[Qemu-devel] [PATCH] target-arm: Implement vCPU reset via KVM_ARM_VCPU_INIT for 32-bit CPUs

[Peter Maydell <peter.maydell@linaro.org>]

Implement kvm_arm_vcpu_init() as a simple call to arm_arm_vcpu_init()
(which uses the KVM_ARM_VCPU_INIT vcpu ioctl to tell the kernel
to re-initialize the vCPU), rather than via the complicated code
which saves a copy of the register state on first init and then
writes it back to the kernel. This is much simpler and brings the
32-bit KVM code into line with the 64-bit code.


Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
The kernel has always supported being able to call VCPU_INIT
multiple times for this reset effect; I just didn't realize it
was possible when I wrote the original reset code.

When kvm64.c grows support for system registers we can probably
coalesce the two kvm_arm_reset_cpu() functions into one.

I also have a vague recollection that somebody reported that
we had an actual bug in this area that this patch would fix;
however I can't now find that in the mailing list archives :-(

Testing appreciated: my ARMv7 box is being a bit flaky at the
moment; I don't *think* the occasional weird stuff I see is
the effect of this patch but it's hard to be certain.

---
 target-arm/cpu-qom.h |  4 ----
 target-arm/kvm32.c   | 19 +++++--------------
 2 files changed, 5 insertions(+), 18 deletions(-)

diff --git a/target-arm/cpu-qom.h b/target-arm/cpu-qom.h
index eaee944..ee4fbb1 100644
--- a/target-arm/cpu-qom.h
+++ b/target-arm/cpu-qom.h
@@ -72,10 +72,6 @@ typedef struct ARMCPU {
     uint64_t *cpreg_indexes;
     /* Values of the registers (cpreg_indexes[i]'s value is cpreg_values[i]) */
     uint64_t *cpreg_values;
-    /* When using KVM, keeps a copy of the initial state of the VCPU,
-     * so that on reset we can feed the reset values back into the kernel.
-     */
-    uint64_t *cpreg_reset_values;
     /* Length of the indexes, values, reset_values arrays */
     int32_t cpreg_array_len;
     /* These are used only for migration: incoming data arrives in
diff --git a/target-arm/kvm32.c b/target-arm/kvm32.c
index 068af7d..5ec4eb1 100644
--- a/target-arm/kvm32.c
+++ b/target-arm/kvm32.c
@@ -270,13 +270,6 @@ int kvm_arch_init_vcpu(CPUState *cs)
         goto out;
     }
 
-    /* Save a copy of the initial register values so that we can
-     * feed it back to the kernel on VCPU reset.
-     */
-    cpu->cpreg_reset_values = g_memdup(cpu->cpreg_values,
-                                       cpu->cpreg_array_len *
-                                       sizeof(cpu->cpreg_values[0]));
-
 out:
     g_free(rlp);
     return ret;
@@ -518,11 +511,9 @@ int kvm_arch_get_registers(CPUState *cs)
 
 void kvm_arm_reset_vcpu(ARMCPU *cpu)
 {
-    /* Feed the kernel back its initial register state */
-    memmove(cpu->cpreg_values, cpu->cpreg_reset_values,
-            cpu->cpreg_array_len * sizeof(cpu->cpreg_values[0]));
-
-    if (!write_list_to_kvmstate(cpu)) {
-        abort();
-    }
+    /* Re-init VCPU so that all registers are set to
+     * their respective reset values.
+     */
+    kvm_arm_vcpu_init(CPU(cpu));
+    write_kvmstate_to_list(cpu);
 }
-- 
1.9.2