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Commit 424c32f1 authored by Glauber Costa's avatar Glauber Costa Committed by Avi Kivity
Browse files

x86, paravirt: Enable pvclock flags in vcpu_time_info structure 



This patch removes one padding byte and transform it into a flags
field. New versions of guests using pvclock will query these flags
upon each read.

Flags, however, will only be interpreted when the guest decides to.
It uses the pvclock_valid_flags function to signal that a specific
set of flags should be taken into consideration. Which flags are valid
are usually devised via HV negotiation.

Signed-off-by: default avatarGlauber Costa <glommer@redhat.com>
CC: Jeremy Fitzhardinge <jeremy@goop.org>
Acked-by: default avatarZachary Amsden <zamsden@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent b69e8cae

arch/x86/include/asm/pvclock-abi.h

+2 −1
Original line number Diff line number Diff line
@@ -29,7 +29,8 @@ struct pvclock_vcpu_time_info { 
	u64   system_time;

	u32   tsc_to_system_mul;

	s8    tsc_shift;

	u8    pad[3];

	u8    flags;

	u8    pad[2];

} __attribute__((__packed__)); /* 32 bytes */



struct pvclock_wall_clock {

arch/x86/include/asm/pvclock.h

+1 −0
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 


/* some helper functions for xen and kvm pv clock sources */

cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);

void pvclock_set_flags(u8 flags);

unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src);

void pvclock_read_wallclock(struct pvclock_wall_clock *wall,

			    struct pvclock_vcpu_time_info *vcpu,

arch/x86/kernel/pvclock.c

+9 −0
Original line number Diff line number Diff line
@@ -31,8 +31,16 @@ struct pvclock_shadow_time { 
	u32 tsc_to_nsec_mul;

	int tsc_shift;

	u32 version;

	u8  flags;

};



static u8 valid_flags __read_mostly = 0;



void pvclock_set_flags(u8 flags)

{

	valid_flags = flags;

}



/*

 * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,

 * yielding a 64-bit result.
@@ -91,6 +99,7 @@ static unsigned pvclock_get_time_values(struct pvclock_shadow_time *dst, 
		dst->system_timestamp  = src->system_time;

		dst->tsc_to_nsec_mul   = src->tsc_to_system_mul;

		dst->tsc_shift         = src->tsc_shift;

		dst->flags             = src->flags;

		rmb();		/* test version after fetching data */

	} while ((src->version & 1) || (dst->version != src->version));