This bug occurs when the SET flag of Register B is enabled. When an RTC
data register (i.e. any of the ten time/calender CMOS bytes) is set, the
data is (as expected) correctly stored in the cmos_data array. However,
since the SET flag is enabled, the function rtc_set_time is not invoked.
As a result, the field base_rtc in RTCState remains uninitialized. This
causes a problem on subsequent writes which can end up overwriting data.
To see this, consider writing data to Register A after having written
data to any of the RTC data registers; the following figure illustrates
the call stack for the Register A write operation:
+- cmos_io_port_write
+-- check_update_timer
+---- get_next_alarm
+------ rtc_update_time
In rtc_update_time, get_guest_rtc calculates the wrong time and
overwrites the previously written RTC data register values.
Signed-off-by: Alex Horn <alex.horn@cs.ox.ac.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Implement the century byte in the RTC emulation, and test that it works.
This leads to some annoying compatibility code because we need to treat
a value of 2000 for the base_year property as "use the century byte
properly" (which would be a value of 0).
The century byte will now be always-zero, rather than always-20,
for the MIPS Magnum machine whose base_year is 1980. Commit 42fc73a
(Support epoch of 1980 in RTC emulation for MIPS Magnum, 2009-01-24)
correctly said:
With an epoch of 1980 and a year of 2009, one could argue that [the
century byte] should hold either 0, 1, 19 or 20. NT 3.50 on MIPS
does not read the century byte.
so I picked the simplest and most sensible implementation which is to
return 0 for 1980-2079, 1 for 2080-2179 and so on.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
When setting a date in 1980, Linux is actually disregarding the century
byte and setting the year to 2080. This causes a year-2038 overflow
in mktimegm. Fix this by doing the days-to-seconds computation in
64-bit math.
Reported-by: Lucas Meneghel Rodrigues <lookkas@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Avoid this warning on OpenBSD:
CC tests/rtc-test.o
/src/qemu/tests/rtc-test.c: In function 'check_time':
/src/qemu/tests/rtc-test.c:171: warning: format '%ld' expects type 'long int', but argument 2 has type 'time_t'
/src/qemu/tests/rtc-test.c:173: warning: format '%ld' expects type 'long int', but argument 2 has type 'time_t'
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
