cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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hyperv_timer.h (3226B)

      1/* SPDX-License-Identifier: GPL-2.0 */
      2
      3/*
      4 * Definitions for the clocksource provided by the Hyper-V
      5 * hypervisor to guest VMs, as described in the Hyper-V Top
      6 * Level Functional Spec (TLFS).
      7 *
      8 * Copyright (C) 2019, Microsoft, Inc.
      9 *
     10 * Author:  Michael Kelley <mikelley@microsoft.com>
     11 */
     12
     13#ifndef __CLKSOURCE_HYPERV_TIMER_H
     14#define __CLKSOURCE_HYPERV_TIMER_H
     15
     16#include <linux/clocksource.h>
     17#include <linux/math64.h>
     18#include <asm/mshyperv.h>
     19
     20#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
     21#define HV_MIN_DELTA_TICKS 1
     22
     23#ifdef CONFIG_HYPERV_TIMER
     24
     25/* Routines called by the VMbus driver */
     26extern int hv_stimer_alloc(bool have_percpu_irqs);
     27extern int hv_stimer_cleanup(unsigned int cpu);
     28extern void hv_stimer_legacy_init(unsigned int cpu, int sint);
     29extern void hv_stimer_legacy_cleanup(unsigned int cpu);
     30extern void hv_stimer_global_cleanup(void);
     31extern void hv_stimer0_isr(void);
     32
     33extern void hv_init_clocksource(void);
     34
     35extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
     36
     37static inline notrace u64
     38hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc)
     39{
     40	u64 scale, offset;
     41	u32 sequence;
     42
     43	/*
     44	 * The protocol for reading Hyper-V TSC page is specified in Hypervisor
     45	 * Top-Level Functional Specification ver. 3.0 and above. To get the
     46	 * reference time we must do the following:
     47	 * - READ ReferenceTscSequence
     48	 *   A special '0' value indicates the time source is unreliable and we
     49	 *   need to use something else. The currently published specification
     50	 *   versions (up to 4.0b) contain a mistake and wrongly claim '-1'
     51	 *   instead of '0' as the special value, see commit c35b82ef0294.
     52	 * - ReferenceTime =
     53	 *        ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset
     54	 * - READ ReferenceTscSequence again. In case its value has changed
     55	 *   since our first reading we need to discard ReferenceTime and repeat
     56	 *   the whole sequence as the hypervisor was updating the page in
     57	 *   between.
     58	 */
     59	do {
     60		sequence = READ_ONCE(tsc_pg->tsc_sequence);
     61		if (!sequence)
     62			return U64_MAX;
     63		/*
     64		 * Make sure we read sequence before we read other values from
     65		 * TSC page.
     66		 */
     67		smp_rmb();
     68
     69		scale = READ_ONCE(tsc_pg->tsc_scale);
     70		offset = READ_ONCE(tsc_pg->tsc_offset);
     71		*cur_tsc = hv_get_raw_timer();
     72
     73		/*
     74		 * Make sure we read sequence after we read all other values
     75		 * from TSC page.
     76		 */
     77		smp_rmb();
     78
     79	} while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
     80
     81	return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
     82}
     83
     84static inline notrace u64
     85hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
     86{
     87	u64 cur_tsc;
     88
     89	return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
     90}
     91
     92#else /* CONFIG_HYPERV_TIMER */
     93static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
     94{
     95	return NULL;
     96}
     97
     98static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
     99				       u64 *cur_tsc)
    100{
    101	return U64_MAX;
    102}
    103
    104static inline int hv_stimer_cleanup(unsigned int cpu) { return 0; }
    105static inline void hv_stimer_legacy_init(unsigned int cpu, int sint) {}
    106static inline void hv_stimer_legacy_cleanup(unsigned int cpu) {}
    107static inline void hv_stimer_global_cleanup(void) {}
    108static inline void hv_stimer0_isr(void) {}
    109
    110#endif /* CONFIG_HYPERV_TIMER */
    111
    112#endif