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[PATCH v2 3/6] RISC-V: Check scalar unaligned access on all CPUs

Jesse Taube posted 6 patches 1 year, 8 months ago
There is a newer version of this series
[PATCH v2 3/6] RISC-V: Check scalar unaligned access on all CPUs
Posted by Jesse Taube 1 year, 8 months ago 
Originally, the check_unaligned_access_emulated_all_cpus function
only checked the boot hart. This fixes the function to check all
harts.

Check for Zicclsm before checking for unaligned access. This will
greatly reduce the boot up time as finding the access speed is no longer
necessary.

Signed-off-by: Jesse Taube <jesse@rivosinc.com>
---
V1 -> V2:
 - New patch
---
 arch/riscv/kernel/traps_misaligned.c       | 23 ++++++----------------
 arch/riscv/kernel/unaligned_access_speed.c | 23 +++++++++++++---------
 2 files changed, 20 insertions(+), 26 deletions(-)

diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index b62d5a2f4541..8fadbe00dd62 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -526,31 +526,17 @@ int handle_misaligned_store(struct pt_regs *regs)
 	return 0;
 }
 
-static bool check_unaligned_access_emulated(int cpu)
+static void check_unaligned_access_emulated(struct work_struct *unused)
 {
+	int cpu = smp_processor_id();
 	long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu);
 	unsigned long tmp_var, tmp_val;
-	bool misaligned_emu_detected;
 
 	*mas_ptr = RISCV_HWPROBE_MISALIGNED_UNKNOWN;
 
 	__asm__ __volatile__ (
 		"       "REG_L" %[tmp], 1(%[ptr])\n"
 		: [tmp] "=r" (tmp_val) : [ptr] "r" (&tmp_var) : "memory");
-
-	misaligned_emu_detected = (*mas_ptr == RISCV_HWPROBE_MISALIGNED_EMULATED);
-	/*
-	 * If unaligned_ctl is already set, this means that we detected that all
-	 * CPUS uses emulated misaligned access at boot time. If that changed
-	 * when hotplugging the new cpu, this is something we don't handle.
-	 */
-	if (unlikely(unaligned_ctl && !misaligned_emu_detected)) {
-		pr_crit("CPU misaligned accesses non homogeneous (expected all emulated)\n");
-		while (true)
-			cpu_relax();
-	}
-
-	return misaligned_emu_detected;
 }
 
 bool check_unaligned_access_emulated_all_cpus(void)
@@ -562,8 +548,11 @@ bool check_unaligned_access_emulated_all_cpus(void)
 	 * accesses emulated since tasks requesting such control can run on any
 	 * CPU.
 	 */
+	schedule_on_each_cpu(check_unaligned_access_emulated);
+
 	for_each_online_cpu(cpu)
-		if (!check_unaligned_access_emulated(cpu))
+		if (per_cpu(misaligned_access_speed, cpu)
+		    != RISCV_HWPROBE_MISALIGNED_EMULATED)
 			return false;
 
 	unaligned_ctl = true;
diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel/unaligned_access_speed.c
index a9a6bcb02acf..70c1588fc353 100644
--- a/arch/riscv/kernel/unaligned_access_speed.c
+++ b/arch/riscv/kernel/unaligned_access_speed.c
@@ -259,23 +259,28 @@ static int check_unaligned_access_speed_all_cpus(void)
 	kfree(bufs);
 	return 0;
 }
+#endif /* CONFIG_RISCV_PROBE_UNALIGNED_ACCESS */
 
 static int check_unaligned_access_all_cpus(void)
 {
-	bool all_cpus_emulated = check_unaligned_access_emulated_all_cpus();
+	bool all_cpus_emulated;
+	int cpu;
 
+	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_ZICCLSM)) {
+		for_each_online_cpu(cpu) {
+			per_cpu(misaligned_access_speed, cpu) = RISCV_HWPROBE_MISALIGNED_FAST;
+		}
+		return 0;
+	}
+
+	all_cpus_emulated = check_unaligned_access_emulated_all_cpus();
+
+#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS
 	if (!all_cpus_emulated)
 		return check_unaligned_access_speed_all_cpus();
+#endif
 
 	return 0;
 }
-#else /* CONFIG_RISCV_PROBE_UNALIGNED_ACCESS */
-static int check_unaligned_access_all_cpus(void)
-{
-	check_unaligned_access_emulated_all_cpus();
-
-	return 0;
-}
-#endif
 
 arch_initcall(check_unaligned_access_all_cpus);
-- 
2.43.0
Re: [PATCH v2 3/6] RISC-V: Check scalar unaligned access on all CPUs
Posted by Conor Dooley 1 year, 8 months ago 
On Thu, Jun 13, 2024 at 03:16:12PM -0400, Jesse Taube wrote:
> Originally, the check_unaligned_access_emulated_all_cpus function
> only checked the boot hart. This fixes the function to check all
> harts.

This seems like it should be split out and get a Fixes: tag & a cc:
stable.

