Hi Michael, On 30/05/2019 16:41, Michael Kelley wrote: > From: Vincenzo Frascino <[email protected]> On Thursday, May 30, 2019 > 7:16 AM >> >> The x86 vDSO library requires some adaptations to take advantage of the >> newly introduced generic vDSO library. >> >> Introduce the following changes: >> - Modification of vdso.c to be compliant with the common vdso datapage >> - Use of lib/vdso for gettimeofday >> >> Cc: Thomas Gleixner <[email protected]> >> Signed-off-by: Vincenzo Frascino <[email protected]> >> >> >> diff --git a/arch/x86/include/asm/mshyperv-tsc.h >> b/arch/x86/include/asm/mshyperv-tsc.h >> new file mode 100644 >> index 000000000000..99c98ccea0bf >> --- /dev/null >> +++ b/arch/x86/include/asm/mshyperv-tsc.h >> @@ -0,0 +1,76 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +#ifndef _ASM_X86_MSHYPER_TSCPAGE_H >> +#define _ASM_X86_MSHYPER_TSCPAGE_H >> + >> +#include <asm/hyperv-tlfs.h> >> + >> +#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/include/asm/mshyperv.h >> b/arch/x86/include/asm/mshyperv.h >> index cc60e617931c..db095a992f3e 100644 >> --- a/arch/x86/include/asm/mshyperv.h >> +++ b/arch/x86/include/asm/mshyperv.h >> @@ -7,6 +7,7 @@ >> #include <linux/nmi.h> >> #include <asm/io.h> >> #include <asm/hyperv-tlfs.h> >> +#include <asm/mshyperv-tsc.h> >> #include <asm/nospec-branch.h> >> >> #define VP_INVAL U32_MAX >> @@ -387,73 +388,4 @@ 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 > > Vincenzo -- these changes for Hyper-V are a subset of a larger patch set > I have that moves all of the Hyper-V clock/timer code into a separate > clocksource driver in drivers/clocksource, with an include file in > includes/clocksource. That new include file should be able to work > instead of your new mshyperv-tsc.h. It also has the benefit of being > ISA neutral, so it will work with my in-progress patch set to support > Linux on Hyper-V on ARM64. See https://lkml.org/lkml/2019/5/27/231 > for the new clocksource driver patch set. >
Thank you for pointing this out, I will rebase my changes on your patches. > Michael > -- Regards, Vincenzo
