Commit 9b486cdd authored by Bibo Mao's avatar Bibo Mao Committed by Huacai Chen
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LoongArch: KVM: Add paravirt preempt feature in hypervisor side 



Feature KVM_FEATURE_PREEMPT is added to show whether vCPU is preempted
or not. It is to help guest OS scheduling or lock checking etc. Here
add KVM_FEATURE_PREEMPT feature and use one byte as preempted flag in
the steal time structure.

Signed-off-by: default avatarBibo Mao <maobibo@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent 2faec60a

arch/loongarch/include/asm/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -165,6 +165,7 @@ enum emulation_result { 


#define LOONGARCH_PV_FEAT_UPDATED	BIT_ULL(63)

#define LOONGARCH_PV_FEAT_MASK		(BIT(KVM_FEATURE_IPI) |		\

					 BIT(KVM_FEATURE_PREEMPT) |	\

					 BIT(KVM_FEATURE_STEAL_TIME) |	\

					 BIT(KVM_FEATURE_USER_HCALL) |	\

					 BIT(KVM_FEATURE_VIRT_EXTIOI))
@@ -254,6 +255,7 @@ struct kvm_vcpu_arch { 
		u64 guest_addr;

		u64 last_steal;

		struct gfn_to_hva_cache cache;

		u8  preempted;

	} st;

};

arch/loongarch/include/asm/kvm_para.h

+3 −1
Original line number Diff line number Diff line
@@ -37,8 +37,10 @@ struct kvm_steal_time { 
	__u64 steal;

	__u32 version;

	__u32 flags;

	__u32 pad[12];

	__u8  preempted;

	__u8  pad[47];

};

#define KVM_VCPU_PREEMPTED		(1 << 0)



/*

 * Hypercall interface for KVM hypervisor

arch/loongarch/include/uapi/asm/kvm.h

+1 −0
Original line number Diff line number Diff line
@@ -105,6 +105,7 @@ struct kvm_fpu { 
#define  KVM_LOONGARCH_VM_FEAT_PV_STEALTIME	7

#define  KVM_LOONGARCH_VM_FEAT_PTW		8

#define  KVM_LOONGARCH_VM_FEAT_MSGINT		9

#define  KVM_LOONGARCH_VM_FEAT_PV_PREEMPT	10



/* Device Control API on vcpu fd */

#define KVM_LOONGARCH_VCPU_CPUCFG	0

arch/loongarch/include/uapi/asm/kvm_para.h

+1 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#define CPUCFG_KVM_FEATURE		(CPUCFG_KVM_BASE + 4)

#define  KVM_FEATURE_IPI		1

#define  KVM_FEATURE_STEAL_TIME		2

#define  KVM_FEATURE_PREEMPT		3

/* BIT 24 - 31 are features configurable by user space vmm */

#define  KVM_FEATURE_VIRT_EXTIOI	24

#define  KVM_FEATURE_USER_HCALL		25

arch/loongarch/kvm/vcpu.c

+52 −1
Original line number Diff line number Diff line
@@ -181,6 +181,11 @@ static void kvm_update_stolen_time(struct kvm_vcpu *vcpu) 
	}



	st = (struct kvm_steal_time __user *)ghc->hva;

	if (kvm_guest_has_pv_feature(vcpu, KVM_FEATURE_PREEMPT)) {

		unsafe_put_user(0, &st->preempted, out);

		vcpu->arch.st.preempted = 0;

	}



	unsafe_get_user(version, &st->version, out);

	if (version & 1)

		version += 1; /* first time write, random junk */
@@ -1795,11 +1800,57 @@ static int _kvm_vcpu_put(struct kvm_vcpu *vcpu, int cpu) 
	return 0;

}



static void kvm_vcpu_set_pv_preempted(struct kvm_vcpu *vcpu)

{

	gpa_t gpa;

	struct gfn_to_hva_cache *ghc;

	struct kvm_memslots *slots;

	struct kvm_steal_time __user *st;



	gpa = vcpu->arch.st.guest_addr;

	if (!(gpa & KVM_STEAL_PHYS_VALID))

		return;



	/* vCPU may be preempted for many times */

	if (vcpu->arch.st.preempted)

		return;



	/* This happens on process exit */

	if (unlikely(current->mm != vcpu->kvm->mm))

		return;



	gpa &= KVM_STEAL_PHYS_MASK;

	ghc = &vcpu->arch.st.cache;

	slots = kvm_memslots(vcpu->kvm);

	if (slots->generation != ghc->generation || gpa != ghc->gpa) {

		if (kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc, gpa, sizeof(*st))) {

			ghc->gpa = INVALID_GPA;

			return;

		}

	}



	st = (struct kvm_steal_time __user *)ghc->hva;

	unsafe_put_user(KVM_VCPU_PREEMPTED, &st->preempted, out);

	vcpu->arch.st.preempted = KVM_VCPU_PREEMPTED;

out:

	mark_page_dirty_in_slot(vcpu->kvm, ghc->memslot, gpa_to_gfn(ghc->gpa));

}



void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)

{

	int cpu;

	int cpu, idx;

	unsigned long flags;



	if (vcpu->preempted && kvm_guest_has_pv_feature(vcpu, KVM_FEATURE_PREEMPT)) {

		/*

		 * Take the srcu lock as memslots will be accessed to check

		 * the gfn cache generation against the memslots generation.

		 */

		idx = srcu_read_lock(&vcpu->kvm->srcu);

		kvm_vcpu_set_pv_preempted(vcpu);

		srcu_read_unlock(&vcpu->kvm->srcu, idx);

	}



	local_irq_save(flags);

	cpu = smp_processor_id();

	vcpu->arch.last_sched_cpu = cpu;