Re: [PATCH] irqchipi/gic-v4: Ensure accessing the correct RD when and writing INVLPIR
From: Marc Zyngier
Date: Wed Apr 12 2023 - 05:42:59 EST
On Wed, 12 Apr 2023 05:15:10 +0100,
Kunkun Jiang <jiangkunkun@xxxxxxxxxx> wrote:
>
> commit f3a059219bc7 ("irqchip/gic-v4.1: Ensure mutual exclusion between
> vPE affinity change and RD access") tried to address the race
> between the RD accesses and the vPE affinity change, but somehow
> forgot to take GICR_INVLPIR into account. Let's take the vpe_lock
> before evaluating vpe->col_idx to fix it.
>
> Fixes: f3a059219bc7 ("irqchip/gic-v4.1: Ensure mutual exclusion between vPE affinity change and RD access")
> Signed-off-by: Kunkun Jiang <jiangkunkun@xxxxxxxxxx>
> Signed-off-by: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
> Signed-off-by: Nianyao Tang <tangnianyao@xxxxxxxxxx>
Yup, nice catch. A few remarks though:
- the subject looks odd: there is a spurious 'and' there, and it
doesn't say this is all about VPE doorbell invalidation (the code
that deals with direct LPI is otherwise fine)
- the SoB chain is also odd. You should be last in the chain, and all
the others have Co-developed-by tags in addition to the SoB, unless
you wanted another tag
- I'm curious about how you triggered the issue. Could you please
elaborate on that>
Finally, I think we can fix it in a better way, see below:
> ---
> drivers/irqchip/irq-gic-v3-its.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 586271b8aa39..041f06922587 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -3943,13 +3943,17 @@ static void its_vpe_send_inv(struct irq_data *d)
>
> if (gic_rdists->has_direct_lpi) {
> void __iomem *rdbase;
> + unsigned long flags;
> + int cpu;
>
> /* Target the redistributor this VPE is currently known on */
> - raw_spin_lock(&gic_data_rdist_cpu(vpe->col_idx)->rd_lock);
> - rdbase = per_cpu_ptr(gic_rdists->rdist, vpe->col_idx)->rd_base;
> + cpu = vpe_to_cpuid_lock(vpe, &flags);
> + raw_spin_lock(&gic_data_rdist_cpu(cpu)->rd_lock);
> + rdbase = per_cpu_ptr(gic_rdists->rdist, cpu)->rd_base;
> gic_write_lpir(d->parent_data->hwirq, rdbase + GICR_INVLPIR);
> wait_for_syncr(rdbase);
> - raw_spin_unlock(&gic_data_rdist_cpu(vpe->col_idx)->rd_lock);
> + raw_spin_unlock(&gic_data_rdist_cpu(cpu)->rd_lock);
> + vpe_to_cpuid_unlock(vpe, flags);
> } else {
> its_vpe_send_cmd(vpe, its_send_inv);
> }
The main reason this bug crept in is that we have a some pretty silly
code duplication going on.
Wouldn't it be nice if irq_to_cpuid() could work out whether it is
dealing with a LPI or a VLPI like it does today, but also directly
with a VPE? We could then use the same code as derect_lpi_inv(). I
came up with this the hack below, which is totally untested as I don't
have access to GICv4.1 HW.
Could you give it a spin?
Thanks,
M.
