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.Dd February 17, 2017
.Dt X86_MSR_XCALL 9 x86
.Os
.Sh NAME
.Nm x86_msr_xcall
.Nd MSR specific cross-call
.Sh SYNOPSIS
.In x86/cpu_msr.h
.Ft void
.Fn x86_msr_xcall "void *arg1" "void *arg1"
.Sh DESCRIPTION
The
.Fn x86_msr_xcall
function provides a x86-specific IPI handler suitable for use with the
.Xr xcall 9
interface.
It can be used to ensure that a given
.Tn MSR
call is executed on all processors.
The prototype follows the
.Ft xcfunc_t
function pointer type and the opaque
.Fa arg1
pointer is casted to the following structure:
.Bd -literal -offset indent
struct msr_rw_info {
	int		msr_read;
	int		msr_type;
	uint64_t	msr_value;
	uint64_t	msr_mask;
};
.Ed
.Pp
This structure must be filled prior to the call.
Two fields are compulsory:
.Fa msr_type
is used as the address of the
.Tn MSR
and
.Fa msr_value
is the value to be written.
If
.Fa msr_read
is not zero,
.Fn x86_msr_xcall
will first read from
.Fa msr_type
and then clear the mask specified in
.Fa msr_mask
before the write operation.
.Sh EXAMPLES
The following example writes a value zero to the
.Tn MSR_THERM_CONTROL
model-specific register on all processors in the system:
.Bd -literal -offset indent
struct msr_rw_info msr;
uint64_t xc;

msr.msr_value = 0;
msr.msr_read = true;
msr.msr_type = MSR_THERM_CONTROL;
msr.msr_mask = 0x1e;

xc = xc_broadcast(0, (xcfunc_t)x86_msr_xcall, &msr, NULL);
xc_wait(xc);
.Ed
.Sh SEE ALSO
.Xr x86/rdmsr 9 ,
.Xr xcall 9