[..]

> +static void its_cpu_init_lpis(void)
> +{
> +    void __iomem *rbase = gic_data_rdist().rbase;
> +    void *pend_page;
> +    u64 val, tmp;
> +
> +    /* If we didn't allocate the pending table yet, do it now */
> +    pend_page = gic_data_rdist().pend_page;
> +    if ( !pend_page )
> +    {
> +        paddr_t paddr;
> +        u32 order;

NIT: Newline here please.

> +        /*
> +         * The pending pages have to be at least 64kB aligned,
> +         * hence the 'max(LPI_PENDBASE_SZ, SZ_64K)' below.
> +         */

[..]

> +int __init its_init(struct rdist_prop *rdists)
> +{
> +    struct dt_device_node *np = NULL;
> +
> +    static const struct dt_device_match its_device_ids[] __initconst =
> +    {
> +        DT_MATCH_GIC_ITS,
> +        { /* sentinel */ },
> +    };
> +
> +    for (np = dt_find_matching_node(NULL, its_device_ids); np;
> +             np = dt_find_matching_node(np, its_device_ids))

The indentation looks wrong here.

> +        its_probe(np);
> +
> +    if ( list_empty(&its_nodes) )
> +    {
> +        its_warn("ITS: No ITS available, not enabling LPIs\n");
> +        return -ENXIO;
> +    }
> +
> +    gic_rdists = rdists;
> +    its_lpi_init(rdists->id_bits);
> +    its_alloc_lpi_tables();

I don't see much reason to change the order compare to Linux. Please
do

its_alloc_lpi_tables();
its_its_lpi_init(rdists->id_bits);

Regards,

[1] http://lists.xen.org/archives/html/xen-devel/2015-07/msg03369.html

-- 
Julien Grall

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