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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Thu, 7 Jul 2022 16:41:08 +0200
Message-ID: <CAK8P3a17A1t=qkyToQNVnuVfGPp-7VpFx5qJ-gmpyrkJ3yRXTw@mail.gmail.com>
Subject: Re: [RFC PATCH 2/2] arm64: support HAVE_IRQ_EXIT_ON_IRQ_STACK
To:     Qi Zheng <zhengqi.arch@bytedance.com>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Thu, Jul 7, 2022 at 3:38 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
> On 2022/7/7 20:49, Arnd Bergmann wrote:
> > On Thu, Jul 7, 2022 at 1:05 PM Qi Zheng <zhengqi.arch@bytedance.com> wrote:
>           * Restore the SP from the FP, and restore the FP and LR from
> the frame
>           * record.
>           */
> -       mov     sp, x29
> +999:   mov     sp, x29
>          ldp     x29, x30, [sp], #16
>   #ifdef CONFIG_SHADOW_CALL_STACK
>          ldp     scs_sp, xzr, [sp], #16
>
> But this also requires a new parameter in do_interrupt_handler.
>
> I also considered implementing call_on_irq_stack() for nmi and irq
> separately, but later think it's unnecessary.

What I had in mind was something along the lines of

diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 56cefd33eb8e..432042b91588 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -270,10 +270,7 @@ static void do_interrupt_handler(struct pt_regs *regs,
 {
        struct pt_regs *old_regs = set_irq_regs(regs);

-       if (on_thread_stack())
-               call_on_irq_stack(regs, handler);
-       else
-               handler(regs);
+       handler(regs);

        set_irq_regs(old_regs);
 }
@@ -473,16 +470,31 @@ static void noinstr el1_interrupt(struct pt_regs *regs,
                __el1_irq(regs, handler);
 }

-asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs)
+static void noinstr el1_irq(struct pt_regs *regs)
 {
        el1_interrupt(regs, handle_arch_irq);
 }

-asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs)
+asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs)
+{
+       if (on_thread_stack())
+               call_on_irq_stack(regs, el1_irq);
+       else
+               el1_irq(regs);
+}
+
+static void noinstr el1_fiq(struct pt_regs *regs)
 {
        el1_interrupt(regs, handle_arch_fiq);
 }

+asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs)
+{
+        if (on_thread_stack())
+               call_on_irq_stack(regs, el1_fiq);
+       else
+               el1_fiq(regs);
+}
+
 asmlinkage void noinstr el1h_64_error_handler(struct pt_regs *regs)
 {
        unsigned long esr = read_sysreg(esr_el1);
@@ -713,7 +731,7 @@ static void noinstr
__el0_irq_handler_common(struct pt_regs *regs)

 asmlinkage void noinstr el0t_64_irq_handler(struct pt_regs *regs)
 {
-       __el0_irq_handler_common(regs);
+       call_on_irq_stack(regs, __el0_irq_handler_common);
 }

 static void noinstr __el0_fiq_handler_common(struct pt_regs *regs)
@@ -723,7 +741,7 @@ static void noinstr
__el0_fiq_handler_common(struct pt_regs *regs)

 asmlinkage void noinstr el0t_64_fiq_handler(struct pt_regs *regs)
 {
-       __el0_fiq_handler_common(regs);
+       call_on_irq_stack(regs, __el0_fiq_handler_common);
 }

 static void noinstr __el0_error_handler_common(struct pt_regs *regs)
@@ -807,12 +825,12 @@ asmlinkage void noinstr
el0t_32_sync_handler(struct pt_regs *regs)

 asmlinkage void noinstr el0t_32_irq_handler(struct pt_regs *regs)
 {
-       __el0_irq_handler_common(regs);
+       call_on_irq_stack(regs, __el0_irq_handler_common);
 }

 asmlinkage void noinstr el0t_32_fiq_handler(struct pt_regs *regs)
 {
-       __el0_fiq_handler_common(regs);
+       call_on_irq_stack(regs, __el0_fiq_handler_common);
 }

 asmlinkage void noinstr el0t_32_error_handler(struct pt_regs *regs)

Not sure if that works.

        Arnd