On Tue, May 20, 2025 at 10:19:47AM +0200, Clément Léger wrote:
>
>
> On 20/05/2025 01:32, Charlie Jenkins wrote:
> > On Thu, May 15, 2025 at 10:22:10AM +0200, Clément Léger wrote:
> >> Split the code that check for the uniformity of misaligned accesses
> >> performance on all cpus from check_unaligned_access_emulated_all_cpus()
> >> to its own function which will be used for delegation check. No
> >> functional changes intended.
> >>
> >> Signed-off-by: Clément Léger <cle...@rivosinc.com>
> >> Reviewed-by: Andrew Jones <ajo...@ventanamicro.com>
> >> ---
> >> arch/riscv/kernel/traps_misaligned.c | 20 ++++++++++++++------
> >> 1 file changed, 14 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/arch/riscv/kernel/traps_misaligned.c
> >> b/arch/riscv/kernel/traps_misaligned.c
> >> index e551ba17f557..287ec37021c8 100644
> >> --- a/arch/riscv/kernel/traps_misaligned.c
> >> +++ b/arch/riscv/kernel/traps_misaligned.c
> >> @@ -647,6 +647,18 @@ bool __init
> >> check_vector_unaligned_access_emulated_all_cpus(void)
> >> }
> >> #endif
> >>
> >> +static bool all_cpus_unaligned_scalar_access_emulated(void)
> >> +{
> >> + int cpu;
> >> +
> >> + for_each_online_cpu(cpu)
> >> + if (per_cpu(misaligned_access_speed, cpu) !=
> >
> > misaligned_access_speed is only defined when
> > CONFIG_RISCV_SCALAR_MISALIGNED. This function should return false when
> > !CONFIG_RISCV_SCALAR_MISALIGNED and only use this logic otherwise.
>
> Hi Charlie,
>
> misaligned_access_speed is defined in unaligned_access_speed.c which is
> compiled based on CONFIG_RISCV_MISALIGNED (ditto for trap_misaligned.c)
>
> obj-$(CONFIG_RISCV_MISALIGNED) += unaligned_access_speed.o
>
> However, the declaration for it in the header cpu-feature.h however is
> under a CONFIG_RISCV_SCALAR_MISALIGNED ifdef. So either the declaration
> or the definition is wrong but the ifdefery soup makes it quite
> difficult to understand what's going on.
>
> I would suggest to move the DECLARE_PER_CPU under
> CONFIG_RISCV_MISALIGNED so that it reduces ifdef in traps_misaligned as
> well.
Here is the patch I am using locally for testing purposes, but if there
is a way to reduce the number of ifdefs that is probably the better way to go:
>From 18f9a056d3b597934c931abdf72fb6e775ccb714 Mon Sep 17 00:00:00 2001
From: Charlie Jenkins <char...@rivosinc.com>
Date: Mon, 19 May 2025 16:35:51 -0700
Subject: [PATCH] fixup! riscv: misaligned: move emulated access uniformity
check in a function
---
arch/riscv/kernel/traps_misaligned.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/arch/riscv/kernel/traps_misaligned.c
b/arch/riscv/kernel/traps_misaligned.c
index f3ab84bc4632..1449c6a4ac21 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -647,6 +647,10 @@ bool __init
check_vector_unaligned_access_emulated_all_cpus(void)
}
#endif
+#ifdef CONFIG_RISCV_SCALAR_MISALIGNED
+
+static bool unaligned_ctl __read_mostly;
+
static bool all_cpus_unaligned_scalar_access_emulated(void)
{
int cpu;
@@ -659,10 +663,6 @@ static bool all_cpus_unaligned_scalar_access_emulated(void)
return true;
}
-#ifdef CONFIG_RISCV_SCALAR_MISALIGNED
-
-static bool unaligned_ctl __read_mostly;
-
static void check_unaligned_access_emulated(void *arg __always_unused)
{
int cpu = smp_processor_id();
@@ -716,6 +716,10 @@ bool unaligned_ctl_available(void)
return unaligned_ctl;
}
#else
+static bool all_cpus_unaligned_scalar_access_emulated(void)
+{
+ return false;
+}
bool __init check_unaligned_access_emulated_all_cpus(void)
{
return false;
--
2.43.0
- Charlie
>
> Thanks,
>
> Clément
>
> >
> > - Charlie
> >
> >> + RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED)
> >> + return false;
> >> +
> >> + return true;
> >> +}
> >> +
> >> #ifdef CONFIG_RISCV_SCALAR_MISALIGNED
> >>
> >> static bool unaligned_ctl __read_mostly;
> >> @@ -685,8 +697,6 @@ static int
> >> cpu_online_check_unaligned_access_emulated(unsigned int cpu)
> >>
> >> bool __init check_unaligned_access_emulated_all_cpus(void)
> >> {
> >> - int cpu;
> >> -
> >> /*
> >> * We can only support PR_UNALIGN controls if all CPUs have misaligned
> >> * accesses emulated since tasks requesting such control can run on any
> >> @@ -694,10 +704,8 @@ bool __init
> >> check_unaligned_access_emulated_all_cpus(void)
> >> */
> >> on_each_cpu(check_unaligned_access_emulated, NULL, 1);
> >>
> >> - for_each_online_cpu(cpu)
> >> - if (per_cpu(misaligned_access_speed, cpu)
> >> - != RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED)
> >> - return false;
> >> + if (!all_cpus_unaligned_scalar_access_emulated())
> >> + return false;
> >>
> >> unaligned_ctl = true;
> >> return true;
> >> --
> >> 2.49.0
> >>
> >>
> >> _______________________________________________
> >> linux-riscv mailing list
> >> linux-ri...@lists.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/linux-riscv
>
