4.4-stable review patch. If anyone has any objections, please let me know.
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From: Ard Biesheuvel ard.biesheuvel@linaro.org
commit 4f2c7583e33eb08dc09dd2e25574b80175ba7d93 upstream.
When struct its_device instances are created, the nr_ites member will be set to a power of 2 that equals or exceeds the requested number of MSIs passed to the msi_prepare() callback. At the same time, the LPI map is allocated to be some multiple of 32 in size, where the allocated size may be less than the requested size depending on whether a contiguous range of sufficient size is available in the global LPI bitmap.
This may result in the situation where the nr_ites < nr_lpis, and since nr_ites is what we program into the hardware when we map the device, the additional LPIs will be non-functional.
For bog standard hardware, this does not really matter. However, in cases where ITS device IDs are shared between different PCIe devices, we may end up allocating these additional LPIs without taking into account that they don't actually work.
So let's make nr_ites at least 32. This ensures that all allocated LPIs are 'live', and that its_alloc_device_irq() will fail when attempts are made to allocate MSIs beyond what was allocated in the first place.
Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org [maz: updated comment] Signed-off-by: Marc Zyngier marc.zyngier@arm.com [ardb: trivial tweak of unrelated context] Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/irqchip/irq-gic-v3-its.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
--- a/drivers/irqchip/irq-gic-v3-its.c +++ b/drivers/irqchip/irq-gic-v3-its.c @@ -663,7 +663,7 @@ static struct irq_chip its_irq_chip = { * This gives us (((1UL << id_bits) - 8192) >> 5) possible allocations. */ #define IRQS_PER_CHUNK_SHIFT 5 -#define IRQS_PER_CHUNK (1 << IRQS_PER_CHUNK_SHIFT) +#define IRQS_PER_CHUNK (1UL << IRQS_PER_CHUNK_SHIFT)
static unsigned long *lpi_bitmap; static u32 lpi_chunks; @@ -1168,11 +1168,10 @@ static struct its_device *its_create_dev
dev = kzalloc(sizeof(*dev), GFP_KERNEL); /* - * At least one bit of EventID is being used, hence a minimum - * of two entries. No, the architecture doesn't let you - * express an ITT with a single entry. + * We allocate at least one chunk worth of LPIs bet device, + * and thus that many ITEs. The device may require less though. */ - nr_ites = max(2UL, roundup_pow_of_two(nvecs)); + nr_ites = max(IRQS_PER_CHUNK, roundup_pow_of_two(nvecs)); sz = nr_ites * its->ite_size; sz = max(sz, ITS_ITT_ALIGN) + ITS_ITT_ALIGN - 1; itt = kzalloc(sz, GFP_KERNEL);