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[46.135.69.174]) by smtp.gmail.com with ESMTPSA id a2sm4996198wrg.69.2019.05.30.02.48.10 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Thu, 30 May 2019 02:48:11 -0700 (PDT) From: Vitaly Kuznetsov To: Michael Kelley Subject: Re: [PATCH v3 2/2] Drivers: hv: Move Hyper-V clocksource code to new clocksource driver In-Reply-To: <1558969089-13204-3-git-send-email-mikelley@microsoft.com> References: <1558969089-13204-1-git-send-email-mikelley@microsoft.com> <1558969089-13204-3-git-send-email-mikelley@microsoft.com> Date: Thu, 30 May 2019 11:48:10 +0200 Message-ID: <87r28gl1d1.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190530_024813_797634_F07448C6 X-CRM114-Status: GOOD ( 27.62 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "mark.rutland@arm.com" , "linux-hyperv@vger.kernel.org" , "marc.zyngier@arm.com" , "catalin.marinas@arm.com" , "jasowang@redhat.com" , "will.deacon@arm.com" , "linux-kernel@vger.kernel.org" , "marcelo.cerri@canonical.com" , "olaf@aepfle.de" , "gregkh@linuxfoundation.org" , "apw@canonical.com" , Sunil Muthuswamy , KY Srinivasan , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Michael Kelley writes: > Code for the Hyper-V specific clocksources is currently mixed > in with other Hyper-V code. Move the code to the Hyper-V specific > driver in the "clocksource" directory, while separating out > ISA dependencies so that the clocksource driver remains ISA > independent. Update the Hyper-V initialization code to call > initialization and cleanup routines since the Hyper-V synthetic > timers are not independently enumerated in ACPI. Update Hyper-V > clocksource users KVM and VDSO to get definitions from a new > include file. > > No behavior is changed and no new functionality is added. > > Suggested-by: Marc Zyngier > Signed-off-by: Michael Kelley > --- > arch/x86/entry/vdso/vclock_gettime.c | 1 + > arch/x86/entry/vdso/vma.c | 2 +- > arch/x86/hyperv/hv_init.c | 91 +----------------------- > arch/x86/include/asm/mshyperv.h | 81 +++------------------- > arch/x86/kvm/x86.c | 1 + > drivers/clocksource/hyperv_timer.c | 130 +++++++++++++++++++++++++++++++++++ > drivers/hv/hv_util.c | 1 + > include/clocksource/hyperv_timer.h | 78 +++++++++++++++++++++ > 8 files changed, 226 insertions(+), 159 deletions(-) > > diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c > index 98c7d12..7983ca2 100644 > --- a/arch/x86/entry/vdso/vclock_gettime.c > +++ b/arch/x86/entry/vdso/vclock_gettime.c > @@ -21,6 +21,7 @@ > #include > #include > #include > +#include > > #define gtod (&VVAR(vsyscall_gtod_data)) > > diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c > index babc4e7..99b38e9 100644 > --- a/arch/x86/entry/vdso/vma.c > +++ b/arch/x86/entry/vdso/vma.c > @@ -22,7 +22,7 @@ > #include > #include > #include > -#include > +#include > > #if defined(CONFIG_X86_64) > unsigned int __read_mostly vdso64_enabled = 1; > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c > index e4ba467..79f626a 100644 > --- a/arch/x86/hyperv/hv_init.c > +++ b/arch/x86/hyperv/hv_init.c > @@ -27,64 +27,13 @@ > #include > #include > #include > -#include > #include > #include > #include > - > -#ifdef CONFIG_HYPERV_TSCPAGE > - > -static struct ms_hyperv_tsc_page *tsc_pg; > - > -struct ms_hyperv_tsc_page *hv_get_tsc_page(void) > -{ > - return tsc_pg; > -} > -EXPORT_SYMBOL_GPL(hv_get_tsc_page); > - > -static u64 read_hv_clock_tsc(struct clocksource *arg) > -{ > - u64 current_tick = hv_read_tsc_page(tsc_pg); > - > - if (current_tick == U64_MAX) > - rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick); > - > - return current_tick; > -} > - > -static struct clocksource hyperv_cs_tsc = { > - .name = "hyperv_clocksource_tsc_page", > - .rating = 400, > - .read = read_hv_clock_tsc, > - .mask = CLOCKSOURCE_MASK(64), > - .flags = CLOCK_SOURCE_IS_CONTINUOUS, > -}; > -#endif > - > -static u64 read_hv_clock_msr(struct clocksource *arg) > -{ > - u64 current_tick; > - /* > - * Read the partition counter to get the current tick count. This count > - * is set to 0 when the partition is created and is incremented in > - * 100 nanosecond units. > - */ > - rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick); > - return