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

Jeremy Fitzhardinge
2010-07-26T17:19:41Z

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@linux.vnet.ibm.com>
>
> ---
> 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
>