Patch "arm64: run softirqs on the per-CPU IRQ stack" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    arm64: run softirqs on the per-CPU IRQ stack

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-run-softirqs-on-the-per-cpu-irq-stack.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit d142e3103d8d9191fba4e1ffd56b2cb0f731f87d
Author: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Date:   Mon Aug 15 20:47:39 2022 +0800

    arm64: run softirqs on the per-CPU IRQ stack
    
    [ Upstream commit 8eb858c44b98e0326bb32fca34ae671995cd73bb ]
    
    Currently arm64 supports per-CPU IRQ stack, but softirqs
    are still handled in the task context.
    
    Since any call to local_bh_enable() at any level in the task's
    call stack may trigger a softirq processing run, which could
    potentially cause a task stack overflow if the combined stack
    footprints exceed the stack's size, let's run these softirqs
    on the IRQ stack as well.
    
    Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
    Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx>
    Acked-by: Will Deacon <will@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20220815124739.15948-1-zhengqi.arch@xxxxxxxxxxxxx
    Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1e5a03d51d46..73f411975357 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -221,6 +221,7 @@ config ARM64
 	select HAVE_ARCH_USERFAULTFD_MINOR if USERFAULTFD
 	select TRACE_IRQFLAGS_SUPPORT
 	select TRACE_IRQFLAGS_NMI_SUPPORT
+	select HAVE_SOFTIRQ_ON_OWN_STACK
 	help
 	  ARM 64-bit (AArch64) Linux support.
 
diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
index bda49430c9ea..38dbd3828f13 100644
--- a/arch/arm64/kernel/irq.c
+++ b/arch/arm64/kernel/irq.c
@@ -21,7 +21,9 @@
 #include <linux/seq_file.h>
 #include <linux/vmalloc.h>
 #include <asm/daifflags.h>
+#include <asm/exception.h>
 #include <asm/vmap_stack.h>
+#include <asm/softirq_stack.h>
 
 /* Only access this in an NMI enter/exit */
 DEFINE_PER_CPU(struct nmi_ctx, nmi_contexts);
@@ -71,6 +73,18 @@ static void init_irq_stacks(void)
 }
 #endif
 
+#ifndef CONFIG_PREEMPT_RT
+static void ____do_softirq(struct pt_regs *regs)
+{
+	__do_softirq();
+}
+
+void do_softirq_own_stack(void)
+{
+	call_on_irq_stack(NULL, ____do_softirq);
+}
+#endif
+
 static void default_handle_irq(struct pt_regs *regs)
 {
 	panic("IRQ taken without a root IRQ handler\n");