Il 14/03/2014 13:47, James Hogan ha scritto:
From: Sanjay Lal <sanj...@kymasys.com>
Compare/Count timer interrupts are handled in-kernel for KVM, so don't
bother starting it in QEMU.
Signed-off-by: Sanjay Lal <sanj...@kymasys.com>
Signed-off-by: James Hogan <james.ho...@imgtec.com>
Reviewed-by: Aurelien Jarno <aurel...@aurel32.net>
---
Changes in v2:
- Expand commit message
- Rebase on v1.7.0
- Wrap comment
---
hw/mips/cputimer.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/hw/mips/cputimer.c b/hw/mips/cputimer.c
index c8b4b00..52570fd 100644
--- a/hw/mips/cputimer.c
+++ b/hw/mips/cputimer.c
@@ -23,6 +23,7 @@
#include "hw/hw.h"
#include "hw/mips/cpudevs.h"
#include "qemu/timer.h"
+#include "sysemu/kvm.h"
#define TIMER_FREQ 100 * 1000 * 1000
@@ -141,7 +142,13 @@ static void mips_timer_cb (void *opaque)
void cpu_mips_clock_init (CPUMIPSState *env)
{
- env->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, &mips_timer_cb, env);
- env->CP0_Compare = 0;
- cpu_mips_store_count(env, 1);
+ /*
+ * If we're in KVM mode, don't start the periodic timer, that is handled in
+ * kernel.
+ */
+ if (!kvm_enabled()) {
+ env->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, &mips_timer_cb, env);
+ env->CP0_Compare = 0;
+ cpu_mips_store_count(env, 1);
+ }
}
I hate to make you do unrelated changes, but... initializing CP0_Compare
is unnecessary, it should already be 0; and for CP0_Count it should not
be done here. but in cpu_state_reset function. Then here you can call
qemu_register_reset to register another reset callback, and call
cpu_mips_timer_update in that callback.
I'm asking because while
if (!kvm_enabled()) {
env->timer = ...
qemu_register_reset(...);
}
is fine, changing values of registers conditionally is not.
Also, I noticed two things in the implementation of the CPU timer that
should be fixed:
1) right now the hypervisor's frequency is hardcoded to 1/4th of the
host, while QEMU's is 100 MHz. It would be nice to make them either
consistent, or customizable (you can use another ONE_REG interface to
set CPU parameters).
2) in KVM, CP0_Count does not start at the same value on guest reset.
There is a comment that "Linux doesn't seem to write into COUNT", but
QEMU does. So KVM should implement CP0_Count writes and adjust the
"bias" of the guest CP0_Count.
In fact, right now kvm_mips_te_put_cp0_registers should always return
-EINVAL because KVM_REG_MIPS_CP0_COUNT is not handled in
kvm_mips_get/set_reg. Am I missing something?
Paolo
