From: Andrew Cooper Date: Mon, 12 Sep 2016 09:30:00 +0000 (+0100) Subject: x86/domctl: Simplfy XEN_DOMCTL_getvcpuextstate when xsave is not in use X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~407 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=6accc5f1af1b51ea4fefcddce72db4e795f580c3;p=xen.git x86/domctl: Simplfy XEN_DOMCTL_getvcpuextstate when xsave is not in use Older guests will not use xsave even if it is available. As such, their xcr0_accum will be 0 at the point of migrate. If it is empty, forgo the memory allocation and serialisation into a zero-length buffer. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich --- diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c index 815bd334a3..5aa9f3aef0 100644 --- a/xen/arch/x86/domctl.c +++ b/xen/arch/x86/domctl.c @@ -1087,11 +1087,13 @@ long arch_do_domctl( ret = -EFAULT; offset += sizeof(v->arch.xcr0_accum); - if ( !ret ) + + /* Serialise xsave state, if there is any. */ + if ( !ret && size > PV_XSAVE_HDR_SIZE ) { - void *xsave_area; + unsigned int xsave_size = size - PV_XSAVE_HDR_SIZE; + void *xsave_area = xmalloc_bytes(xsave_size); - xsave_area = xmalloc_bytes(size); if ( !xsave_area ) { ret = -ENOMEM; @@ -1099,11 +1101,10 @@ long arch_do_domctl( goto vcpuextstate_out; } - expand_xsave_states(v, xsave_area, - size - PV_XSAVE_HDR_SIZE); + expand_xsave_states(v, xsave_area, xsave_size); if ( copy_to_guest_offset(evc->buffer, offset, xsave_area, - size - PV_XSAVE_HDR_SIZE) ) + xsave_size) ) ret = -EFAULT; xfree(xsave_area); }