31 lines
755 B
Go
31 lines
755 B
Go
|
package amd64util
|
||
|
|
|
||
|
|
import (
|
||
|
|
"sync"
|
||
|
|
)
|
||
|
|
|
||
|
|
var xstateMaxSize int
|
||
|
|
var loadXstateMaxSizeOnce sync.Once
|
||
|
|
|
||
|
|
func cpuid(axIn, cxIn uint32) (axOut, bxOut, cxOut, dxOut uint32)
|
||
|
|
|
||
|
|
func AMD64XstateMaxSize() int {
|
||
|
|
loadXstateMaxSizeOnce.Do(func() {
|
||
|
|
// See Intel 64 and IA-32 Architecture Software Developer's Manual, Vol. 1
|
||
|
|
// chapter 13.2 and Vol. 2A CPUID instruction for a description of all the
|
||
|
|
// magic constants.
|
||
|
|
|
||
|
|
_, _, cx, _ := cpuid(0x01, 0x00)
|
||
|
|
|
||
|
|
if cx&(1<<26) == 0 { // Vol. 2A, Table 3-10, XSAVE enabled bit check
|
||
|
|
// XSAVE not supported by this processor
|
||
|
|
xstateMaxSize = _XSTATE_MAX_KNOWN_SIZE
|
||
|
|
return
|
||
|
|
}
|
||
|
|
|
||
|
|
_, _, cx, _ = cpuid(0x0d, 0x00) // processor extended state enumeration main leaf
|
||
|
|
xstateMaxSize = int(cx)
|
||
|
|
})
|
||
|
|
return xstateMaxSize
|
||
|
|
}
|