> Check for Zicclsm before checking for unaligned access. This will
> greatly reduce the boot up time as finding the access speed is no longer
> necessary.
> 
> Signed-off-by: Jesse Taube <jesse@rivosinc.com>
> ---
> V1 -> V2:
>  - New patch
> ---
>  arch/riscv/kernel/traps_misaligned.c       | 23 ++++++----------------
>  arch/riscv/kernel/unaligned_access_speed.c | 23 +++++++++++++---------
>  2 files changed, 20 insertions(+), 26 deletions(-)
> 
> diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
> index b62d5a2f4541..8fadbe00dd62 100644
> --- a/arch/riscv/kernel/traps_misaligned.c
> +++ b/arch/riscv/kernel/traps_misaligned.c
> @@ -526,31 +526,17 @@ int handle_misaligned_store(struct pt_regs *regs)
>  	return 0;
>  }
>  
> -static bool check_unaligned_access_emulated(int cpu)
> +static void check_unaligned_access_emulated(struct work_struct *unused)
>  {
> +	int cpu = smp_processor_id();
>  	long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu);
>  	unsigned long tmp_var, tmp_val;
> -	bool misaligned_emu_detected;
>  
>  	*mas_ptr = RISCV_HWPROBE_MISALIGNED_UNKNOWN;
>  
>  	__asm__ __volatile__ (
>  		"       "REG_L" %[tmp], 1(%[ptr])\n"
>  		: [tmp] "=r" (tmp_val) : [ptr] "r" (&tmp_var) : "memory");
> -
> -	misaligned_emu_detected = (*mas_ptr == RISCV_HWPROBE_MISALIGNED_EMULATED);
> -	/*
> -	 * If unaligned_ctl is already set, this means that we detected that all
> -	 * CPUS uses emulated misaligned access at boot time. If that changed
> -	 * when hotplugging the new cpu, this is something we don't handle.
> -	 */
> -	if (unlikely(unaligned_ctl && !misaligned_emu_detected)) {
> -		pr_crit("CPU misaligned accesses non homogeneous (expected all emulated)\n");
> -		while (true)
> -			cpu_relax();
> -	}
> -
> -	return misaligned_emu_detected;
>  }
>  
>  bool check_unaligned_access_emulated_all_cpus(void)
> @@ -562,8 +548,11 @@ bool check_unaligned_access_emulated_all_cpus(void)
>  	 * accesses emulated since tasks requesting such control can run on any
>  	 * CPU.
>  	 */
> +	schedule_on_each_cpu(check_unaligned_access_emulated);
> +
>  	for_each_online_cpu(cpu)
> -		if (!check_unaligned_access_emulated(cpu))
> +		if (per_cpu(misaligned_access_speed, cpu)
> +		    != RISCV_HWPROBE_MISALIGNED_EMULATED)
>  			return false;
>  
>  	unaligned_ctl = true;
> diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel/unaligned_access_speed.c
> index a9a6bcb02acf..70c1588fc353 100644
> --- a/arch/riscv/kernel/unaligned_access_speed.c
> +++ b/arch/riscv/kernel/unaligned_access_speed.c
> @@ -259,23 +259,28 @@ static int check_unaligned_access_speed_all_cpus(void)
>  	kfree(bufs);
>  	return 0;
>  }
> +#endif /* CONFIG_RISCV_PROBE_UNALIGNED_ACCESS */
>  
>  static int check_unaligned_access_all_cpus(void)
>  {
> -	bool all_cpus_emulated = check_unaligned_access_emulated_all_cpus();
> +	bool all_cpus_emulated;
> +	int cpu;
>  
> +	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_ZICCLSM)) {
> +		for_each_online_cpu(cpu) {
> +			per_cpu(misaligned_access_speed, cpu) = RISCV_HWPROBE_MISALIGNED_FAST;
> +		}
> +		return 0;
> +	}
> +
> +	all_cpus_emulated = check_unaligned_access_emulated_all_cpus();
> +
> +#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS

Can we make this an IS_ENABLED() please?


Thanks,
Conor.

>  	if (!all_cpus_emulated)
>  		return check_unaligned_access_speed_all_cpus();
> +#endif
>  
>  	return 0;
>  }
> -#else /* CONFIG_RISCV_PROBE_UNALIGNED_ACCESS */
> -static int check_unaligned_access_all_cpus(void)
> -{
> -	check_unaligned_access_emulated_all_cpus();
> -
> -	return 0;
> -}
> -#endif
>  
>  arch_initcall(check_unaligned_access_all_cpus);
> -- 
> 2.43.0
>
Re: [PATCH v2 3/6] RISC-V: Check scalar unaligned access on all CPUs
Posted by Charlie Jenkins 1 year, 7 months ago 
On Fri, Jun 14, 2024 at 09:22:47AM +0100, Conor Dooley wrote:
> On Thu, Jun 13, 2024 at 03:16:12PM -0400, Jesse Taube wrote:
> > Originally, the check_unaligned_access_emulated_all_cpus function
> > only checked the boot hart. This fixes the function to check all
> > harts.
> 
> This seems like it should be split out and get a Fixes: tag & a cc:
> stable.

