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[Qemu-arm] [PATCH v2 1/2] target/arm: support reading of CNT[VCT|FRQ]_EL
From: |
Alex Bennée |
Subject: |
[Qemu-arm] [PATCH v2 1/2] target/arm: support reading of CNT[VCT|FRQ]_EL0 from user-space |
Date: |
Fri, 18 May 2018 12:44:23 +0100 |
Since kernel commit a86bd139f2 (arm64: arch_timer: Enable CNTVCT_EL0
trap..) 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().
Signed-off-by: Alex Bennée <address@hidden>
---
v2
- include CNTFRQ_EL0 for PL0_R only
---
target/arm/helper.c | 27 ++++++++++++++++++++++++---
1 file changed, 24 insertions(+), 3 deletions(-)
diff --git a/target/arm/helper.c b/target/arm/helper.c
index db8bbe52a6..39098a15bf 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -2135,11 +2135,32 @@ 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[] = {
+ { .name = "CNTFRQ_EL0", .state = ARM_CP_STATE_AA64,
+ .opc0 = 3, .opc1 = 3, .crn = 14, .crm = 0, .opc2 = 0,
+ .access = PL0_R /* no PL1_RW in linux-user */,
+ .fieldoffset = offsetof(CPUARMState, cp15.c14_cntfrq),
+ .resetvalue = (1000 * 1000 * 1000) / GTIMER_SCALE,
+ },
+ { .name = "CNTVCT_EL0", .state = ARM_CP_STATE_AA64,
+ .opc0 = 3, .opc1 = 3, .crn = 14, .crm = 0, .opc2 = 2,
+ .access = PL0_R, .type = ARM_CP_NO_RAW | ARM_CP_IO,
+ .readfn = gt_virt_cnt_read,
+ },
REGINFO_SENTINEL
};
--
2.17.0