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target/arm: support reading of CNT[VCT|FRQ]_EL0 from user-space

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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
This commit is contained in:
Alex Bennée 2018-07-03 04:59:56 -04:00 committed by Lioncash
parent a325de6685
commit 85512a5121
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GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 19 additions and 3 deletions
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22
qemu/target/arm/helper.c
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@ -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
};