Re: [PATCH v4 10/10] powerpc/watchpoint: Remove 512 byte boundary

[Ravi Bangoria]

Hi Jordan,

On 7/20/20 12:24 PM, Jordan Niethe wrote:

On Fri, Jul 17, 2020 at 2:11 PM Ravi Bangoria
 wrote:


Power10 has removed 512 bytes boundary from match criteria. i.e. The watch
range can cross 512 bytes boundary.

It looks like this change is not mentioned in ISA v3.1 Book III 9.4
Data Address Watchpoint. It could be useful to mention that in the
commit message.


Yes, ISA 3.1 Book III 9.4 has a documentation mistake and hopefully it
will be fixed in the next version of ISA. Though, this is mentioned in
ISA 3.1 change log:

  Multiple DEAW:
  Added a second Data Address Watchpoint. [H]DAR is
  set to the first byte of overlap. 512B boundary is
  removed.

I'll mention this in the commit description.


Also I wonder if could add a test for this to the ptrace-hwbreak selftest?


Yes, I already have a selftest for this in perf-hwbreak. Will send that soon.

Thanks,
Ravi

Re: [PATCH v4 10/10] powerpc/watchpoint: Remove 512 byte boundary

[Jordan Niethe]

On Fri, Jul 17, 2020 at 2:11 PM Ravi Bangoria
 wrote:
>
> Power10 has removed 512 bytes boundary from match criteria. i.e. The watch
> range can cross 512 bytes boundary.
It looks like this change is not mentioned in ISA v3.1 Book III 9.4
Data Address Watchpoint. It could be useful to mention that in the
commit message.
Also I wonder if could add a test for this to the ptrace-hwbreak selftest?

>
> Signed-off-by: Ravi Bangoria 
> ---
>  arch/powerpc/kernel/hw_breakpoint.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kernel/hw_breakpoint.c 
> b/arch/powerpc/kernel/hw_breakpoint.c
> index c55e67bab271..1f4a1efa0074 100644
> --- a/arch/powerpc/kernel/hw_breakpoint.c
> +++ b/arch/powerpc/kernel/hw_breakpoint.c
> @@ -418,8 +418,9 @@ static int hw_breakpoint_validate_len(struct 
> arch_hw_breakpoint *hw)
>
> if (dawr_enabled()) {
> max_len = DAWR_MAX_LEN;
> -   /* DAWR region can't cross 512 bytes boundary */
> -   if (ALIGN_DOWN(start_addr, SZ_512) != ALIGN_DOWN(end_addr - 
> 1, SZ_512))
> +   /* DAWR region can't cross 512 bytes boundary on p10 
> predecessors */
> +   if (!cpu_has_feature(CPU_FTR_ARCH_31) &&
> +   (ALIGN_DOWN(start_addr, SZ_512) != ALIGN_DOWN(end_addr - 
> 1, SZ_512)))
> return -EINVAL;
> } else if (IS_ENABLED(CONFIG_PPC_8xx)) {
> /* 8xx can setup a range without limitation */
> --
> 2.26.2
>

[PATCH v4 10/10] powerpc/watchpoint: Remove 512 byte boundary

[Ravi Bangoria]

Power10 has removed 512 bytes boundary from match criteria. i.e. The watch
range can cross 512 bytes boundary.

Signed-off-by: Ravi Bangoria 
---
 arch/powerpc/kernel/hw_breakpoint.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/hw_breakpoint.c 
b/arch/powerpc/kernel/hw_breakpoint.c
index c55e67bab271..1f4a1efa0074 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -418,8 +418,9 @@ static int hw_breakpoint_validate_len(struct 
arch_hw_breakpoint *hw)
 
if (dawr_enabled()) {
max_len = DAWR_MAX_LEN;
-   /* DAWR region can't cross 512 bytes boundary */
-   if (ALIGN_DOWN(start_addr, SZ_512) != ALIGN_DOWN(end_addr - 1, 
SZ_512))
+   /* DAWR region can't cross 512 bytes boundary on p10 
predecessors */
+   if (!cpu_has_feature(CPU_FTR_ARCH_31) &&
+   (ALIGN_DOWN(start_addr, SZ_512) != ALIGN_DOWN(end_addr - 1, 
SZ_512)))
return -EINVAL;
} else if (IS_ENABLED(CONFIG_PPC_8xx)) {
/* 8xx can setup a range without limitation */
-- 
2.26.2