[PATCH v2] irqchip/gic-v3-its: Reset each ITS's BASERn register before probe

Marc Zyngier
2022-01-22T16:37:29Z

A recent bug report outlined that the way GICv4.1 is handled across
kexec is pretty bad. We can end-up in a situation where ITSs share
memory (this is the case when SVPET==1) and reprogram the base
registers, creating a situation where ITSs that are part of a given
affinity group see different pointers. Which is illegal. Boo.

In order to restore some sanity, reset the BASERn registers to 0
*before* probing any ITS. Although this isn't optimised at all,
this is only a once-per-boot cost, which shouldn't show up on
anyone's radar.

Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Jay Chen <jkchen@linux.alibaba.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211216190315.GA14220@lpieralisi
---

Notes:
* From v1: Fail probing if any ITS fails to reset.

drivers/irqchip/irq-gic-v3-its.c | 111 +++++++++++++++++++++++++------
1 file changed, 92 insertions(+), 19 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 7b8f1ec0ff78..8dd876445d99 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -4856,6 +4856,38 @@ static struct syscore_ops its_syscore_ops = {
.resume = its_restore_enable,
};

+static void __init __iomem *its_map_one(struct resource *res, int *err)
+{
+ void __iomem *its_base;
+ u32 val;
+
+ its_base = ioremap(res->start, SZ_64K);
+ if (!its_base) {
+ pr_warn("ITS@%pa: Unable to map ITS registers\n", &res->start);
+ *err = -ENOMEM;
+ return NULL;
+ }
+
+ val = readl_relaxed(its_base + GITS_PIDR2) & GIC_PIDR2_ARCH_MASK;
+ if (val != 0x30 && val != 0x40) {
+ pr_warn("ITS@%pa: No ITS detected, giving up\n", &res->start);
+ *err = -ENODEV;
+ goto out_unmap;
+ }
+
+ *err = its_force_quiescent(its_base);
+ if (*err) {
+ pr_warn("ITS@%pa: Failed to quiesce, giving up\n", &res->start);
+ goto out_unmap;
+ }
+
+ return its_base;
+
+out_unmap:
+ iounmap(its_base);
+ return NULL;
+}
+
static int its_init_domain(struct fwnode_handle *handle, struct its_node *its)
{
struct irq_domain *inner_domain;
@@ -4963,29 +4995,14 @@ static int __init its_probe_one(struct resource *res,
{
struct its_node *its;
void __iomem *its_base;
- u32 val, ctlr;
u64 baser, tmp, typer;
struct page *page;
+ u32 ctlr;
int err;

- its_base = ioremap(res->start, SZ_64K);
- if (!its_base) {
- pr_warn("ITS@%pa: Unable to map ITS registers\n", &res->start);
- return -ENOMEM;
- }
-
- val = readl_relaxed(its_base + GITS_PIDR2) & GIC_PIDR2_ARCH_MASK;
- if (val != 0x30 && val != 0x40) {
- pr_warn("ITS@%pa: No ITS detected, giving up\n", &res->start);
- err = -ENODEV;
- goto out_unmap;
- }
-
- err = its_force_quiescent(its_base);
- if (err) {
- pr_warn("ITS@%pa: Failed to quiesce, giving up\n", &res->start);
- goto out_unmap;
- }
+ its_base = its_map_one(res, &err);
+ if (!its_base)
+ return err;

pr_info("ITS %pR\n", res);

@@ -5249,6 +5266,23 @@ static int its_cpu_memreserve_lpi(unsigned int cpu)
return ret;
}

+/* Mark all the BASER registers as invalid before they get reprogrammed */
+static int __init its_reset_one(struct resource *res)
+{
+ void __iomem *its_base;
+ int err, i;
+
+ its_base = its_map_one(res, &err);
+ if (!its_base)
+ return err;
+
+ for (i = 0; i < GITS_BASER_NR_REGS; i++)
+ gits_write_baser(0, its_base + GITS_BASER + (i << 3));
+
+ iounmap(its_base);
+ return 0;
+}
+
static const struct of_device_id its_device_id[] = {
{ .compatible = "arm,gic-v3-its", },
{},
@@ -5259,6 +5293,26 @@ static int __init its_of_probe(struct device_node *node)
struct device_node *np;
struct resource res;

+ /*
+ * Make sure *all* the ITS are reset before we probe any, as
+ * they may be sharing memory. Don't bother warning on the
+ * first iteration, as any error will be caught on the second
+ * one.
+ */
+ for (np = of_find_matching_node(node, its_device_id); np;
+ np = of_find_matching_node(np, its_device_id)) {
+ int err;
+
+ if (!of_device_is_available(np) ||
+ !of_property_read_bool(np, "msi-controller") ||
+ of_address_to_resource(np, 0, &res))
+ continue;
+
+ err = its_reset_one(&res);
+ if (err)
+ return err;
+ }
+
for (np = of_find_matching_node(node, its_device_id); np;
np = of_find_matching_node(np, its_device_id)) {
if (!of_device_is_available(np))
@@ -5421,9 +5475,28 @@ static int __init gic_acpi_parse_madt_its(union acpi_subtable_headers *header,
return err;
}

+static int __init its_acpi_reset(union acpi_subtable_headers *header,
+ const unsigned long end)
+{
+ struct acpi_madt_generic_translator *its_entry;
+ struct resource res;
+
+ its_entry = (struct acpi_madt_generic_translator *)header;
+ res = (struct resource) {
+ .start = its_entry->base_address,
+ .end = its_entry->base_address + ACPI_GICV3_ITS_MEM_SIZE - 1,
+ .flags = IORESOURCE_MEM,
+ };
+
+ return its_reset_one(&res);
+}
+
static void __init its_acpi_probe(void)
{
acpi_table_parse_srat_its();
+ if (acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_TRANSLATOR,
+ its_acpi_reset, 0))
+ return;
acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_TRANSLATOR,
gic_acpi_parse_madt_its, 0);
acpi_its_srat_maps_free();
--
2.34.1