current_tick; > -} > - > -static struct clocksource hyperv_cs_msr = { > - .name = "hyperv_clocksource_msr", > - .rating = 400, > - .read = read_hv_clock_msr, > - .mask = CLOCKSOURCE_MASK(64), > - .flags = CLOCK_SOURCE_IS_CONTINUOUS, > -}; > +#include > > void *hv_hypercall_pg; > EXPORT_SYMBOL_GPL(hv_hypercall_pg); > -struct clocksource *hyperv_cs; > -EXPORT_SYMBOL_GPL(hyperv_cs); > > u32 *hv_vp_index; > EXPORT_SYMBOL_GPL(hv_vp_index); > @@ -353,42 +302,8 @@ void __init hyperv_init(void) > > x86_init.pci.arch_init = hv_pci_init; > > - /* > - * Register Hyper-V specific clocksource. > - */ > -#ifdef CONFIG_HYPERV_TSCPAGE > - if (ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE) { > - union hv_x64_msr_hypercall_contents tsc_msr; > - > - tsc_pg = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL); > - if (!tsc_pg) > - goto register_msr_cs; > - > - hyperv_cs = &hyperv_cs_tsc; > - > - rdmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64); > - > - tsc_msr.enable = 1; > - tsc_msr.guest_physical_address = vmalloc_to_pfn(tsc_pg); > - > - wrmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64); > - > - hyperv_cs_tsc.archdata.vclock_mode = VCLOCK_HVCLOCK; > - > - clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100); > - return; > - } > -register_msr_cs: > -#endif > - /* > - * For 32 bit guests just use the MSR based mechanism for reading > - * the partition counter. > - */ > - > - hyperv_cs = &hyperv_cs_msr; > - if (ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE) > - clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100); > - > + /* Register Hyper-V specific clocksource */ > + hv_init_clocksource(); > return; > > remove_cpuhp_state: > diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h > index cc60e61..f4fa8a9 100644 > --- a/arch/x86/include/asm/mshyperv.h > +++ b/arch/x86/include/asm/mshyperv.h > @@ -105,6 +105,17 @@ static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type) > #define hv_get_crash_ctl(val) \ > rdmsrl(HV_X64_MSR_CRASH_CTL, val) > > +#define hv_get_time_ref_count(val) \ > + rdmsrl(HV_X64_MSR_TIME_REF_COUNT, val) > + > +#define hv_get_reference_tsc(val) \ > + rdmsrl(HV_X64_MSR_REFERENCE_TSC, val) > +#define hv_set_reference_tsc(val) \ > + wrmsrl(HV_X64_MSR_REFERENCE_TSC, val) > +#define hv_set_clocksource_vdso(val) \ > + ((val).archdata.vclock_mode = VCLOCK_HVCLOCK) > +#define hv_get_raw_timer() rdtsc_ordered() > + > void hyperv_callback_vector(void); > void hyperv_reenlightenment_vector(void); > #ifdef CONFIG_TRACING > @@ -133,7 +144,6 @@ static inline void hv_disable_stimer0_percpu_irq(int irq) {} > > > #if IS_ENABLED(CONFIG_HYPERV) > -extern struct clocksource *hyperv_cs; > extern void *hv_hypercall_pg; > extern void __percpu **hyperv_pcpu_input_arg; > > @@ -387,73 +397,4 @@ static inline int hyperv_flush_guest_mapping_range(u64 as, > } > #endif /* CONFIG_HYPERV */ > > -#ifdef CONFIG_HYPERV_TSCPAGE > -struct ms_hyperv_tsc_page *hv_get_tsc_page(void); > -static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, > - u64 *cur_tsc) > -{ > - u64 scale, offset; > - u32 sequence; > - > - /* > - * The protocol for reading Hyper-V TSC page is specified in Hypervisor > - * Top-Level Functional Specification ver. 3.0 and above. To get the > - * reference time we must do the following: > - * - READ ReferenceTscSequence > - * A special '0' value indicates the time source is unreliable and we > - * need to use something else. The currently published specification > - * versions (up to 4.0b) contain a mistake and wrongly claim '-1' > - * instead of '0' as the special value, see commit c35b82ef0294. > - * - ReferenceTime = > - * ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset > - * - READ ReferenceTscSequence again. In case its value has changed > - * since our first reading we need to discard ReferenceTime and repeat > - * the whole sequence as the hypervisor was updating the page in > - * between. > - */ > - do { > - sequence = READ_ONCE(tsc_pg->tsc_sequence); > - if (!sequence) > - return U64_MAX; > - /* > - * Make sure we read sequence before we read other values from > - * TSC page. > - */ > - smp_rmb(); > - > - scale = READ_ONCE(tsc_pg->tsc_scale); > - offset = READ_ONCE(tsc_pg->tsc_offset); > - *cur_tsc = rdtsc_ordered(); > - > - /* > - * Make sure we read sequence after we read all other values > - * from TSC page. > - */ > - smp_rmb(); > - > - } while (READ_ONCE(tsc_pg->tsc_sequence) != sequence); > - > - return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset; > -} > - > -static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg) > -{ > - u64 cur_tsc; > - > - return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc); > -} > - > -#else > -static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void) > -{ > - return NULL; > -} > - > -static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, > - u64 *cur_tsc) > -{ > - BUG(); > - return U64_MAX; > -} > -#endif > #endif > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 536b78c..3fbaac0 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -70,6 +70,7 @@ > #include > #include > #include > +#include > > #define CREATE_TRACE_POINTS > #include "trace.h" > diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c > index 30615f3..274614d 100644 > --- a/drivers/clocksource/hyperv_timer.c > +++ b/drivers/clocksource/hyperv_timer.c > @@ -14,6 +14,8 @@ > #include > #include > #include > +#include > +#include > #include > #include > #include > @@ -189,3 +191,131 @@ void hv_stimer_global_cleanup(void) > hv_stimer_free(); > } > EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup); > + > +/* > + * Code and definitions for the Hyper-V clocksources. Two > + * clocksources are defined: one that reads the Hyper-V defined MSR, and > + * the other that uses the TSC reference page feature as defined in the > + * TLFS. The MSR version is for compatibility with old versions of > + * Hyper-V and 32-bit x86. The TSC reference page version is preferred. > + */ > + > +struct clocksource *hyperv_cs; > +EXPORT_SYMBOL_GPL(hyperv_cs); > + > +#ifdef CONFIG_HYPERV_TSCPAGE > + > +static struct ms_hyperv_tsc_page *tsc_pg; > + > +struct ms_hyperv_tsc_page *hv_get_tsc_page(void) > +{ > + return tsc_pg; > +} > +EXPORT_SYMBOL_GPL(hv_get_tsc_page); > + > +static u64 read_hv_sched_clock_tsc(void) > +{ > + u64 current_tick = hv_read_tsc_page(tsc_pg); > + > + if (current_tick == U64_MAX) > + hv_get_time_ref_count(current_tick); > + > + return current_tick; > +} > + > +static u64 read_hv_clock_tsc(struct clocksource *arg) > +{ > + return read_hv_sched_clock_tsc(); > +} > + > +static struct clocksource hyperv_cs_tsc = { > + .name = "hyperv_clocksource_tsc_page", > + .rating = 400, > + .read = read_hv_clock_tsc, > + .mask = CLOCKSOURCE_MASK(64), > + .flags = CLOCK_SOURCE_IS_CONTINUOUS, > +}; > +#endif > + > +static u64 read_hv_sched_clock_msr(void) > +{ > + u64 current_tick; > + /* > + * Read the partition counter to get the current tick count. This count > + * is set to 0 when the partition is created and is incremented in > + * 100 nanosecond units. > + */ > + hv_get_time_ref_count(current_tick); > + return current_tick; > +} > + > +static u64 read_hv_clock_msr(struct clocksource *arg) > +{ > + return read_hv_sched_clock_msr(); > +} > + > +static struct clocksource hyperv_cs_msr = { > + .name = "hyperv_clocksource_msr", > + .rating = 400, > + .read = read_hv_clock_msr, > + .mask = CLOCKSOURCE_MASK(64), > + .flags = CLOCK_SOURCE_IS_CONTINUOUS, > +}; > + > +void __init hv_init_clocksource(void) > +{ > +#ifdef CONFIG_HYPERV_TSCPAGE > + if (ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE) { > + > + u64 tsc_msr; > + phys_addr_t phys_addr; > + > + tsc_pg = vmalloc(PAGE_SIZE); > + if (!tsc_pg) > + goto register_msr_cs; > + > + hyperv_cs = &hyperv_cs_tsc; > + phys_addr = page_to_phys(vmalloc_to_page(tsc_pg)); > + > + /* The Hyper-V TLFS specifies to preserve the value of > + * reserved bits in registers. So read the existing > + * value, preserve the low order 12 bits, and add in > + * the guest physical address (which already has at > + * least the low 12 bits set to zero since it is page > + * aligned). Also set the "enable" bit, which is bit 0. > + */ > + hv_get_reference_tsc(tsc_msr); > + tsc_msr &= GENMASK_ULL(11, 0); > + tsc_msr = tsc_msr | 0x1 | (u64)phys_addr; > + hv_set_reference_tsc(tsc_msr); > + > + hv_set_clocksource_vdso(hyperv_cs_tsc); > + clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100); > + > + /* > + * sched_clock_register