Re: [PATCH v4 19/29] arm64: enable PKEY support for CPUs with S1POE

On Tue, Jul 16, 2024 at 04:17:12PM +0530, Anshuman Khandual wrote:

On 5/3/24 18:31, Joey Gouly wrote:

quoted

Now that PKEYs support has been implemented, enable it for CPUs that
support S1POE.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>

Reviewed-by: Anshuman Khandual <redacted>

quoted

---
 arch/arm64/include/asm/pkeys.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/pkeys.h b/arch/arm64/include/asm/pkeys.h
index a284508a4d02..3ea928ec94c0 100644
--- a/arch/arm64/include/asm/pkeys.h
+++ b/arch/arm64/include/asm/pkeys.h

@@ -17,7 +17,7 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 
 static inline bool arch_pkeys_enabled(void)
 {
-	return false;
+	return system_supports_poe();
 }
 
 static inline int vma_pkey(struct vm_area_struct *vma)

Small nit. Would it better to be consistently using system_supports_poe()
helper rather than arch_pkeys_enabled() inside arch/arm64/ platform code
like - during POE fault handling i.e inside fault_from_pkey().

(FWIW, arch_pkeys_enabled() looks like the hook for the arch to tell
the pkeys generic code whether the arch support is there, so I guess
the proposed change looks sensible to me.

For the arch backend code that is agnostic to whether pkeys is actually
in use, system_supports_poe() seems to be the more appropriate check.)

Cheers
---Dave