[Xen-devel] [PATCH 2/2] x86/iommu: avoid mapping the APIC configuration space for hwdom

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

Current code only prevents mapping the io-apic page into the guest
physical memory map. Expand the range to be 0xFECx_xxxx as described
in the Intel 3 Series Chipset Datasheet section 3.3.1 "APIC
Configuration Space (FEC0_0000h–FECF_FFFFh)".

AMD also lists this address range in the AMD SR5690 Databook, section
2.4.2 "Non-SB IOAPIC Support".

Requested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/drivers/passthrough/x86/iommu.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/xen/drivers/passthrough/x86/iommu.c 
b/xen/drivers/passthrough/x86/iommu.c
index 88a87cf7a4..4dabfb2391 100644
--- a/xen/drivers/passthrough/x86/iommu.c
+++ b/xen/drivers/passthrough/x86/iommu.c
@@ -195,7 +195,7 @@ static bool __hwdom_init hwdom_iommu_map(const struct 
domain *d,
                                          unsigned long max_pfn)
 {
     mfn_t mfn = _mfn(pfn);
-    unsigned int i, type;
+    unsigned int type;
 
     /*
      * Set up 1:1 mapping for dom0. Default to include only conventional RAM
@@ -229,10 +229,9 @@ static bool __hwdom_init hwdom_iommu_map(const struct 
domain *d,
     /* Check that it doesn't overlap with the Interrupt Address Range. */
     if ( pfn >= 0xfee00 && pfn <= 0xfeeff )
         return false;
-    /* ... or the IO-APIC */
-    for ( i = 0; has_vioapic(d) && i < d->arch.hvm.nr_vioapics; i++ )
-        if ( pfn == PFN_DOWN(domain_vioapic(d, i)->base_address) )
-            return false;
+    /* ... or the APIC Configuration Space. */
+    if ( pfn >= 0xfec00 && pfn <= 0xfecff )
+        return false;
     /*
      * ... or the PCIe MCFG regions.
      * TODO: runtime added MMCFG regions are not checked to make sure they
-- 
2.20.1 (Apple Git-117)


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