[Xen-devel] [PATCH] x86: don't expose SYSENTER on unknown CPUs

["Jan Beulich" <JBeulich@xxxxxxxx>]

So far we only ever set up the respective MSRs on Intel CPUs, yet we
hide the feature only on a 32-bit hypervisor. That prevents booting of
PV guests on top of a 64-bit hypervisor making use of the instruction
on unknown CPUs (VIA in this case).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -55,6 +55,7 @@ static void default_init(struct cpuinfo_
        /* Not much we can do here... */
        /* Check if at least it has cpuid */
        BUG_ON(c->cpuid_level == -1);
+       __clear_bit(X86_FEATURE_SEP, c->x86_capability);
 }
 
 static struct cpu_dev default_cpu = {

Attachment: x86_64-prevent-sysenter.patch
Description: Text document

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