These changes are great Jesse! I agree with Conor, please split these
changes into two different patches with a fixes tag for
71c54b3d169d ("riscv: report misaligned accesses emulation to hwprobe").


- Charlie

> 
> > Check for Zicclsm before checking for unaligned access. This will
> > greatly reduce the boot up time as finding the access speed is no longer
> > necessary.
> > 
> > Signed-off-by: Jesse Taube <jesse@rivosinc.com>
> > ---
> > V1 -> V2:
> >  - New patch
> > ---
> >  arch/riscv/kernel/traps_misaligned.c       | 23 ++++++----------------
> >  arch/riscv/kernel/unaligned_access_speed.c | 23 +++++++++++++---------
> >  2 files changed, 20 insertions(+), 26 deletions(-)
> > 
> > diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
> > index b62d5a2f4541..8fadbe00dd62 100644
> > --- a/arch/riscv/kernel/traps_misaligned.c
> > +++ b/arch/riscv/kernel/traps_misaligned.c
> > @@ -526,31 +526,17 @@ int handle_misaligned_store(struct pt_regs *regs)
> >  	return 0;
> >  }
> >  
> > -static bool check_unaligned_access_emulated(int cpu)
> > +static void check_unaligned_access_emulated(struct work_struct *unused)
> >  {
> > +	int cpu = smp_processor_id();
> >  	long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu);
> >  	unsigned long tmp_var, tmp_val;
> > -	bool misaligned_emu_detected;
> >  
> >  	*mas_ptr = RISCV_HWPROBE_MISALIGNED_UNKNOWN;
> >  
> >  	__asm__ __volatile__ (
> >  		"       "REG_L" %[tmp], 1(%[ptr])\n"
> >  		: [tmp] "=r" (tmp_val) : [ptr] "r" (&tmp_var) : "memory");
> > -
> > -	misaligned_emu_detected = (*mas_ptr == RISCV_HWPROBE_MISALIGNED_EMULATED);
> > -	/*
> > -	 * If unaligned_ctl is already set, this means that we detected that all
> > -	 * CPUS uses emulated misaligned access at boot time. If that changed
> > -	 * when hotplugging the new cpu, this is something we don't handle.
> > -	 */
> > -	if (unlikely(unaligned_ctl && !misaligned_emu_detected)) {
> > -		pr_crit("CPU misaligned accesses non homogeneous (expected all emulated)\n");
> > -		while (true)
> > -			cpu_relax();
> > -	}
> > -
> > -	return misaligned_emu_detected;
> >  }
> >  
> >  bool check_unaligned_access_emulated_all_cpus(void)
> > @@ -562,8 +548,11 @@ bool check_unaligned_access_emulated_all_cpus(void)
> >  	 * accesses emulated since tasks requesting such control can run on any
> >  	 * CPU.
> >  	 */
> > +	schedule_on_each_cpu(check_unaligned_access_emulated);
> > +
> >  	for_each_online_cpu(cpu)
> > -		if (!check_unaligned_access_emulated(cpu))
> > +		if (per_cpu(misaligned_access_speed, cpu)
> > +		    != RISCV_HWPROBE_MISALIGNED_EMULATED)
> >  			return false;
> >  
> >  	unaligned_ctl = true;
> > diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel/unaligned_access_speed.c
> > index a9a6bcb02acf..70c1588fc353 100644
> > --- a/arch/riscv/kernel/unaligned_access_speed.c
> > +++ b/arch/riscv/kernel/unaligned_access_speed.c
> > @@ -259,23 +259,28 @@ static int check_unaligned_access_speed_all_cpus(void)
> >  	kfree(bufs);
> >  	return 0;
> >  }
> > +#endif /* CONFIG_RISCV_PROBE_UNALIGNED_ACCESS */
> >  
> >  static int check_unaligned_access_all_cpus(void)
> >  {
> > -	bool all_cpus_emulated = check_unaligned_access_emulated_all_cpus();
> > +	bool all_cpus_emulated;
> > +	int cpu;
> >  
> > +	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_ZICCLSM)) {
> > +		for_each_online_cpu(cpu) {
> > +			per_cpu(misaligned_access_speed, cpu) = RISCV_HWPROBE_MISALIGNED_FAST;
> > +		}
> > +		return 0;
> > +	}
> > +
> > +	all_cpus_emulated = check_unaligned_access_emulated_all_cpus();
> > +
> > +#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS
> 
> Can we make this an IS_ENABLED() please?
> 
> 
> Thanks,
> Conor.
> 
> >  	if (!all_cpus_emulated)
> >  		return check_unaligned_access_speed_all_cpus();
> > +#endif
> >  
> >  	return 0;
> >  }
> > -#else /* CONFIG_RISCV_PROBE_UNALIGNED_ACCESS */
> > -static int check_unaligned_access_all_cpus(void)
> > -{
> > -	check_unaligned_access_emulated_all_cpus();
> > -
> > -	return 0;
> > -}
> > -#endif
> >  
> >  arch_initcall(check_unaligned_access_all_cpus);
> > -- 
> > 2.43.0
> >

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