is needed on ARM64 but > + * is a no-op on x86 > + */ > + sched_clock_register(read_hv_sched_clock_tsc, > + 64, HV_CLOCK_HZ); > + return; > + } > +register_msr_cs: > +#endif > + /* > + * For 32 bit guests just use the MSR based mechanism for reading > + * the partition counter. > + */ > + hyperv_cs = &hyperv_cs_msr; > + if (ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE) { > + clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100); > + > + /* > + * sched_clock_register is needed on ARM64 but > + * is a no-op on x86 > + */ > + sched_clock_register(read_hv_sched_clock_msr, > + 64, HV_CLOCK_HZ); I'm not sure about ARM, but MSR-based clocksource would be a really bad choice for sched clock on x86, this will slow things down significantly. Luckily, as you're validly stating above, sched_clock_register() is a no-op on x86 as we don't define CONFIG_GENERIC_SCHED_CLOCK. Can we actually *not* do sched_clock_register() in case TSC page is unavailable (and revert to counting jiffies or whatever)? > + } > +} > +EXPORT_SYMBOL_GPL(hv_init_clocksource); > diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c > index f10eeb1..9eff85e 100644 > --- a/drivers/hv/hv_util.c > +++ b/drivers/hv/hv_util.c > @@ -29,6 +29,7 @@ > #include > #include > #include > +#include > #include > > #include "hyperv_vmbus.h" > diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h > index ba5dc17..e17e8a2 100644 > --- a/include/clocksource/hyperv_timer.h > +++ b/include/clocksource/hyperv_timer.h > @@ -13,6 +13,10 @@ > #ifndef __CLKSOURCE_HYPERV_TIMER_H > #define __CLKSOURCE_HYPERV_TIMER_H > > +#include > +#include > +#include > + > #define HV_MAX_MAX_DELTA_TICKS 0xffffffff > #define HV_MIN_DELTA_TICKS 1 > > @@ -24,4 +28,78 @@ > extern void hv_stimer_global_cleanup(void); > extern void hv_stimer0_isr(void); > > +#if IS_ENABLED(CONFIG_HYPERV) > +extern struct clocksource *hyperv_cs; > +extern void hv_init_clocksource(void); > +#endif /* CONFIG_HYPERV */ > + > +#ifdef CONFIG_HYPERV_TSCPAGE > +extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void); > +static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, > + u64 *cur_tsc) > +{ > + u64 scale, offset; > + u32 sequence; > + > + /* > + * The protocol for reading Hyper-V TSC page is specified in Hypervisor > + * Top-Level Functional Specification ver. 3.0 and above. To get the > + * reference time we must do the following: > + * - READ ReferenceTscSequence > + * A special '0' value indicates the time source is unreliable and we > + * need to use something else. The currently published specification > + * versions (up to 4.0b) contain a mistake and wrongly claim '-1' > + * instead of '0' as the special value, see commit c35b82ef0294. > + * - ReferenceTime = > + * ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset > + * - READ ReferenceTscSequence again. In case its value has changed > + * since our first reading we need to discard ReferenceTime and repeat > + * the whole sequence as the hypervisor was updating the page in > + * between. > + */ > + do { > + sequence = READ_ONCE(tsc_pg->tsc_sequence); > + if (!sequence) > + return U64_MAX; > + /* > + * Make sure we read sequence before we read other values from > + * TSC page. > + */ > + smp_rmb(); > + > + scale = READ_ONCE(tsc_pg->tsc_scale); > + offset = READ_ONCE(tsc_pg->tsc_offset); > + *cur_tsc = hv_get_raw_timer(); > + > + /* > + * Make sure we read sequence after we read all other values > + * from TSC page. > + */ > + smp_rmb(); > + > + } while (READ_ONCE(tsc_pg->tsc_sequence) != sequence); > + > + return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset; > +} > + > +static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg) > +{ > + u64 cur_tsc; > + > + return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc); > +} > + > +#else /* CONFIG_HYPERV_TSC_PAGE */ > +static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void) > +{ > + return NULL; > +} > + > +static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, > + u64 *cur_tsc) > +{ > + return U64_MAX; > +} > +#endif /* CONFIG_HYPERV_TSCPAGE */ > + > #endif With the (theoretical) question above answered, Reviewed-by: Vitaly Kuznetsov -- Vitaly _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel