arm64: generic timer: use virtual counter instead of physical at EL0
We want to use the virtual counter at EL0, as the physical counter
may not track the current clocksource for guests running under a
hypervisor.
This patch updates the vdso and generic timer driver to use the virtual
counter. The kernel EL2 entry code is also updated to ensure that the
virtual offset is initialised to zero.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm64/include/asm/arm_generic.h b/arch/arm64/include/asm/arm_generic.h
index e4cec9d..df2aeb8 100644
--- a/arch/arm64/include/asm/arm_generic.h
+++ b/arch/arm64/include/asm/arm_generic.h
@@ -70,12 +70,12 @@
{
u32 cntkctl;
- /* Disable user access to the timers and the virtual counter. */
+ /* Disable user access to the timers and the physical counter. */
asm volatile("mrs %0, cntkctl_el1" : "=r" (cntkctl));
- cntkctl &= ~((3 << 8) | (1 << 1));
+ cntkctl &= ~((3 << 8) | (1 << 0));
- /* Enable user access to the physical counter and frequency. */
- cntkctl |= 1;
+ /* Enable user access to the virtual counter and frequency. */
+ cntkctl |= (1 << 1);
asm volatile("msr cntkctl_el1, %0" : : "r" (cntkctl));
}
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index a2f02b6..90dec55 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -158,6 +158,7 @@
mrs x0, cnthctl_el2
orr x0, x0, #3 // Enable EL1 physical timers
msr cnthctl_el2, x0
+ msr cntvoff_el2, xzr // Clear virtual offset
/* Populate ID registers. */
mrs x0, midr_el1
diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S
index 6681f40..8bf658d 100644
--- a/arch/arm64/kernel/vdso/gettimeofday.S
+++ b/arch/arm64/kernel/vdso/gettimeofday.S
@@ -220,9 +220,9 @@
ldp w11, w12, [vdso_data, #VDSO_CS_MULT]
seqcnt_read w9
- /* Read the physical counter. */
+ /* Read the virtual counter. */
isb
- mrs x15, cntpct_el0
+ mrs x15, cntvct_el0
/* Calculate cycle delta and convert to ns. */
sub x10, x15, x10