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 586271b8aa39..cfb8be3e17d6 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -271,13 +271,24 @@ static void vpe_to_cpuid_unlock(struct its_vpe *vpe, unsigned long flags)
raw_spin_unlock_irqrestore(&vpe->vpe_lock, flags);
}
+static struct irq_chip its_vpe_irq_chip;
+
static int irq_to_cpuid_lock(struct irq_data *d, unsigned long *flags)
{
- struct its_vlpi_map *map = get_vlpi_map(d);
+ struct its_vpe *vpe = NULL;
int cpu;
- if (map) {
- cpu = vpe_to_cpuid_lock(map->vpe, flags);
+ if (d->chip == &its_vpe_irq_chip)
+ vpe = irq_data_get_irq_chip_data(d);
+
+ if (!vpe) {
+ struct its_vlpi_map *map = get_vlpi_map(d);
+ if (map)
+ vpe = map->vpe;
+ }
+
+ if (vpe) {
+ cpu = vpe_to_cpuid_lock(vpe, flags);
} else {
/* Physical LPIs are already locked via the irq_desc lock */
struct its_device *its_dev = irq_data_get_irq_chip_data(d);
@@ -291,9 +302,18 @@ static int irq_to_cpuid_lock(struct irq_data *d, unsigned long *flags)
static void irq_to_cpuid_unlock(struct irq_data *d, unsigned long flags)
{
- struct its_vlpi_map *map = get_vlpi_map(d);
+ struct its_vpe *vpe = NULL;
+
+ if (d->chip == &its_vpe_irq_chip)
+ vpe = irq_data_get_irq_chip_data(d);
+
+ if (vpe) {
+ struct its_vlpi_map *map = get_vlpi_map(d);
+ if (map)
+ vpe = map->vpe;
+ }
- if (map)
+ if (vpe)
vpe_to_cpuid_unlock(map->vpe, flags);
}
@@ -1431,14 +1451,29 @@ static void wait_for_syncr(void __iomem *rdbase)
cpu_relax();
}
-static void direct_lpi_inv(struct irq_data *d)
+static void __direct_lpi_inv(struct irq_data *d, u64 val)
{
- struct its_vlpi_map *map = get_vlpi_map(d);
void __iomem *rdbase;
unsigned long flags;
- u64 val;
int cpu;
+ /* Target the redistributor this LPI is currently routed to */
+ cpu = irq_to_cpuid_lock(d, &flags);
+ raw_spin_lock(&gic_data_rdist_cpu(cpu)->rd_lock);
+
+ rdbase = per_cpu_ptr(gic_rdists->rdist, cpu)->rd_base;
+ gic_write_lpir(val, rdbase + GICR_INVLPIR);
+ wait_for_syncr(rdbase);
+
+ raw_spin_unlock(&gic_data_rdist_cpu(cpu)->rd_lock);
+ irq_to_cpuid_unlock(d, flags);
+}
+
+static void direct_lpi_inv(struct irq_data *d)
+{
+ struct its_vlpi_map *map = get_vlpi_map(d);
+ u64 val;
+
if (map) {
struct its_device *its_dev = irq_data_get_irq_chip_data(d);
@@ -1451,15 +1486,7 @@ static void direct_lpi_inv(struct irq_data *d)
val = d->hwirq;
}
- /* Target the redistributor this LPI is currently routed to */
- cpu = irq_to_cpuid_lock(d, &flags);
- raw_spin_lock(&gic_data_rdist_cpu(cpu)->rd_lock);
- rdbase = per_cpu_ptr(gic_rdists->rdist, cpu)->rd_base;
- gic_write_lpir(val, rdbase + GICR_INVLPIR);
-
- wait_for_syncr(rdbase);
- raw_spin_unlock(&gic_data_rdist_cpu(cpu)->rd_lock);
- irq_to_cpuid_unlock(d, flags);
+ __direct_lpi_inv(d, val);
}
static void lpi_update_config(struct irq_data *d, u8 clr, u8 set)
@@ -3941,18 +3968,10 @@ static void its_vpe_send_inv(struct irq_data *d)
{
struct its_vpe *vpe = irq_data_get_irq_chip_data(d);
- if (gic_rdists->has_direct_lpi) {
- void __iomem *rdbase;
-
- /* Target the redistributor this VPE is currently known on */
- raw_spin_lock(&gic_data_rdist_cpu(vpe->col_idx)->rd_lock);
- rdbase = per_cpu_ptr(gic_rdists->rdist, vpe->col_idx)->rd_base;
- gic_write_lpir(d->parent_data->hwirq, rdbase + GICR_INVLPIR);
- wait_for_syncr(rdbase);
- raw_spin_unlock(&gic_data_rdist_cpu(vpe->col_idx)->rd_lock);
- } else {
+ if (gic_rdists->has_direct_lpi)
+ __direct_lpi_inv(d, d->parent_data->hwirq);
+ else
its_vpe_send_cmd(vpe, its_send_inv);
- }
}
static void its_vpe_mask_irq(struct irq_data *d)
--
Without deviation from the norm, progress is not possible.