x86/vlapic: allow setting APIC_SPIV_FOCUS_DISABLED in x2APIC mode

Current code unconditionally prevents setting APIC_SPIV_FOCUS_DISABLED
regardless of the processor model, which is not correct according to
the specification.

This issue was discovered while trying to boot a pvshim with x2APIC
enabled.

Always allow setting APIC_SPIV_FOCUS_DISABLED: the local APIC
provided to guests is emulated by Xen, and as such doesn't depend on
the features found on the hardware processor. Note for example that
Xen offers x2APIC support to guests even when the underlying hardware
doesn't have such feature.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: d7cd999faa1edf745a7597db811956cb882a5436
master date: 2019-11-22 17:52:59 +0100

diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index b5f2c895e4455bcd2715c19c5d536b22e652e35f..871c9a46b441c46e820caac7f6d968a63a6ebff6 100644 (file)
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -974,6 +974,7 @@ int hvm_x2apic_msr_write(struct vcpu *v, unsigned int msr, uint64_t msr_content)
 
     case APIC_SPIV:
         if ( msr_content & ~(APIC_VECTOR_MASK | APIC_SPIV_APIC_ENABLED |
+                             APIC_SPIV_FOCUS_DISABLED |
                              (VLAPIC_VERSION & APIC_LVR_DIRECTED_EOI
                               ? APIC_SPIV_DIRECTED_EOI : 0)) )
             return X86EMUL_UNHANDLEABLE;