From 85512a512131eba7e63e192d266e0ca7a916a0d3 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Alex=20Benn=C3=A9e?= Date: Tue, 3 Jul 2018 04:59:56 -0400 Subject: [PATCH] target/arm: support reading of CNT[VCT|FRQ]_EL0 from user-space Since kernel commit a86bd139f2 (arm64: arch_timer: Enable CNTVCT_EL0 trap..), released in kernel version v4.12, user-space has been able to read these system registers. As we can't use QEMUTimer's in linux-user mode we just directly call cpu_get_clock(). Backports commit 26c4a83bd4707797868174332a540f7d61288d15 from qemu --- qemu/target/arm/helper.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/qemu/target/arm/helper.c b/qemu/target/arm/helper.c index a778f769..951c0254 100644 --- a/qemu/target/arm/helper.c +++ b/qemu/target/arm/helper.c @@ -1889,11 +1889,27 @@ static const ARMCPRegInfo generic_timer_cp_reginfo[] = { }; #else -/* In user-mode none of the generic timer registers are accessible, - * and their implementation depends on QEMU_CLOCK_VIRTUAL and qdev gpio outputs, - * so instead just don't register any of them. +/* In user-mode most of the generic timer registers are inaccessible + * however modern kernels (4.12+) allow access to cntvct_el0 */ + +static uint64_t gt_virt_cnt_read(CPUARMState *env, const ARMCPRegInfo *ri) +{ + /* Currently we have no support for QEMUTimer in linux-user so we + * can't call gt_get_countervalue(env), instead we directly + * call the lower level functions. + */ + return cpu_get_clock() / GTIMER_SCALE; +} + static const ARMCPRegInfo generic_timer_cp_reginfo[] = { + { "CNTFRQ_EL0", 0,14,0, 3,3,0, ARM_CP_STATE_AA64, + ARM_CP_CONST, PL0_R /* no PL1_RW in linux-user */, 0, NULL, NANOSECONDS_PER_SECOND / GTIMER_SCALE, + offsetof(CPUARMState, cp15.c14_cntfrq), + }, + { "CNTVCT_EL0", 0,14,0, 3,3,2, ARM_CP_STATE_AA64, ARM_CP_NO_RAW | ARM_CP_IO, + PL0_R, 0, NULL, 0, 0, 0, NULL, gt_virt_cnt_read, + }, REGINFO_SENTINEL };