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x86/xen: fix xsave capability setting

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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>
This commit is contained in:
Juergen Gross 2017-04-25 08:47:40 +02:00
parent 3dbd8204af
commit 40f4ac0b51
1 changed files with 8 additions and 22 deletions
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30
arch/x86/xen/enlighten_pv.c
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@ -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);
}