Commit 5c13f042 authored by Joey Gouly's avatar Joey Gouly Committed by Catalin Marinas
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arm64: cpufeature: add HWCAP for FEAT_AFP 



Add a new HWCAP to detect the Alternate Floating-point Behaviour
feature (FEAT_AFP), introduced in Armv8.7.

Also expose this to userspace in the ID_AA64MMFR1_EL1 feature register.

Signed-off-by: default avatarJoey Gouly <joey.gouly@arm.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211210165432.8106-2-joey.gouly@arm.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent d58071a8

Documentation/arm64/cpu-feature-registers.rst

+9 −0
Original line number Diff line number Diff line
@@ -275,6 +275,15 @@ infrastructure: 
     | SVEVer                       | [3-0]   |    y    |

     +------------------------------+---------+---------+



  8) ID_AA64MMFR1_EL1 - Memory model feature register 1



     +------------------------------+---------+---------+

     | Name                         |  bits   | visible |

     +------------------------------+---------+---------+

     | AFP                          | [47-44] |    y    |

     +------------------------------+---------+---------+





Appendix I: Example

-------------------

Documentation/arm64/elf_hwcaps.rst

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@@ -251,6 +251,10 @@ HWCAP2_ECV 


    Functionality implied by ID_AA64MMFR0_EL1.ECV == 0b0001.



HWCAP2_AFP



    Functionality implied by ID_AA64MFR1_EL1.AFP == 0b0001.



4. Unused AT_HWCAP bits

-----------------------

arch/arm64/include/asm/hwcap.h

+1 −0
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@@ -106,6 +106,7 @@ 
#define KERNEL_HWCAP_BTI		__khwcap2_feature(BTI)

#define KERNEL_HWCAP_MTE		__khwcap2_feature(MTE)

#define KERNEL_HWCAP_ECV		__khwcap2_feature(ECV)

#define KERNEL_HWCAP_AFP		__khwcap2_feature(AFP)



/*

 * This yields a mask that user programs can use to figure out what

arch/arm64/include/asm/sysreg.h

+1 −0
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@@ -889,6 +889,7 @@ 
#endif



/* id_aa64mmfr1 */

#define ID_AA64MMFR1_AFP_SHIFT		44

#define ID_AA64MMFR1_ETS_SHIFT		36

#define ID_AA64MMFR1_TWED_SHIFT		32

#define ID_AA64MMFR1_XNX_SHIFT		28

arch/arm64/include/uapi/asm/hwcap.h

+1 −0
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@@ -76,5 +76,6 @@ 
#define HWCAP2_BTI		(1 << 17)

#define HWCAP2_MTE		(1 << 18)

#define HWCAP2_ECV		(1 << 19)

#define HWCAP2_AFP		(1 << 20)



#endif /* _UAPI__ASM_HWCAP_H */