The current handling of erratum 1414080 has the side effect that cntkctl_el1 can get changed for both 32 and 64bit tasks.
This isn't a problem so far, but if we ever need to mitigate another of these errata on the 64bit side, we'd better keep the messing with cntkctl_el1 local to 32bit tasks. For that, make sure that on entering the kernel from a 32bit tasks, userspace access to cntvct gets enabled, and disabled returning to userspace, while it never gets changed for 64bit tasks. Signed-off-by: Marc Zyngier <[email protected]> --- arch/arm64/kernel/entry.S | 40 +++++++++++++++++++++++---------------- 1 file changed, 24 insertions(+), 16 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 5304d193c79d..8f51f3273bc7 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -167,6 +167,19 @@ alternative_cb_end stp x28, x29, [sp, #16 * 14] .if \el == 0 + .if \regsize == 32 + // If we come back from a 32bit task on a system affected by + // 1418040, let's reenable userspace access to the virtual counter. +#ifdef CONFIG_ARM64_ERRATUM_1418040 +alternative_if_not ARM64_WORKAROUND_1418040 + b .L__entry_skip_wa_1418040\@ +alternative_else_nop_endif + mrs x0, cntkctl_el1 + orr x0, x0, #2 // ARCH_TIMER_USR_VCT_ACCESS_EN + msr cntkctl_el1, x0 +.L__entry_skip_wa_1418040\@: +#endif + .endif clear_gp_regs mrs x21, sp_el0 ldr_this_cpu tsk, __entry_task, x20 @@ -318,7 +331,17 @@ alternative_else_nop_endif ldr x23, [sp, #S_SP] // load return stack pointer msr sp_el0, x23 tst x22, #PSR_MODE32_BIT // native task? - b.eq 3f + b.eq 4f + +#ifdef CONFIG_ARM64_ERRATUM_1418040 +alternative_if_not ARM64_WORKAROUND_1418040 + b 3f +alternative_else_nop_endif + mrs x1, cntkctl_el1 + bic x1, x1, #2 // ARCH_TIMER_USR_VCT_ACCESS_EN + msr cntkctl_el1, x1 +3: +#endif #ifdef CONFIG_ARM64_ERRATUM_845719 alternative_if ARM64_WORKAROUND_845719 @@ -330,22 +353,7 @@ alternative_if ARM64_WORKAROUND_845719 #endif alternative_else_nop_endif #endif -3: -#ifdef CONFIG_ARM64_ERRATUM_1418040 -alternative_if_not ARM64_WORKAROUND_1418040 - b 4f -alternative_else_nop_endif - /* - * if (x22.mode32 == cntkctl_el1.el0vcten) - * cntkctl_el1.el0vcten = ~cntkctl_el1.el0vcten - */ - mrs x1, cntkctl_el1 - eon x0, x1, x22, lsr #3 - tbz x0, #1, 4f - eor x1, x1, #2 // ARCH_TIMER_USR_VCT_ACCESS_EN - msr cntkctl_el1, x1 4: -#endif scs_save tsk, x0 /* No kernel C function calls after this as user keys are set. */ -- 2.27.0
