diff mbox series

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

Message ID 20190925025922.176362-2-justin.he@arm.com (mailing list archive)
State New, archived
Headers show
Series fix double page fault on arm64 | expand

Commit Message

Jia He Sept. 25, 2019, 2:59 a.m. UTC 
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 <justin.he@arm.com>
Suggested-by: Suzuki Poulose <Suzuki.Poulose@arm.com>
Reported-by: kbuild test robot <lkp@intel.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/include/asm/cpufeature.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

Comments

Catalin Marinas Sept. 25, 2019, 2:38 p.m. UTC | #1 
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 <justin.he@arm.com>
> Suggested-by: Suzuki Poulose <Suzuki.Poulose@arm.com>
> Reported-by: kbuild test robot <lkp@intel.com>

Which bug did the kbuild robot actually report? I'd drop this line.
Jia He Sept. 26, 2019, 9:23 a.m. UTC | #2 
Hi Catalin

> -----Original Message-----
> From: Catalin Marinas <catalin.marinas@arm.com>
> Sent: 2019年9月25日 22:38
> To: Justin He (Arm Technology China) <Justin.He@arm.com>
> Cc: Will Deacon <will@kernel.org>; Mark Rutland
> <Mark.Rutland@arm.com>; James Morse <James.Morse@arm.com>; Marc
> Zyngier <maz@kernel.org>; Matthew Wilcox <willy@infradead.org>; Kirill A.
> Shutemov <kirill.shutemov@linux.intel.com>; linux-arm-
> kernel@lists.infradead.org; linux-kernel@vger.kernel.org; linux-
> mm@kvack.org; Suzuki Poulose <Suzuki.Poulose@arm.com>; Punit
> Agrawal <punitagrawal@gmail.com>; Anshuman Khandual
> <Anshuman.Khandual@arm.com>; Alex Van Brunt
> <avanbrunt@nvidia.com>; Robin Murphy <Robin.Murphy@arm.com>;
> Thomas Gleixner <tglx@linutronix.de>; Andrew Morton <akpm@linux-
> foundation.org>; Jérôme Glisse <jglisse@redhat.com>; Ralph Campbell
> <rcampbell@nvidia.com>; hejianet@gmail.com; Kaly Xin (Arm Technology
> China) <Kaly.Xin@arm.com>; nd <nd@arm.com>
> 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 <justin.he@arm.com>
> > Suggested-by: Suzuki Poulose <Suzuki.Poulose@arm.com>
> > Reported-by: kbuild test robot <lkp@intel.com>
> 
> 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 <lkp@intel.com>"

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)
diff mbox series

Patch

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