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arm64: Add CNT{P,V}CTSS_EL0 alternatives to cnt{p,v}ct_el0 

CNTPCTSS_EL0 and CNTVCTSS_EL0 are alternatives to the usual
CNTPCT_EL0 and CNTVCT_EL0 that do not require a previous ISB
to be synchronised (SS stands for Self-Synchronising).

Use the ARM64_HAS_ECV capability to control alternative sequences
that switch to these low(er)-cost primitives. Note that the
counter access in the VDSO is for now left alone until we decide
whether we want to allow this.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211017124225.3018098-16-maz@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Marc Zyngier 2021-10-17 13:42:23 +01:00 committed by Will Deacon
parent fdf865988b
commit 9ee840a960
2 changed files with 27 additions and 8 deletions
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32
arch/arm64/include/asm/arch_timer.h
View File

@ -64,14 +64,26 @@ DECLARE_PER_CPU(const struct arch_timer_erratum_workaround *,
static inline notrace u64 arch_timer_read_cntpct_el0(void)
{
isb();
return read_sysreg(cntpct_el0);
u64 cnt;
asm volatile(ALTERNATIVE("isb\n mrs %0, cntpct_el0",
"nop\n" __mrs_s("%0", SYS_CNTPCTSS_EL0),
ARM64_HAS_ECV)
: "=r" (cnt));
return cnt;
}
static inline notrace u64 arch_timer_read_cntvct_el0(void)
{
isb();
return read_sysreg(cntvct_el0);
u64 cnt;
asm volatile(ALTERNATIVE("isb\n mrs %0, cntvct_el0",
"nop\n" __mrs_s("%0", SYS_CNTVCTSS_EL0),
ARM64_HAS_ECV)
: "=r" (cnt));
return cnt;
}
#define arch_timer_reg_read_stable(reg) \
@ -174,8 +186,10 @@ static __always_inline u64 __arch_counter_get_cntpct(void)
{
u64 cnt;
isb();
cnt = read_sysreg(cntpct_el0);
asm volatile(ALTERNATIVE("isb\n mrs %0, cntpct_el0",
"nop\n" __mrs_s("%0", SYS_CNTPCTSS_EL0),
ARM64_HAS_ECV)
: "=r" (cnt));
arch_counter_enforce_ordering(cnt);
return cnt;
}
@ -193,8 +207,10 @@ static __always_inline u64 __arch_counter_get_cntvct(void)
{
u64 cnt;
isb();
cnt = read_sysreg(cntvct_el0);
asm volatile(ALTERNATIVE("isb\n mrs %0, cntvct_el0",
"nop\n" __mrs_s("%0", SYS_CNTVCTSS_EL0),
ARM64_HAS_ECV)
: "=r" (cnt));
arch_counter_enforce_ordering(cnt);
return cnt;
}

3
arch/arm64/include/asm/sysreg.h
View File

@ -507,6 +507,9 @@
#define SYS_CNTFRQ_EL0 sys_reg(3, 3, 14, 0, 0)
#define SYS_CNTPCTSS_EL0 sys_reg(3, 3, 14, 0, 5)
#define SYS_CNTVCTSS_EL0 sys_reg(3, 3, 14, 0, 6)
#define SYS_CNTP_TVAL_EL0 sys_reg(3, 3, 14, 2, 0)
#define SYS_CNTP_CTL_EL0 sys_reg(3, 3, 14, 2, 1)
#define SYS_CNTP_CVAL_EL0 sys_reg(3, 3, 14, 2, 2)