x86/xen: fix xsave capability setting
Commit 690b7f10b4f9f ("x86/xen: use capabilities instead of fake cpuid
values for xsave") introduced a regression as it tried to make use of
the fixup feature before it being available.
Fall back to the old variant testing via cpuid().
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index a732bc2..a1af4f6 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -277,26 +277,15 @@ static bool __init xen_check_mwait(void)
static bool __init xen_check_xsave(void)
{
- unsigned int err, eax, edx;
+ unsigned int cx, xsave_mask;
- /*
- * Xen 4.0 and older accidentally leaked the host XSAVE flag into guest
- * view, despite not being able to support guests using the
- * functionality. Probe for the actual availability of XSAVE by seeing
- * whether xgetbv executes successfully or raises #UD.
- */
- asm volatile("1: .byte 0x0f,0x01,0xd0\n\t" /* xgetbv */
- "xor %[err], %[err]\n"
- "2:\n\t"
- ".pushsection .fixup,\"ax\"\n\t"
- "3: movl $1,%[err]\n\t"
- "jmp 2b\n\t"
- ".popsection\n\t"
- _ASM_EXTABLE(1b, 3b)
- : [err] "=r" (err), "=a" (eax), "=d" (edx)
- : "c" (0));
+ cx = cpuid_ecx(1);
- return err == 0;
+ xsave_mask = (1 << (X86_FEATURE_XSAVE % 32)) |
+ (1 << (X86_FEATURE_OSXSAVE % 32));
+
+ /* Xen will set CR4.OSXSAVE if supported and not disabled by force */
+ return (cx & xsave_mask) == xsave_mask;
}
static void __init xen_init_capabilities(void)
@@ -317,10 +306,7 @@ static void __init xen_init_capabilities(void)
else
setup_clear_cpu_cap(X86_FEATURE_MWAIT);
- if (xen_check_xsave()) {
- setup_force_cpu_cap(X86_FEATURE_XSAVE);
- setup_force_cpu_cap(X86_FEATURE_OSXSAVE);
- } else {
+ if (!xen_check_xsave()) {
setup_clear_cpu_cap(X86_FEATURE_XSAVE);
setup_clear_cpu_cap(X86_FEATURE_OSXSAVE);
}