[PATCH v4 1/2] x86/hvm: make X86_EMU_USE_PIRQ optional

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Allow selecting X86_EMU_USE_PIRQ for HVM guests, so it's no longer mandated to
be always on.

There's no restriction in Xen that forces such feature to be always on for HVM
guests, as for example PVH guests don't support it, as such allow toolstack to
select whether to enabled it on a per-domain basis.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v3:
 - Split hypervisor side from previous patch.
---
 xen/arch/x86/domain.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 8a31d18f6967..bda853e3c92b 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -725,7 +725,9 @@ static bool emulation_flags_ok(const struct domain *d, 
uint32_t emflags)
              emflags != (X86_EMU_VPCI | X86_EMU_LAPIC | X86_EMU_IOAPIC) )
             return false;
         if ( !is_hardware_domain(d) &&
-             emflags != (X86_EMU_ALL & ~X86_EMU_VPCI) &&
+             /* HVM PIRQ feature is user-selectable. */
+             (emflags & ~X86_EMU_USE_PIRQ) !=
+             (X86_EMU_ALL & ~(X86_EMU_VPCI | X86_EMU_USE_PIRQ)) &&
              emflags != X86_EMU_LAPIC )
             return false;
     }
-- 
2.43.0