[PATCH] kvm: Two-way apic tpr synchronization

We report the value of cr8 to userspace on an exit.  Also let userspace change
cr8 when we re-enter the guest.  The lets 64-bit guest code maintain the tpr
correctly.

Thanks for Yaniv Kamay for the idea.

Signed-off-by: Dor Laor <dor.laor@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 5 insertions, 0 deletions

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 099f0afd394..eb3931ca680 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -1360,6 +1360,9 @@ static int kvm_dev_ioctl_run(struct kvm *kvm, struct kvm_run *kvm_run)
         if (!vcpu)
                 return -ENOENT;
 
+        /* re-sync apic's tpr */
+        vcpu->cr8 = kvm_run->cr8;
+
         if (kvm_run->emulated) {
                 kvm_arch_ops->skip_emulated_instruction(vcpu);
                 kvm_run->emulated = 0;
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 1be148f0fce..6a5f6f49e03 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -65,6 +65,8 @@ struct kvm_run {
         __u8 ready_for_interrupt_injection;
         __u8 if_flag;
         __u16 padding2;
+
+        /* in (pre_kvm_run), out (post_kvm_run) */
         __u64 cr8;
         __u64 apic_base;