6.12-stable review patch. If anyone has any objections, please let me know.
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From: Christian Bruel christian.bruel@foss.st.com
[ Upstream commit 2ef3886ce626dcdab0cbc452dbbebc19f57133d8 ]
The PCI Local Bus Specification 3.0 (section 6.8.1.6) allows modifying the low-order bits of the MSI Message DATA register to encode nr_irqs interrupt numbers in the log2(nr_irqs) bits for the domain.
The problem arises if the base vector (GICV2m base spi) is not aligned with nr_irqs; in this case, the low-order log2(nr_irqs) bits from the base vector conflict with the nr_irqs masking, causing the wrong MSI interrupt to be identified.
To fix this, use bitmap_find_next_zero_area_off() instead of bitmap_find_free_region() to align the initial base vector with nr_irqs.
Signed-off-by: Christian Bruel christian.bruel@foss.st.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/all/20250902091045.220847-1-christian.bruel@foss.st.... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/irqchip/irq-gic-v2m.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/drivers/irqchip/irq-gic-v2m.c b/drivers/irqchip/irq-gic-v2m.c index a1e370d0200f1..b5479c552b776 100644 --- a/drivers/irqchip/irq-gic-v2m.c +++ b/drivers/irqchip/irq-gic-v2m.c @@ -156,14 +156,19 @@ static int gicv2m_irq_domain_alloc(struct irq_domain *domain, unsigned int virq, { msi_alloc_info_t *info = args; struct v2m_data *v2m = NULL, *tmp; - int hwirq, offset, i, err = 0; + int hwirq, i, err = 0; + unsigned long offset; + unsigned long align_mask = nr_irqs - 1;
spin_lock(&v2m_lock); list_for_each_entry(tmp, &v2m_nodes, entry) { - offset = bitmap_find_free_region(tmp->bm, tmp->nr_spis, - get_count_order(nr_irqs)); - if (offset >= 0) { + unsigned long align_off = tmp->spi_start - (tmp->spi_start & ~align_mask); + + offset = bitmap_find_next_zero_area_off(tmp->bm, tmp->nr_spis, 0, + nr_irqs, align_mask, align_off); + if (offset < tmp->nr_spis) { v2m = tmp; + bitmap_set(v2m->bm, offset, nr_irqs); break; } }