| Message ID | 20180306155132.8757-1-ard.biesheuvel@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 06/03/18 15:51, Ard Biesheuvel wrote: > 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> > --- > drivers/irqchip/irq-gic-v3-its.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c > index 1d3056f53747..ee488c468400 100644 > --- a/drivers/irqchip/irq-gic-v3-its.c > +++ b/drivers/irqchip/irq-gic-v3-its.c > @@ -1412,7 +1412,7 @@ 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) > #define ITS_MAX_LPI_NRBITS 16 /* 64K LPIs */ > > static unsigned long *lpi_bitmap; > @@ -2123,7 +2123,7 @@ static struct its_device *its_create_device(struct its_node *its, u32 dev_id, > * of two entries. No, the architecture doesn't let you > * express an ITT with a single entry. This comment feels slightly out of place now. > */ > - 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); > Otherwise, this looks good to me. I'll amend the comment when applying the patch, no need to respin. Thanks, M.
On 6 March 2018 at 16:00, Marc Zyngier <marc.zyngier@arm.com> wrote: > On 06/03/18 15:51, Ard Biesheuvel wrote: >> 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> >> --- >> drivers/irqchip/irq-gic-v3-its.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c >> index 1d3056f53747..ee488c468400 100644 >> --- a/drivers/irqchip/irq-gic-v3-its.c >> +++ b/drivers/irqchip/irq-gic-v3-its.c >> @@ -1412,7 +1412,7 @@ 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) >> #define ITS_MAX_LPI_NRBITS 16 /* 64K LPIs */ >> >> static unsigned long *lpi_bitmap; >> @@ -2123,7 +2123,7 @@ static struct its_device *its_create_device(struct its_node *its, u32 dev_id, >> * of two entries. No, the architecture doesn't let you >> * express an ITT with a single entry. > > This comment feels slightly out of place now. > Indeed. >> */ >> - 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); >> > > Otherwise, this looks good to me. I'll amend the comment when applying > the patch, no need to respin. > Excellent, thanks!
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c index 1d3056f53747..ee488c468400 100644 --- a/drivers/irqchip/irq-gic-v3-its.c +++ b/drivers/irqchip/irq-gic-v3-its.c @@ -1412,7 +1412,7 @@ 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) #define ITS_MAX_LPI_NRBITS 16 /* 64K LPIs */ static unsigned long *lpi_bitmap; @@ -2123,7 +2123,7 @@ static struct its_device *its_create_device(struct its_node *its, u32 dev_id, * of two entries. No, the architecture doesn't let you * express an ITT with a single entry. */ - 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);
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> --- drivers/irqchip/irq-gic-v3-its.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)