Re: [PATCH RFC 2/4] Add yield hypercall for KVM guests

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 On 07/25/2010 11:14 PM, Srivatsa Vaddagiri wrote:
Add KVM hypercall for yielding vcpu timeslice.

Can you do a directed yield?

    J

Signed-off-by: Srivatsa Vaddagiri<vatsa@xxxxxxxxxxxxxxxxxx>

---
  arch/x86/include/asm/kvm_para.h |    1 +
  arch/x86/kvm/x86.c              |    7 ++++++-
  include/linux/kvm.h             |    1 +
  include/linux/kvm_para.h        |    1 +
  4 files changed, 9 insertions(+), 1 deletion(-)

Index: current/arch/x86/include/asm/kvm_para.h
===================================================================
--- current.orig/arch/x86/include/asm/kvm_para.h
+++ current/arch/x86/include/asm/kvm_para.h
@@ -16,6 +16,7 @@
  #define KVM_FEATURE_CLOCKSOURCE		0
  #define KVM_FEATURE_NOP_IO_DELAY	1
  #define KVM_FEATURE_MMU_OP		2
+#define KVM_FEATURE_YIELD		4
  /* This indicates that the new set of kvmclock msrs
   * are available. The use of 0x11 and 0x12 is deprecated
   */
Index: current/arch/x86/kvm/x86.c
===================================================================
--- current.orig/arch/x86/kvm/x86.c
+++ current/arch/x86/kvm/x86.c
@@ -1618,6 +1618,7 @@ int kvm_dev_ioctl_check_extension(long e
  	case KVM_CAP_PCI_SEGMENT:
  	case KVM_CAP_DEBUGREGS:
  	case KVM_CAP_X86_ROBUST_SINGLESTEP:
+	case KVM_CAP_YIELD_HYPERCALL:
  		r = 1;
  		break;
  	case KVM_CAP_COALESCED_MMIO:
@@ -1993,7 +1994,8 @@ static void do_cpuid_ent(struct kvm_cpui
  		entry->eax = (1<<  KVM_FEATURE_CLOCKSOURCE) |
  			     (1<<  KVM_FEATURE_NOP_IO_DELAY) |
  			     (1<<  KVM_FEATURE_CLOCKSOURCE2) |
-			     (1<<  KVM_FEATURE_CLOCKSOURCE_STABLE_BIT);
+			     (1<<  KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) |
+			     (1<<  KVM_FEATURE_YIELD);
  		entry->ebx = 0;
  		entry->ecx = 0;
  		entry->edx = 0;
@@ -4245,6 +4247,9 @@ int kvm_emulate_hypercall(struct kvm_vcp
  	case KVM_HC_MMU_OP:
  		r = kvm_pv_mmu_op(vcpu, a0, hc_gpa(vcpu, a1, a2),&ret);
  		break;
+	case KVM_HC_YIELD:
+		ret = 0;
+		yield();
  	default:
  		ret = -KVM_ENOSYS;
  		break;
Index: current/include/linux/kvm.h
===================================================================
--- current.orig/include/linux/kvm.h
+++ current/include/linux/kvm.h
@@ -524,6 +524,7 @@ struct kvm_enable_cap {
  #define KVM_CAP_PPC_OSI 52
  #define KVM_CAP_PPC_UNSET_IRQ 53
  #define KVM_CAP_ENABLE_CAP 54
+#define KVM_CAP_YIELD_HYPERCALL	55

  #ifdef KVM_CAP_IRQ_ROUTING

Index: current/include/linux/kvm_para.h
===================================================================
--- current.orig/include/linux/kvm_para.h
+++ current/include/linux/kvm_para.h
@@ -17,6 +17,7 @@

  #define KVM_HC_VAPIC_POLL_IRQ		1
  #define KVM_HC_MMU_OP			2
+#define KVM_HC_YIELD                    3

  /*
   * hypercalls use architecture specific


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