RE: [PATCH v9 1/3] arm64: cpufeature: introduce helper cpu_has_hw_af()

[Justin He (Arm Technology China)]

Hi Catalin

> -Original Message-
> From: Catalin Marinas 
> Sent: 2019年9月25日 22:38
> To: Justin He (Arm Technology China) 
> Cc: Will Deacon ; Mark Rutland
> ; James Morse ; Marc
> Zyngier ; Matthew Wilcox ; Kirill A.
> Shutemov ; linux-arm-
> ker...@lists.infradead.org; linux-kernel@vger.kernel.org; linux-
> m...@kvack.org; Suzuki Poulose ; Punit
> Agrawal ; Anshuman Khandual
> ; Alex Van Brunt
> ; Robin Murphy ;
> Thomas Gleixner ; Andrew Morton  foundation.org>; Jérôme Glisse ; Ralph Campbell
> ; hejia...@gmail.com; Kaly Xin (Arm Technology
> China) ; nd 
> Subject: Re: [PATCH v9 1/3] arm64: cpufeature: introduce helper
> cpu_has_hw_af()
> 
> On Wed, Sep 25, 2019 at 10:59:20AM +0800, Jia He wrote:
> > We unconditionally set the HW_AFDBM capability and only enable it on
> > CPUs which really have the feature. But sometimes we need to know
> > whether this cpu has the capability of HW AF. So decouple AF from
> > DBM by new helper cpu_has_hw_af().
> >
> > Signed-off-by: Jia He 
> > Suggested-by: Suzuki Poulose 
> > Reported-by: kbuild test robot 
> 
> Which bug did the kbuild robot actually report? I'd drop this line.
> 
This line is added due to [1]:
"If you fix the issue, kindly add following tag
Reported-by: kbuild test robot "

Yes, I know your concern, it is a little bit confusing. But I don't know
how to distinguish the case btw a) original bug report b) bug report
of my patch implementation? Thanks for any suggestion.

[1] https://www.lkml.org/lkml/2019/9/18/940


--
Cheers,
Justin (Jia He)

Re: [PATCH v9 1/3] arm64: cpufeature: introduce helper cpu_has_hw_af()

[Catalin Marinas]

On Wed, Sep 25, 2019 at 10:59:20AM +0800, Jia He wrote:
> We unconditionally set the HW_AFDBM capability and only enable it on
> CPUs which really have the feature. But sometimes we need to know
> whether this cpu has the capability of HW AF. So decouple AF from
> DBM by new helper cpu_has_hw_af().
> 
> Signed-off-by: Jia He 
> Suggested-by: Suzuki Poulose 
> Reported-by: kbuild test robot 

Which bug did the kbuild robot actually report? I'd drop this line.

-- 
Catalin

[PATCH v9 1/3] arm64: cpufeature: introduce helper cpu_has_hw_af()

[Jia He]

We unconditionally set the HW_AFDBM capability and only enable it on
CPUs which really have the feature. But sometimes we need to know
whether this cpu has the capability of HW AF. So decouple AF from
DBM by new helper cpu_has_hw_af().

Signed-off-by: Jia He 
Suggested-by: Suzuki Poulose 
Reported-by: kbuild test robot 
Reviewed-by: Catalin Marinas 
---
 arch/arm64/include/asm/cpufeature.h | 10 ++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/include/asm/cpufeature.h 
b/arch/arm64/include/asm/cpufeature.h
index c96ffa4722d3..c2e3abd39faa 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -667,6 +667,16 @@ static inline u32 id_aa64mmfr0_parange_to_phys_shift(int 
parange)
default: return CONFIG_ARM64_PA_BITS;
}
 }
+
+/* Check whether hardware update of the Access flag is supported */
+static inline bool cpu_has_hw_af(void)
+{
+   if (IS_ENABLED(CONFIG_ARM64_HW_AFDBM))
+   return read_cpuid(ID_AA64MMFR1_EL1) & 0xf;
+
+   return false;
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif
-- 
2.17.1