| Message ID | 20191128054527.25450-3-andrew@aj.id.au (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Expose GT CNTFRQ as a CPU property to support AST2600 | expand |
On 28/11/2019 06:45, Andrew Jeffery wrote: > Prepare for SoCs such as the ASPEED AST2600 whose firmware configures > CNTFRQ to values significantly larger than the static 62.5MHz value > currently derived from GTIMER_SCALE. As the OS potentially derives its > timer periods from the CNTFRQ value the lack of support for running > QEMUTimers at the appropriate rate leads to sticky behaviour in the > guest. > > Substitute the GTIMER_SCALE constant with use of a helper to derive the > period from gt_cntfrq stored in struct ARMCPU. Initially set gt_cntfrq > to the frequency associated with GTIMER_SCALE so current behaviour is > maintained. > > Signed-off-by: Andrew Jeffery <andrew@aj.id.au> > --- > target/arm/cpu.c | 2 ++ > target/arm/cpu.h | 10 ++++++++++ > target/arm/helper.c | 10 +++++++--- > 3 files changed, 19 insertions(+), 3 deletions(-) > > diff --git a/target/arm/cpu.c b/target/arm/cpu.c > index 7a4ac9339bf9..5698a74061bb 100644 > --- a/target/arm/cpu.c > +++ b/target/arm/cpu.c > @@ -974,6 +974,8 @@ static void arm_cpu_initfn(Object *obj) > if (tcg_enabled()) { > cpu->psci_version = 2; /* TCG implements PSCI 0.2 */ > } > + > + cpu->gt_cntfrq = NANOSECONDS_PER_SECOND / GTIMER_SCALE; > } > > static Property arm_cpu_reset_cbar_property = > diff --git a/target/arm/cpu.h b/target/arm/cpu.h > index 83a809d4bac4..666c03871fdf 100644 > --- a/target/arm/cpu.h > +++ b/target/arm/cpu.h > @@ -932,8 +932,18 @@ struct ARMCPU { > */ > DECLARE_BITMAP(sve_vq_map, ARM_MAX_VQ); > DECLARE_BITMAP(sve_vq_init, ARM_MAX_VQ); > + > + /* Generic timer counter frequency, in Hz */ > + uint64_t gt_cntfrq; > }; > > +static inline unsigned int gt_cntfrq_period_ns(ARMCPU *cpu) > +{ > + /* XXX: Could include qemu/timer.h to get NANOSECONDS_PER_SECOND? */ > + const unsigned int ns_per_s = 1000 * 1000 * 1000; > + return ns_per_s > cpu->gt_cntfrq ? ns_per_s / cpu->gt_cntfrq : 1; > +} Are you inlining this helper for performance reasons ? C. > void arm_cpu_post_init(Object *obj); > > uint64_t arm_cpu_mp_affinity(int idx, uint8_t clustersz); > diff --git a/target/arm/helper.c b/target/arm/helper.c > index 65c4441a3896..1cc0551081a0 100644 > --- a/target/arm/helper.c > +++ b/target/arm/helper.c > @@ -2409,7 +2409,9 @@ static CPAccessResult gt_stimer_access(CPUARMState *env, > > static uint64_t gt_get_countervalue(CPUARMState *env) > { > - return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / GTIMER_SCALE; > + ARMCPU *cpu = env_archcpu(env); > + > + return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / gt_cntfrq_period_ns(cpu); > } > > static void gt_recalc_timer(ARMCPU *cpu, int timeridx) > @@ -2445,7 +2447,7 @@ static void gt_recalc_timer(ARMCPU *cpu, int timeridx) > * set the timer for as far in the future as possible. When the > * timer expires we will reset the timer for any remaining period. > */ > - if (nexttick > INT64_MAX / GTIMER_SCALE) { > + if (nexttick > INT64_MAX / gt_cntfrq_period_ns(cpu)) { > timer_mod_ns(cpu->gt_timer[timeridx], INT64_MAX); > } else { > timer_mod(cpu->gt_timer[timeridx], nexttick); > @@ -2874,11 +2876,13 @@ static const ARMCPRegInfo generic_timer_cp_reginfo[] = { > > static uint64_t gt_virt_cnt_read(CPUARMState *env, const ARMCPRegInfo *ri) > { > + ARMCPU *cpu = env_archcpu(env); > + > /* 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; > + return cpu_get_clock() / gt_cntfrq_period(cpu); > } > > static const ARMCPRegInfo generic_timer_cp_reginfo[] = { >
On Thu, 28 Nov 2019, at 19:16, Cédric Le Goater wrote: > On 28/11/2019 06:45, Andrew Jeffery wrote: > > Prepare for SoCs such as the ASPEED AST2600 whose firmware configures > > CNTFRQ to values significantly larger than the static 62.5MHz value > > currently derived from GTIMER_SCALE. As the OS potentially derives its > > timer periods from the CNTFRQ value the lack of support for running > > QEMUTimers at the appropriate rate leads to sticky behaviour in the > > guest. > > > > Substitute the GTIMER_SCALE constant with use of a helper to derive the > > period from gt_cntfrq stored in struct ARMCPU. Initially set gt_cntfrq > > to the frequency associated with GTIMER_SCALE so current behaviour is > > maintained. > > > > Signed-off-by: Andrew Jeffery <andrew@aj.id.au> > > --- > > target/arm/cpu.c | 2 ++ > > target/arm/cpu.h | 10 ++++++++++ > > target/arm/helper.c | 10 +++++++--- > > 3 files changed, 19 insertions(+), 3 deletions(-) > > > > diff --git a/target/arm/cpu.c b/target/arm/cpu.c > > index 7a4ac9339bf9..5698a74061bb 100644 > > --- a/target/arm/cpu.c > > +++ b/target/arm/cpu.c > > @@ -974,6 +974,8 @@ static void arm_cpu_initfn(Object *obj) > > if (tcg_enabled()) { > > cpu->psci_version = 2; /* TCG implements PSCI 0.2 */ > > } > > + > > + cpu->gt_cntfrq = NANOSECONDS_PER_SECOND / GTIMER_SCALE; > > } > > > > static Property arm_cpu_reset_cbar_property = > > diff --git a/target/arm/cpu.h b/target/arm/cpu.h > > index 83a809d4bac4..666c03871fdf 100644 > > --- a/target/arm/cpu.h > > +++ b/target/arm/cpu.h > > @@ -932,8 +932,18 @@ struct ARMCPU { > > */ > > DECLARE_BITMAP(sve_vq_map, ARM_MAX_VQ); > > DECLARE_BITMAP(sve_vq_init, ARM_MAX_VQ); > > + > > + /* Generic timer counter frequency, in Hz */ > > + uint64_t gt_cntfrq; > > }; > > > > +static inline unsigned int gt_cntfrq_period_ns(ARMCPU *cpu) > > +{ > > + /* XXX: Could include qemu/timer.h to get NANOSECONDS_PER_SECOND? */ > > + const unsigned int ns_per_s = 1000 * 1000 * 1000; > > + return ns_per_s > cpu->gt_cntfrq ? ns_per_s / cpu->gt_cntfrq : 1; > > +} > > Are you inlining this helper for performance reasons ? Originally I was going to do it as a macro in order to avoid redundantly scattering the calculation around. My thought was to use a macro as it's a simple calculation, but then figured it was a bit nicer as a function for type safety. I already had it as a macro in the header, so it was the least effort to switch it to a static inline and leave it where it was :) So that's the justification, mostly just evolution of thought process. Performance was also a consideration but I've done no measurements. Andrew
On Thu, 28 Nov 2019 at 05:44, Andrew Jeffery <andrew@aj.id.au> wrote: > > Prepare for SoCs such as the ASPEED AST2600 whose firmware configures > CNTFRQ to values significantly larger than the static 62.5MHz value > currently derived from GTIMER_SCALE. As the OS potentially derives its > timer periods from the CNTFRQ value the lack of support for running > QEMUTimers at the appropriate rate leads to sticky behaviour in the > guest. > > Substitute the GTIMER_SCALE constant with use of a helper to derive the > period from gt_cntfrq stored in struct ARMCPU. Initially set gt_cntfrq > to the frequency associated with GTIMER_SCALE so current behaviour is > maintained. > > Signed-off-by: Andrew Jeffery <andrew@aj.id.au> > +static inline unsigned int gt_cntfrq_period_ns(ARMCPU *cpu) > +{ > + /* XXX: Could include qemu/timer.h to get NANOSECONDS_PER_SECOND? */ > + const unsigned int ns_per_s = 1000 * 1000 * 1000; > + return ns_per_s > cpu->gt_cntfrq ? ns_per_s / cpu->gt_cntfrq : 1; > +} This function is named gt_cntfrq_period_ns()... > static uint64_t gt_virt_cnt_read(CPUARMState *env, const ARMCPRegInfo *ri) > { > + ARMCPU *cpu = env_archcpu(env); > + > /* 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; > + return cpu_get_clock() / gt_cntfrq_period(cpu); > } ...but here we call gt_cntfrq_period(), which doesn't exist, and indeed at least one of the patchew build systems reported it as a compile failure. thanks -- PMM
On Tue, 3 Dec 2019, at 04:42, Peter Maydell wrote: > On Thu, 28 Nov 2019 at 05:44, Andrew Jeffery <andrew@aj.id.au> wrote: > > > > Prepare for SoCs such as the ASPEED AST2600 whose firmware configures > > CNTFRQ to values significantly larger than the static 62.5MHz value > > currently derived from GTIMER_SCALE. As the OS potentially derives its > > timer periods from the CNTFRQ value the lack of support for running > > QEMUTimers at the appropriate rate leads to sticky behaviour in the > > guest. > > > > Substitute the GTIMER_SCALE constant with use of a helper to derive the > > period from gt_cntfrq stored in struct ARMCPU. Initially set gt_cntfrq > > to the frequency associated