[Xen-devel] [PATCH v6 2/2] 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 access to RTC ports also needs to be trapped in order to keep
consistency, this includes RTC_PORT(0) and RTC_PORT(1) (0x70 and 0x71
respectively).

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 | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 3b9aee5..79593d9 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -49,6 +49,7 @@
 #include <xen/cpu.h>
 #include <asm/nmi.h>
 #include <asm/alternative.h>
+#include <asm/mc146818rtc.h>
 
 /* opt_nosmp: If true, secondary processors are ignored. */
 static bool_t __initdata opt_nosmp;
@@ -1535,6 +1536,16 @@ 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.
+         * Access to 1 byte RTC ports also needs to be
+         * trapped in order to keep consistency.
+         */
+        __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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