irqchip: gicv3-its: Allocate enough memory for the full range of DeviceID

The ITS table allocator is only allocating a single page per table.
This works fine for most things, but leads to silent lack of
interrupt delivery if we end-up with a device that has an ID that is
out of the range defined by a single page of memory. Even worse, depending
on the page size, behaviour changes, which is not a very good experience.

A solution is actually to allocate memory for the full range of ID that
the ITS supports. A massive waste memory wise, but at least a safe bet.

Tested on a Phytium SoC.

Tested-by: Chen Baozi <chenbaozi@kylinos.com.cn>
Acked-by: Chen Baozi <chenbaozi@kylinos.com.cn>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/1425659870-11832-3-git-send-email-marc.zyngier@arm.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

2 files changed, 23 insertions, 4 deletions

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index c217ebcf7a48..733b32fda390 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -806,14 +806,31 @@ static int its_alloc_tables(struct its_node *its)
                 u64 val = readq_relaxed(its->base + GITS_BASER + i * 8);
                 u64 type = GITS_BASER_TYPE(val);
                 u64 entry_size = GITS_BASER_ENTRY_SIZE(val);
+                int order = 0;
+                int alloc_size;
                 u64 tmp;
                 void *base;
 
                 if (type == GITS_BASER_TYPE_NONE)
                         continue;
 
-                /* We're lazy and only allocate a single page for now */
-                base = (void *)get_zeroed_page(GFP_KERNEL);
+                /*
+                 * Allocate as many entries as required to fit the
+                 * range of device IDs that the ITS can grok... The ID
+                 * space being incredibly sparse, this results in a
+                 * massive waste of memory.
+                 *
+                 * For other tables, only allocate a single page.
+                 */
+                if (type == GITS_BASER_TYPE_DEVICE) {
+                        u64 typer = readq_relaxed(its->base + GITS_TYPER);
+                        u32 ids = GITS_TYPER_DEVBITS(typer);
+
+                        order = get_order((1UL << ids) * entry_size);
+                }
+
+                alloc_size = (1 << order) * PAGE_SIZE;
+                base = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
                 if (!base) {
                         err = -ENOMEM;
                         goto out_free;
@@ -841,7 +858,7 @@ retry_baser:
                         break;
                 }
 
-                val |= (PAGE_SIZE / psz) - 1;
+                val |= (alloc_size / psz) - 1;
 
                 writeq_relaxed(val, its->base + GITS_BASER + i * 8);
                 tmp = readq_relaxed(its->base + GITS_BASER + i * 8);
@@ -882,7 +899,7 @@ retry_baser:
                 }
 
                 pr_info("ITS: allocated %d %s @%lx (psz %dK, shr %d)\n",
-                        (int)(PAGE_SIZE / entry_size),
+                        (int)(alloc_size / entry_size),
                         its_base_type_string[type],
                         (unsigned long)virt_to_phys(base),
                         psz / SZ_1K, (int)shr >> GITS_BASER_SHAREABILITY_SHIFT);
diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
index 800544bc7bfd..cbdd440d486d 100644
--- a/include/linux/irqchip/arm-gic-v3.h
+++ b/include/linux/irqchip/arm-gic-v3.h
@@ -166,6 +166,8 @@
 
 #define GITS_TRANSLATER                 0x10040
 
+#define GITS_TYPER_DEVBITS_SHIFT        13
+#define GITS_TYPER_DEVBITS(r)           ((((r) >> GITS_TYPER_DEVBITS_SHIFT) & 0x1f) + 1)
 #define GITS_TYPER_PTA                  (1UL << 19)
 
 #define GITS_CBASER_VALID               (1UL << 63)