x86: consistently serialize CMOS/RTC accesses on rtc_lock

Since RTC/CMOS accesses aren't atomic, there are possible races
between code paths setting the index register and subsequently
reading/writing the data register. This is supposed to be dealt with
by acquiring rtc_lock, but two places up to now lacked respective
synchronization: Accesses to the EFI time functions and
smpboot_{setup,restore}_warm_reset_vector().

This in turn requires no longer directly passing through guest writes
to the index register, but instead using a machanism similar to that
for PCI config space method 1 accesses.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index 382e2dbcb2..3e4408a0b9 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -258,6 +258,7 @@ struct arch_domain
     /* I/O-port admin-specified access capabilities. */
     struct rangeset *ioport_caps;
     uint32_t pci_cf8;
+    uint8_t cmos_idx;
 
     struct list_head pdev_list;