Hi Doug,
On Thu, Jun 01, 2023 at 02:31:45PM -0700, Douglas Anderson wrote:
> From: Sumit Garg <sumit.g...@linaro.org>
>
> Add support to handle SGIs as pseudo NMIs. As SGIs or IPIs default to a
> special flow handler: handle_percpu_devid_fasteoi_ipi(), so skip NMI
> handler update in case of SGIs.
I couldn't find handle_percpu_devid_fasteoi_ipi() in mainline, and when
researching I found that we changed that in commit:
6abbd6988971aaa6 ("irqchip/gic, gic-v3: Make SGIs use
handle_percpu_devid_irq()")
... which was in v5.11, so it looks like this is stale?
Since that commit, SGIs are treated the same as PPIs/EPPIs, and use
handle_percpu_devid_irq() by default.
IIUC handle_percpu_devid_irq() isn't NMI safe, and so to run in an NMI context
those should use handle_percpu_devid_fasteoi_nmi().
Marc, does that sound right to you? i.e. SGI NMIs should be handled exactly the
same as PPI NMIs, and use handle_percpu_devid_fasteoi_nmi()?
I have some comments below assuming that SGI NMIs should use
handle_percpu_devid_fasteoi_nmi().
> Also, enable NMI support prior to gic_smp_init() as allocation of SGIs
> as IRQs/NMIs happen as part of this routine.
This bit looks fine to me.
> Signed-off-by: Sumit Garg <sumit.g...@linaro.org>
> Reviewed-by: Masayoshi Mizuma <m.miz...@jp.fujitsu.com>
> Tested-by: Chen-Yu Tsai <w...@csie.org>
> Signed-off-by: Douglas Anderson <diand...@chromium.org>
> ---
>
> (no changes since v1)
>
> drivers/irqchip/irq-gic-v3.c | 29 +++++++++++++++++++++--------
> 1 file changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 0c6c1af9a5b7..ed37e02d4c5f 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -525,6 +525,7 @@ static u32 gic_get_ppi_index(struct irq_data *d)
> static int gic_irq_nmi_setup(struct irq_data *d)
> {
> struct irq_desc *desc = irq_to_desc(d->irq);
> + u32 idx;
>
> if (!gic_supports_nmi())
> return -EINVAL;
> @@ -542,16 +543,22 @@ static int gic_irq_nmi_setup(struct irq_data *d)
> return -EINVAL;
>
> /* desc lock should already be held */
> - if (gic_irq_in_rdist(d)) {
> - u32 idx = gic_get_ppi_index(d);
> + switch (get_intid_range(d)) {
> + case SGI_RANGE:
> + break;
> + case PPI_RANGE:
> + case EPPI_RANGE:
> + idx = gic_get_ppi_index(d);
>
> /* Setting up PPI as NMI, only switch handler for first NMI */
> if (!refcount_inc_not_zero(&ppi_nmi_refs[idx])) {
> refcount_set(&ppi_nmi_refs[idx], 1);
> desc->handle_irq = handle_percpu_devid_fasteoi_nmi;
> }
> - } else {
> + break;
> + default:
> desc->handle_irq = handle_fasteoi_nmi;
> + break;
> }
As above, I reckon this isn't right, and we should treat all rdist interrupts
(which are all percpu) the same.
I reckon what we should be doing here is make ppi_nmi_refs cover all of the
rdist interrupts (e.g. make that rdist_nmi_refs, add a gic_get_rdist_idx()
helper), and then here have something like:
if (gic_irq_in_rdist(d)) {
u32 idx = gic_get_rdist_idx(d);
/*
* Setting up a percpu interrupt as NMI, only switch handler
* for first NMI
*/
if (!refcount_inc_not_zero(&rdist_nmi_refs[idx])) {
refcount_set(&ppi_nmi_refs[idx], 1);
desc->handle_irq = handle_percpu_devid_fasteoi_nmi;
}
}
... as an aside, it'd be nicer if we could switch the handler at request time,
as then we wouldn't need the refcount at all, but I couldn't see a good irqchip
hook to hang that off, so I don't think that needs to change as a prerequisite.
>
> gic_irq_set_prio(d, GICD_INT_NMI_PRI);
> @@ -562,6 +569,7 @@ static int gic_irq_nmi_setup(struct irq_data *d)
> static void gic_irq_nmi_teardown(struct irq_data *d)
> {
> struct irq_desc *desc = irq_to_desc(d->irq);
> + u32 idx;
>
> if (WARN_ON(!gic_supports_nmi()))
> return;
> @@ -579,14 +587,20 @@ static void gic_irq_nmi_teardown(struct irq_data *d)
> return;
>
> /* desc lock should already be held */
> - if (gic_irq_in_rdist(d)) {
> - u32 idx = gic_get_ppi_index(d);
> + switch (get_intid_range(d)) {
> + case SGI_RANGE:
> + break;
> + case PPI_RANGE:
> + case EPPI_RANGE:
> + idx = gic_get_ppi_index(d);
>
> /* Tearing down NMI, only switch handler for last NMI */
> if (refcount_dec_and_test(&ppi_nmi_refs[idx]))
> desc->handle_irq = handle_percpu_devid_irq;
> - } else {
> + break;
> + default:
> desc->handle_irq = handle_fasteoi_irq;
> + break;
> }
Same comments as for gic_irq_nmi_setup() here.
>
> gic_irq_set_prio(d, GICD_INT_DEF_PRI);
> @@ -2001,6 +2015,7 @@ static int __init gic_init_bases(phys_addr_t
> dist_phys_base,
>
> gic_dist_init();
> gic_cpu_init();
> + gic_enable_nmi_support();
> gic_smp_init();
> gic_cpu_pm_init();
>
> @@ -2013,8 +2028,6 @@ static int __init gic_init_bases(phys_addr_t
> dist_phys_base,
> gicv2m_init(handle, gic_data.domain);
> }
>
> - gic_enable_nmi_support();
> -
This bit looks fine to me.
Thanks,
Mark.
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