On 12/17/21 16:29, Jing Liu wrote:
+/* for KVM_CAP_XSAVE and KVM_CAP_XSAVE2 */
struct kvm_xsave {
+ /*
+ * KVM_GET_XSAVE only uses the first 4096 bytes.
+ *
+ * KVM_GET_XSAVE2 must have the size match what is returned by
+ * KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2).
+ *
+ * KVM_SET_XSAVE uses the extra field if guest_fpu::fpstate::size
+ * exceeds 4096 bytes.
KVM_GET_XSAVE2 and KVM_SET_XSAVE respectively write and read as many
bytes as are returned by KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2), when
invoked on the vm file descriptor. Currently,
KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) will only return a value that is
greater than 4096 bytes if any dynamic features have been enabled with
``arch_prctl()``; this however may change in the future.
The offsets of the state save areas in struct kvm_xsave follow the
contents of CPUID leaf 0xD on the host.
Paolo
