From: Jan Beulich Date: Tue, 11 Oct 2022 12:59:26 +0000 (+0200) Subject: x86/CPUID: surface suitable value in EBX of XSTATE subleaf 1 X-Git-Tag: archive/raspbian/4.16.2+90-g0d39a6d1ae-1+rpi1^2~28^2~72 X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/%22/%22http:/www.example.com/cgi/%22?a=commitdiff_plain;h=e8882bcfe35520e950ba60acd6e67e65f1ce90a8;p=xen.git x86/CPUID: surface suitable value in EBX of XSTATE subleaf 1 While the SDM isn't very clear about this, our present behavior make Linux 5.19 unhappy. As of commit 8ad7e8f69695 ("x86/fpu/xsave: Support XSAVEC in the kernel") they're using this CPUID output also to size the compacted area used by XSAVEC. Getting back zero there isn't really liked, yet for PV that's the default on capable hardware: XSAVES isn't exposed to PV domains. Considering that the size reported is that of the compacted save area, I view Linux'es assumption as appropriate (short of the SDM properly considering the case). Therefore we need to populate the field also when only XSAVEC is supported for a guest. Fixes: 460b9a4b3630 ("x86/xsaves: enable xsaves/xrstors for hvm guest") Fixes: 8d050ed1097c ("x86: don't expose XSAVES capability to PV guests") Signed-off-by: Jan Beulich Acked-by: Andrew Cooper master commit: c3bd0b83ea5b7c0da6542687436042eeea1e7909 master date: 2022-08-24 14:23:59 +0200 --- diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c index ff335f1639..a647331f47 100644 --- a/xen/arch/x86/cpuid.c +++ b/xen/arch/x86/cpuid.c @@ -1060,7 +1060,7 @@ void guest_cpuid(const struct vcpu *v, uint32_t leaf, switch ( subleaf ) { case 1: - if ( p->xstate.xsaves ) + if ( p->xstate.xsavec || p->xstate.xsaves ) { /* * TODO: Figure out what to do for XSS state. VT-x manages