| Message ID | 20180518114424.18054-2-alex.bennee@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | support reading of CNT[VCT|FRQ]_EL0 from user-space | expand |
On 18 May 2018 at 12:44, Alex Bennée <alex.bennee@linaro.org> wrote: > 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 <alex.bennee@linaro.org> > > --- > 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, You might as well just make this be .type = ARM_CP_CONST, since the CPU state field can never change. Also, perhaps NANOSECONDS_PER_SECOND / 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 > }; Do we need to make the 32-bit registers accessible to linux-user processes too? (Incidentally, another thing along these lines we should probably look at is that I think that newer kernels emulate ID register accesses from EL0, so we should do something to make those registers work too.) thanks -- PMM
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 };
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 <alex.bennee@linaro.org> --- v2 - include CNTFRQ_EL0 for PL0_R only --- target/arm/helper.c | 27 ++++++++++++++++++++++++--- 1 file changed, 24 insertions(+), 3 deletions(-) -- 2.17.0