Re: [PATCH] arm64/irq: report bug if NR_IPI greater than max SGI during compile time

From: Marc Zyngier
Date: Tue Dec 08 2020 - 04:32:49 EST


On 2020-12-08 09:21, Pingfan Liu wrote:
Although there is a runtime WARN_ON() when NR_IPR > max SGI, it had better
do the check during built time, and associate these related code together.

Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Jason Cooper <jason@xxxxxxxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
To: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
arch/arm64/kernel/smp.c | 2 ++
drivers/irqchip/irq-gic-v3.c | 2 +-
drivers/irqchip/irq-gic.c | 2 +-
include/linux/irqchip/arm-gic-common.h | 2 ++
4 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 18e9727..9fc383c 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -33,6 +33,7 @@
#include <linux/kernel_stat.h>
#include <linux/kexec.h>
#include <linux/kvm_host.h>
+#include <linux/irqchip/arm-gic-common.h>

#include <asm/alternative.h>
#include <asm/atomic.h>
@@ -76,6 +77,7 @@ enum ipi_msg_type {
IPI_WAKEUP,
NR_IPI
};
+static_assert(NR_IPI <= MAX_SGI_NUM);

I am trying *very hard* to remove dependencies between the architecture
code and random drivers, so this kind of check really is counter-productive.

Driver code should not have to know the number of IPIs, because there is
no requirement that all IPIs should map 1:1 to SGIs. Conflating the two
is already wrong, and I really don't want to add more of that.

Thanks,

M.
--
Jazz is not dead. It just smells funny...