diff options
| -rw-r--r-- | arch/arm64/kernel/head.S | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 7ee6d74101cf..4b1abac3485a 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -525,10 +525,21 @@ set_hcr: msr hcr_el2, x0 isb - /* Generic timers. */ + /* + * Allow Non-secure EL1 and EL0 to access physical timer and counter. + * This is not necessary for VHE, since the host kernel runs in EL2, + * and EL0 accesses are configured in the later stage of boot process. + * Note that when HCR_EL2.E2H == 1, CNTHCTL_EL2 has the same bit layout + * as CNTKCTL_EL1, and CNTKCTL_EL1 accessing instructions are redefined + * to access CNTHCTL_EL2. This allows the kernel designed to run at EL1 + * to transparently mess with the EL0 bits via CNTKCTL_EL1 access in + * EL2. + */ + cbnz x2, 1f mrs x0, cnthctl_el2 orr x0, x0, #3 // Enable EL1 physical timers msr cnthctl_el2, x0 +1: msr cntvoff_el2, xzr // Clear virtual offset #ifdef CONFIG_ARM_GIC_V3 |
