arm64: compat: Fix __arch_get_hw_counter() implementation
authorVincenzo Frascino <vincenzo.frascino@arm.com>
Tue, 25 Jun 2019 16:18:04 +0000 (17:18 +0100)
committerThomas Gleixner <tglx@linutronix.de>
Wed, 26 Jun 2019 12:26:54 +0000 (14:26 +0200)
commit6241c4dc6ec56a7627b972959da8b492b765b209
tree8fab8e0b34a38804d8f11a5a0b75a59ca1a048a4
parent27e11a9fe2e2e7e0d13f854e89a71e488678fb17
arm64: compat: Fix __arch_get_hw_counter() implementation

Provide the following fixes for the __arch_get_hw_counter()
implementation on arm64:
- Fallback on syscall when an unstable counter is detected.
- Introduce isb()s before and after the counter read to avoid
speculation of the counter value and of the seq lock
respectively.
The second isb() is a temporary solution that will be revisited
in 5.3-rc1.

These fixes restore the semantics that __arch_counter_get_cntvct()
had on arm64.

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mips@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Cc: catalin.marinas@arm.com
Cc: will.deacon@arm.com
Cc: arnd@arndb.de
Cc: linux@armlinux.org.uk
Cc: ralf@linux-mips.org
Cc: paul.burton@mips.com
Cc: daniel.lezcano@linaro.org
Cc: salyzyn@android.com
Cc: pcc@google.com
Cc: shuah@kernel.org
Cc: 0x7f454c46@gmail.com
Cc: linux@rasmusvillemoes.dk
Cc: huw@codeweavers.com
Cc: sthotton@marvell.com
Cc: andre.przywara@arm.com
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/20190625161804.38713-3-vincenzo.frascino@arm.com
arch/arm64/include/asm/vdso/compat_gettimeofday.h