honor ACPI v4 FADT flags

- force use of physical APIC mode if indicated so (as we don't support
  xAPIC cluster mode, the respective flag is taken to force physical
  mode too)
- don't use MSI if indicated so (implies no IOMMU)

Both can be overridden on the command line, for the MSI case this at
once adds a new command line option allowing to turn off PCI MSI (IOMMU
and HPET are unaffected by this).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/xen/arch/x86/hpet.c b/xen/arch/x86/hpet.c
index fb875523f0..02926b5319 100644
--- a/xen/arch/x86/hpet.c
+++ b/xen/arch/x86/hpet.c
@@ -381,6 +381,9 @@ static void __init hpet_fsb_cap_lookup(void)
     u32 id;
     unsigned int i, num_chs;
 
+    if ( unlikely(acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_MSI) )
+        return;
+
     id = hpet_read32(HPET_ID);
 
     num_chs = ((id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT);