[Xen-devel] [PATCH v3] xen/pvh: trap access to sensitive IO ports

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

This is needed so Xen can properly trap 4 byte accesses to 0xcf8 in order to
keep consistency with accesses to 0xcfc. The same treatment is needed for
RTC ports.

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
Changes since v2:
 - Trap RTC ports.

Changes since v1:
 - Only trap on accesses to 0xcf8.
---
 xen/arch/x86/setup.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 3b9aee5..9f19545 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1535,6 +1535,15 @@ void __hwdom_init setup_io_bitmap(struct domain *d)
         rc = rangeset_report_ranges(d->arch.ioport_caps, 0, 0x10000,
                                     io_bitmap_cb, d);
         BUG_ON(rc);
+        /*
+         * NB: we need to trap accesses to 0xcf8 in order
+         * to intercept 4 byte accesses, that need to be
+         * handled by Xen in order to keep consistency.
+         * The same applies to RTC ports.
+         */
+        __set_bit(0xcf8, d->arch.hvm_domain.io_bitmap);
+        __set_bit(RTC_PORT(0), d->arch.hvm_domain.io_bitmap);
+        __set_bit(RTC_PORT(1), d->arch.hvm_domain.io_bitmap);
     }
 }
 
-- 
1.9.5 (Apple Git-50.3)


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