[Xen-devel] [PATCH RFC V11 18/18] kvm hypervisor: Add directed yield in vcpu block path

[Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>]

kvm hypervisor: Add directed yield in vcpu block path

From: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>

We use the improved PLE handler logic in vcpu block patch for
scheduling rather than plain schedule, so that we can make
intelligent decisions.

Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
---
 Changes: 
 Added stubs for missing architecture (Gleb)

 arch/arm/include/asm/kvm_host.h     |    5 +++++
 arch/arm64/include/asm/kvm_host.h   |    5 +++++
 arch/ia64/include/asm/kvm_host.h    |    5 +++++
 arch/mips/include/asm/kvm_host.h    |    5 +++++
 arch/powerpc/include/asm/kvm_host.h |    5 +++++
 arch/s390/include/asm/kvm_host.h    |    5 +++++
 arch/x86/include/asm/kvm_host.h     |    2 +-
 arch/x86/kvm/x86.c                  |    8 ++++++++
 include/linux/kvm_host.h            |    2 +-
 virt/kvm/kvm_main.c                 |    6 ++++--
 10 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 7d22517..94836c0 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -226,6 +226,11 @@ static inline int kvm_arch_dev_ioctl_check_extension(long 
ext)
        return 0;
 }
 
+static inline void kvm_do_schedule(struct kvm_vcpu *vcpu)
+{
+       schedule();
+}
+
 int kvm_perf_init(void);
 int kvm_perf_teardown(void);
 
diff --git a/arch/arm64/include/asm/kvm_host.h 
b/arch/arm64/include/asm/kvm_host.h
index 644d739..cd18913 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -186,6 +186,11 @@ int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
 int kvm_perf_init(void);
 int kvm_perf_teardown(void);
 
+static inline void kvm_do_schedule(struct kvm_vcpu *vcpu)
+{
+       schedule();
+}
+
 static inline void __cpu_init_hyp_mode(phys_addr_t boot_pgd_ptr,
                                       phys_addr_t pgd_ptr,
                                       unsigned long hyp_stack_ptr,
diff --git a/arch/ia64/include/asm/kvm_host.h b/arch/ia64/include/asm/kvm_host.h
index 989dd3f..999ab15 100644
--- a/arch/ia64/include/asm/kvm_host.h
+++ b/arch/ia64/include/asm/kvm_host.h
@@ -595,6 +595,11 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu);
 int kvm_pal_emul(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run);
 void kvm_sal_emul(struct kvm_vcpu *vcpu);
 
+static inline void kvm_do_schedule(struct kvm_vcpu *vcpu)
+{
+       schedule();
+}
+
 #define __KVM_HAVE_ARCH_VM_ALLOC 1
 struct kvm *kvm_arch_alloc_vm(void);
 void kvm_arch_free_vm(struct kvm *kvm);
diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index 4d6fa0b..2c4aae9 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -655,6 +655,11 @@ extern int kvm_mips_trans_mtc0(uint32_t inst, uint32_t 
*opc,
                               struct kvm_vcpu *vcpu);
 
 /* Misc */
+static inline void kvm_do_schedule(struct kvm_vcpu *vcpu)
+{
+       schedule();
+}
+
 extern void mips32_SyncICache(unsigned long addr, unsigned long size);
 extern int kvm_mips_dump_stats(struct kvm_vcpu *vcpu);
 extern unsigned long kvm_mips_get_ramsize(struct kvm *kvm);
diff --git a/arch/powerpc/include/asm/kvm_host.h 
b/arch/powerpc/include/asm/kvm_host.h
index af326cd..1aeecc0 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -628,4 +628,9 @@ struct kvm_vcpu_arch {
 #define __KVM_HAVE_ARCH_WQP
 #define __KVM_HAVE_CREATE_DEVICE
 
+static inline void kvm_do_schedule(struct kvm_vcpu *vcpu)
+{
+       schedule();
+}
+
 #endif /* __POWERPC_KVM_HOST_H__ */
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 3238d40..d3409fa 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -274,6 +274,11 @@ struct kvm_arch{
        int css_support;
 };
 
+static inline void kvm_do_schedule(struct kvm_vcpu *vcpu)
+{
+       schedule();
+}
+
 extern int sie64a(struct kvm_s390_sie_block *, u64 *);
 extern char sie_exit;
 #endif
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1d1f711..ed06ecd 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1053,5 +1053,5 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct 
msr_data *msr_info);
 int kvm_pmu_read_pmc(struct kvm_vcpu *vcpu, unsigned pmc, u64 *data);
 void kvm_handle_pmu_event(struct kvm_vcpu *vcpu);
 void kvm_deliver_pmi(struct kvm_vcpu *vcpu);
-
+void kvm_do_schedule(struct kvm_vcpu *vcpu);
 #endif /* _ASM_X86_KVM_HOST_H */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 640d112..ea64481 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7319,6 +7319,14 @@ bool kvm_arch_can_inject_async_page_present(struct 
kvm_vcpu *vcpu)
                        kvm_x86_ops->interrupt_allowed(vcpu);
 }
 
+void kvm_do_schedule(struct kvm_vcpu *vcpu)
+{
+       /* We try to yield to a kicked vcpu else do a schedule */
+       if (kvm_vcpu_on_spin(vcpu) <= 0)
+               schedule();
+}
+EXPORT_SYMBOL_GPL(kvm_do_schedule);
+
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_page_fault);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a63d83e..fab21ec 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -568,7 +568,7 @@ void mark_page_dirty_in_slot(struct kvm *kvm, struct 
kvm_memory_slot *memslot,
 void kvm_vcpu_block(struct kvm_vcpu *vcpu);
 void kvm_vcpu_kick(struct kvm_vcpu *vcpu);
 bool kvm_vcpu_yield_to(struct kvm_vcpu *target);
-void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);
+bool kvm_vcpu_on_spin(struct kvm_vcpu *vcpu);
 void kvm_resched(struct kvm_vcpu *vcpu);
 void kvm_load_guest_fpu(struct kvm_vcpu *vcpu);
 void kvm_put_guest_fpu(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 1580dd4..72c49f3 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1685,7 +1685,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
                if (signal_pending(current))
                        break;
 
-               schedule();
+               kvm_do_schedule(vcpu);
        }
 
        finish_wait(&vcpu->wq, &wait);
@@ -1786,7 +1786,7 @@ bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu 
*vcpu)
 }
 #endif
 
-void kvm_vcpu_on_spin(struct kvm_vcpu *me)
+bool kvm_vcpu_on_spin(struct kvm_vcpu *me)
 {
        struct kvm *kvm = me->kvm;
        struct kvm_vcpu *vcpu;
@@ -1835,6 +1835,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
 
        /* Ensure vcpu is not eligible during next spinloop */
        kvm_vcpu_set_dy_eligible(me, false);
+
+       return yielded;
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_on_spin);
 


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