with GTIMER_SCALE so current behaviour is > > maintained. > > > > Signed-off-by: Andrew Jeffery <andrew@aj.id.au> > > > +static inline unsigned int gt_cntfrq_period_ns(ARMCPU *cpu) > > +{ > > + /* XXX: Could include qemu/timer.h to get NANOSECONDS_PER_SECOND? */ > > + const unsigned int ns_per_s = 1000 * 1000 * 1000; > > + return ns_per_s > cpu->gt_cntfrq ? ns_per_s / cpu->gt_cntfrq : 1; > > +} > > This function is named gt_cntfrq_period_ns()... > > > static uint64_t gt_virt_cnt_read(CPUARMState *env, const ARMCPRegInfo *ri) > > { > > + ARMCPU *cpu = env_archcpu(env); > > + > > /* 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; > > + return cpu_get_clock() / gt_cntfrq_period(cpu); > > } > > ...but here we call gt_cntfrq_period(), which doesn't exist, > and indeed at least one of the patchew build systems reported > it as a compile failure. > Ah yep, I failed to test user mode after renaming the function and missed this. I haven't seen an alert from patchew though, I wonder where that got to? Andrew
diff --git a/target/arm/cpu.c b/target/arm/cpu.c index 7a4ac9339bf9..5698a74061bb 100644 --- a/target/arm/cpu.c +++ b/target/arm/cpu.c @@ -974,6 +974,8 @@ static void arm_cpu_initfn(Object *obj) if (tcg_enabled()) { cpu->psci_version = 2; /* TCG implements PSCI 0.2 */ } + + cpu->gt_cntfrq = NANOSECONDS_PER_SECOND / GTIMER_SCALE; } static Property arm_cpu_reset_cbar_property = diff --git a/target/arm/cpu.h b/target/arm/cpu.h index 83a809d4bac4..666c03871fdf 100644 --- a/target/arm/cpu.h +++ b/target/arm/cpu.h @@ -932,8 +932,18 @@ struct ARMCPU { */ DECLARE_BITMAP(sve_vq_map, ARM_MAX_VQ); DECLARE_BITMAP(sve_vq_init, ARM_MAX_VQ); + + /* Generic timer counter frequency, in Hz */ + uint64_t gt_cntfrq; }; +static inline unsigned int gt_cntfrq_period_ns(ARMCPU *cpu) +{ + /* XXX: Could include qemu/timer.h to get NANOSECONDS_PER_SECOND? */ + const unsigned int ns_per_s = 1000 * 1000 * 1000; + return ns_per_s > cpu->gt_cntfrq ? ns_per_s / cpu->gt_cntfrq : 1; +} + void arm_cpu_post_init(Object *obj); uint64_t arm_cpu_mp_affinity(int idx, uint8_t clustersz); diff --git a/target/arm/helper.c b/target/arm/helper.c index 65c4441a3896..1cc0551081a0 100644 --- a/target/arm/helper.c +++ b/target/arm/helper.c @@ -2409,7 +2409,9 @@ static CPAccessResult gt_stimer_access(CPUARMState *env, static uint64_t gt_get_countervalue(CPUARMState *env) { - return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / GTIMER_SCALE; + ARMCPU *cpu = env_archcpu(env); + + return qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / gt_cntfrq_period_ns(cpu); } static void gt_recalc_timer(ARMCPU *cpu, int timeridx) @@ -2445,7 +2447,7 @@ static void gt_recalc_timer(ARMCPU *cpu, int timeridx) * set the timer for as far in the future as possible. When the * timer expires we will reset the timer for any remaining period. */ - if (nexttick > INT64_MAX / GTIMER_SCALE) { + if (nexttick > INT64_MAX / gt_cntfrq_period_ns(cpu)) { timer_mod_ns(cpu->gt_timer[timeridx], INT64_MAX); } else { timer_mod(cpu->gt_timer[timeridx], nexttick); @@ -2874,11 +2876,13 @@ static const ARMCPRegInfo generic_timer_cp_reginfo[] = { static uint64_t gt_virt_cnt_read(CPUARMState *env, const ARMCPRegInfo *ri) { + ARMCPU *cpu = env_archcpu(env); + /* 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; + return cpu_get_clock() / gt_cntfrq_period(cpu); } static const ARMCPRegInfo generic_timer_cp_reginfo[] = {
Prepare for SoCs such as the ASPEED AST2600 whose firmware configures CNTFRQ to values significantly larger than the static 62.5MHz value currently derived from GTIMER_SCALE. As the OS potentially derives its timer periods from the CNTFRQ value the lack of support for running QEMUTimers at the appropriate rate leads to sticky behaviour in the guest. Substitute the GTIMER_SCALE constant with use of a helper to derive the period from gt_cntfrq stored in struct ARMCPU. Initially set gt_cntfrq to the frequency associated with GTIMER_SCALE so current behaviour is maintained. Signed-off-by: Andrew Jeffery <andrew@aj.id.au> --- target/arm/cpu.c | 2 ++ target/arm/cpu.h | 10 ++++++++++ target/arm/helper.c | 10 +++++++--- 3 files changed, 19 insertions(+), 3 deletions(-)