Commit afe75049 authored by Ravi Bangoria's avatar Ravi Bangoria Committed by Paul Mackerras
Browse files

KVM: PPC: Book3S HV: Allow nested guest creation when L0 hv_guest_state > L1 



On powerpc, L1 hypervisor takes help of L0 using H_ENTER_NESTED
hcall to load L2 guest state in cpu. L1 hypervisor prepares the
L2 state in struct hv_guest_state and passes a pointer to it via
hcall. Using that pointer, L0 reads/writes that state directly
from/to L1 memory. Thus L0 must be aware of hv_guest_state layout
of L1. Currently it uses version field to achieve this. i.e. If
L0 hv_guest_state.version != L1 hv_guest_state.version, L0 won't
allow nested kvm guest.

This restriction can be loosened up a bit. L0 can be taught to
understand older layout of hv_guest_state, if we restrict the
new members to be added only at the end, i.e. we can allow
nested guest even when L0 hv_guest_state.version > L1
hv_guest_state.version. Though, the other way around is not
possible.

Signed-off-by: default avatarRavi Bangoria <ravi.bangoria@linux.ibm.com>
Reviewed-by: default avatarFabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
parent 9294b8a1

arch/powerpc/include/asm/hvcall.h

+15 −2
Original line number Diff line number Diff line
@@ -535,9 +535,12 @@ struct h_cpu_char_result { 
	u64 behaviour;

};



/* Register state for entering a nested guest with H_ENTER_NESTED */

/*

 * Register state for entering a nested guest with H_ENTER_NESTED.

 * New member must be added at the end.

 */

struct hv_guest_state {

	u64 version;		/* version of this structure layout */

	u64 version;		/* version of this structure layout, must be first */

	u32 lpid;

	u32 vcpu_token;

	/* These registers are hypervisor privileged (at least for writing) */
@@ -571,6 +574,16 @@ struct hv_guest_state { 
/* Latest version of hv_guest_state structure */

#define HV_GUEST_STATE_VERSION	1



static inline int hv_guest_state_size(unsigned int version)

{

	switch (version) {

	case 1:

		return offsetofend(struct hv_guest_state, ppr);

	default:

		return -1;

	}

}



/*

 * From the document "H_GetPerformanceCounterInfo Interface" v1.07

 *

arch/powerpc/kvm/book3s_hv_nested.c

+45 −10
Original line number Diff line number Diff line
@@ -215,12 +215,51 @@ static void kvmhv_nested_mmio_needed(struct kvm_vcpu *vcpu, u64 regs_ptr) 
	}

}



static int kvmhv_read_guest_state_and_regs(struct kvm_vcpu *vcpu,

					   struct hv_guest_state *l2_hv,

					   struct pt_regs *l2_regs,

					   u64 hv_ptr, u64 regs_ptr)

{

	int size;



	if (kvm_vcpu_read_guest(vcpu, hv_ptr, &l2_hv->version,

				sizeof(l2_hv->version)))

		return -1;



	if (kvmppc_need_byteswap(vcpu))

		l2_hv->version = swab64(l2_hv->version);



	size = hv_guest_state_size(l2_hv->version);

	if (size < 0)

		return -1;



	return kvm_vcpu_read_guest(vcpu, hv_ptr, l2_hv, size) ||

		kvm_vcpu_read_guest(vcpu, regs_ptr, l2_regs,

				    sizeof(struct pt_regs));

}



static int kvmhv_write_guest_state_and_regs(struct kvm_vcpu *vcpu,

					    struct hv_guest_state *l2_hv,

					    struct pt_regs *l2_regs,

					    u64 hv_ptr, u64 regs_ptr)

{

	int size;



	size = hv_guest_state_size(l2_hv->version);

	if (size < 0)

		return -1;



	return kvm_vcpu_write_guest(vcpu, hv_ptr, l2_hv, size) ||

		kvm_vcpu_write_guest(vcpu, regs_ptr, l2_regs,

				     sizeof(struct pt_regs));

}



long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu)

{

	long int err, r;

	struct kvm_nested_guest *l2;

	struct pt_regs l2_regs, saved_l1_regs;

	struct hv_guest_state l2_hv, saved_l1_hv;

	struct hv_guest_state l2_hv = {0}, saved_l1_hv;

	struct kvmppc_vcore *vc = vcpu->arch.vcore;

	u64 hv_ptr, regs_ptr;

	u64 hdec_exp;
@@ -235,17 +274,15 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu) 
	hv_ptr = kvmppc_get_gpr(vcpu, 4);

	regs_ptr = kvmppc_get_gpr(vcpu, 5);

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

	err = kvm_vcpu_read_guest(vcpu, hv_ptr, &l2_hv,

				  sizeof(struct hv_guest_state)) ||

		kvm_vcpu_read_guest(vcpu, regs_ptr, &l2_regs,

				    sizeof(struct pt_regs));

	err = kvmhv_read_guest_state_and_regs(vcpu, &l2_hv, &l2_regs,

					      hv_ptr, regs_ptr);

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

	if (err)

		return H_PARAMETER;



	if (kvmppc_need_byteswap(vcpu))

		byteswap_hv_regs(&l2_hv);

	if (l2_hv.version != HV_GUEST_STATE_VERSION)

	if (l2_hv.version > HV_GUEST_STATE_VERSION)

		return H_P2;



	if (kvmppc_need_byteswap(vcpu))
@@ -325,10 +362,8 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu) 
		byteswap_pt_regs(&l2_regs);

	}

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

	err = kvm_vcpu_write_guest(vcpu, hv_ptr, &l2_hv,

				   sizeof(struct hv_guest_state)) ||

		kvm_vcpu_write_guest(vcpu, regs_ptr, &l2_regs,

				   sizeof(struct pt_regs));

	err = kvmhv_write_guest_state_and_regs(vcpu, &l2_hv, &l2_regs,

					       hv_ptr, regs_ptr);

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

	if (err)

		return H_AUTHORITY;