[Xen-devel] [PATCH 23 of 38] xen-dom0: only selectively disable cpu features

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Dom0 kernels actually want most of the CPU features to be enabled.
Some, like MCA/MCE, are still handled by Xen itself.

We leave APIC enabled even though we don't really have a functional
local apic so that the ACPI code will parse the corresponding tables
properly.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/xen/enlighten.c |   21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -205,18 +205,23 @@
 static void xen_cpuid(unsigned int *ax, unsigned int *bx,
                      unsigned int *cx, unsigned int *dx)
 {
-       unsigned maskedx = ~0;
+       unsigned maskedx = 0;
 
        /*
         * Mask out inconvenient features, to try and disable as many
         * unsupported kernel subsystems as possible.
         */
-       if (*ax == 1)
-               maskedx = ~((1 << X86_FEATURE_APIC) |  /* disable APIC */
-                           (1 << X86_FEATURE_ACPI) |  /* disable ACPI */
-                           (1 << X86_FEATURE_MCE)  |  /* disable MCE */
-                           (1 << X86_FEATURE_MCA)  |  /* disable MCA */
-                           (1 << X86_FEATURE_ACC));   /* thermal monitoring */
+       if (*ax == 1) {
+               maskedx =
+                       (1 << X86_FEATURE_MCE)  |  /* disable MCE */
+                       (1 << X86_FEATURE_MCA)  |  /* disable MCA */
+                       (1 << X86_FEATURE_ACC);   /* thermal monitoring */
+
+               if (!xen_initial_domain())
+                       maskedx |=
+                               (1 << X86_FEATURE_APIC) |  /* disable local 
APIC */
+                               (1 << X86_FEATURE_ACPI);  /* disable ACPI */
+       }
 
        asm(XEN_EMULATE_PREFIX "cpuid"
                : "=a" (*ax),
@@ -224,7 +229,7 @@
                  "=c" (*cx),
                  "=d" (*dx)
                : "0" (*ax), "2" (*cx));
-       *dx &= maskedx;
+       *dx &= ~maskedx;
 }
 
 static void xen_set_debugreg(int reg, unsigned long val)



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