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0408f16b43
Microsoft Hypervisor root partition has to map the TSC page specified by the hypervisor, instead of providing the page to the hypervisor like it's done in the guest partitions. However, it's too early to map the page when the clock is initialized, so, the actual mapping is happening later. Signed-off-by: Stanislav Kinsburskiy <stanislav.kinsburskiy@gmail.com> CC: "K. Y. Srinivasan" <kys@microsoft.com> CC: Haiyang Zhang <haiyangz@microsoft.com> CC: Wei Liu <wei.liu@kernel.org> CC: Dexuan Cui <decui@microsoft.com> CC: Thomas Gleixner <tglx@linutronix.de> CC: Ingo Molnar <mingo@redhat.com> CC: Borislav Petkov <bp@alien8.de> CC: Dave Hansen <dave.hansen@linux.intel.com> CC: x86@kernel.org CC: "H. Peter Anvin" <hpa@zytor.com> CC: Daniel Lezcano <daniel.lezcano@linaro.org> CC: linux-hyperv@vger.kernel.org CC: linux-kernel@vger.kernel.org Reviewed-by: Michael Kelley <mikelley@microsoft.com> Reviewed-by: Anirudh Rayabharam <anrayabh@linux.microsoft.com> Link: https://lore.kernel.org/r/166759443644.385891.15921594265843430260.stgit@skinsburskii-cloud-desktop.internal.cloudapp.net Signed-off-by: Wei Liu <wei.liu@kernel.org>
119 lines
3.3 KiB
C
119 lines
3.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Definitions for the clocksource provided by the Hyper-V
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* hypervisor to guest VMs, as described in the Hyper-V Top
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* Level Functional Spec (TLFS).
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*
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* Copyright (C) 2019, Microsoft, Inc.
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*
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* Author: Michael Kelley <mikelley@microsoft.com>
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*/
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#ifndef __CLKSOURCE_HYPERV_TIMER_H
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#define __CLKSOURCE_HYPERV_TIMER_H
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#include <linux/clocksource.h>
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#include <linux/math64.h>
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#include <asm/mshyperv.h>
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#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
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#define HV_MIN_DELTA_TICKS 1
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#ifdef CONFIG_HYPERV_TIMER
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/* Routines called by the VMbus driver */
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extern int hv_stimer_alloc(bool have_percpu_irqs);
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extern int hv_stimer_cleanup(unsigned int cpu);
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extern void hv_stimer_legacy_init(unsigned int cpu, int sint);
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extern void hv_stimer_legacy_cleanup(unsigned int cpu);
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extern void hv_stimer_global_cleanup(void);
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extern void hv_stimer0_isr(void);
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extern void hv_init_clocksource(void);
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extern void hv_remap_tsc_clocksource(void);
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extern unsigned long hv_get_tsc_pfn(void);
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extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
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static inline notrace u64
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hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc)
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{
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u64 scale, offset;
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u32 sequence;
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/*
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* The protocol for reading Hyper-V TSC page is specified in Hypervisor
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* Top-Level Functional Specification ver. 3.0 and above. To get the
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* reference time we must do the following:
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* - READ ReferenceTscSequence
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* A special '0' value indicates the time source is unreliable and we
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* need to use something else. The currently published specification
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* versions (up to 4.0b) contain a mistake and wrongly claim '-1'
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* instead of '0' as the special value, see commit c35b82ef0294.
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* - ReferenceTime =
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* ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset
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* - READ ReferenceTscSequence again. In case its value has changed
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* since our first reading we need to discard ReferenceTime and repeat
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* the whole sequence as the hypervisor was updating the page in
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* between.
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*/
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do {
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sequence = READ_ONCE(tsc_pg->tsc_sequence);
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if (!sequence)
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return U64_MAX;
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/*
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* Make sure we read sequence before we read other values from
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* TSC page.
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*/
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smp_rmb();
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scale = READ_ONCE(tsc_pg->tsc_scale);
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offset = READ_ONCE(tsc_pg->tsc_offset);
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*cur_tsc = hv_get_raw_timer();
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/*
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* Make sure we read sequence after we read all other values
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* from TSC page.
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*/
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smp_rmb();
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} while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
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return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
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}
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static inline notrace u64
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hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
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{
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u64 cur_tsc;
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return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
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}
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#else /* CONFIG_HYPERV_TIMER */
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static inline unsigned long hv_get_tsc_pfn(void)
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{
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return 0;
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}
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static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
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{
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return NULL;
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}
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static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
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u64 *cur_tsc)
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{
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return U64_MAX;
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}
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static inline int hv_stimer_cleanup(unsigned int cpu) { return 0; }
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static inline void hv_stimer_legacy_init(unsigned int cpu, int sint) {}
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static inline void hv_stimer_legacy_cleanup(unsigned int cpu) {}
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static inline void hv_stimer_global_cleanup(void) {}
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static inline void hv_stimer0_isr(void) {}
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#endif /* CONFIG_HYPERV_TIMER */
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#endif
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