pvclock-abi.h 1.49 KB
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_PVCLOCK_ABI_H
#define _ASM_X86_PVCLOCK_ABI_H
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#ifndef __ASSEMBLY__

/*
 * These structs MUST NOT be changed.
 * They are the ABI between hypervisor and guest OS.
 * Both Xen and KVM are using this.
 *
 * pvclock_vcpu_time_info holds the system time and the tsc timestamp
 * of the last update. So the guest can use the tsc delta to get a
 * more precise system time.  There is one per virtual cpu.
 *
 * pvclock_wall_clock references the point in time when the system
 * time was zero (usually boot time), thus the guest calculates the
 * current wall clock by adding the system time.
 *
 * Protocol for the "version" fields is: hypervisor raises it (making
 * it uneven) before it starts updating the fields and raises it again
 * (making it even) when it is done.  Thus the guest can make sure the
 * time values it got are consistent by checking the version before
 * and after reading them.
 */

struct pvclock_vcpu_time_info {
	u32   version;
	u32   pad0;
	u64   tsc_timestamp;
	u64   system_time;
	u32   tsc_to_system_mul;
	s8    tsc_shift;
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	u8    flags;
	u8    pad[2];
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} __attribute__((__packed__)); /* 32 bytes */

struct pvclock_wall_clock {
	u32   version;
	u32   sec;
	u32   nsec;
} __attribute__((__packed__));

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#define PVCLOCK_TSC_STABLE_BIT	(1 << 0)
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#define PVCLOCK_GUEST_STOPPED	(1 << 1)
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/* PVCLOCK_COUNTS_FROM_ZERO broke ABI and can't be used anymore. */
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#define PVCLOCK_COUNTS_FROM_ZERO (1 << 2)
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_X86_PVCLOCK_ABI_H */