KVM: PPC: Introduce shared page

For transparent variable sharing between the hypervisor and guest, I introduce
a shared page. This shared page will contain all the registers the guest can
read and write safely without exiting guest context.

This patch only implements the stubs required for the basic structure of the
shared page. The actual register moving follows.

Signed-off-by: Alexander Graf <[e-mail]>
Signed-off-by: Avi Kivity <[e-mail]>

arch/powerpc/include/asm/kvm_host.h

···
 #include <linux/interrupt.h>
 #include <linux/types.h>
 #include <linux/kvm_types.h>
+#include <linux/kvm_para.h>
 #include <asm/kvm_asm.h>
 
 #define KVM_MAX_VCPUS 1
···
 	struct tasklet_struct tasklet;
 	u64 dec_jiffies;
 	unsigned long pending_exceptions;
+	struct kvm_vcpu_arch_shared *shared;
 
 #ifdef CONFIG_PPC_BOOK3S
 	struct hlist_head hpte_hash_pte[HPTEG_HASH_NUM_PTE];

arch/powerpc/include/asm/kvm_para.h

···
 #ifndef __POWERPC_KVM_PARA_H__
 #define __POWERPC_KVM_PARA_H__
 
+#include <linux/types.h>
+
+struct kvm_vcpu_arch_shared {
+};
+
 #ifdef __KERNEL__
 
 static inline int kvm_para_available(void)

arch/powerpc/kernel/asm-offsets.c

···
 	DEFINE(VCPU_SPRG6, offsetof(struct kvm_vcpu, arch.sprg6));
 	DEFINE(VCPU_SPRG7, offsetof(struct kvm_vcpu, arch.sprg7));
 	DEFINE(VCPU_SHADOW_PID, offsetof(struct kvm_vcpu, arch.shadow_pid));
+	DEFINE(VCPU_SHARED, offsetof(struct kvm_vcpu, arch.shared));
 
 	/* book3s */
 #ifdef CONFIG_PPC_BOOK3S

arch/powerpc/kvm/44x.c

···
 	if (err)
 		goto free_vcpu;
 
+	vcpu->arch.shared = (void*)__get_free_page(GFP_KERNEL|__GFP_ZERO);
+	if (!vcpu->arch.shared)
+		goto uninit_vcpu;
+
 	return vcpu;
 
+uninit_vcpu:
+	kvm_vcpu_uninit(vcpu);
 free_vcpu:
 	kmem_cache_free(kvm_vcpu_cache, vcpu_44x);
 out:
···
 {
 	struct kvmppc_vcpu_44x *vcpu_44x = to_44x(vcpu);
 
+	free_page((unsigned long)vcpu->arch.shared);
 	kvm_vcpu_uninit(vcpu);
 	kmem_cache_free(kvm_vcpu_cache, vcpu_44x);
 }

arch/powerpc/kvm/book3s.c

···
 	if (err)
 		goto free_shadow_vcpu;
 
+	vcpu->arch.shared = (void*)__get_free_page(GFP_KERNEL|__GFP_ZERO);
+	if (!vcpu->arch.shared)
+		goto uninit_vcpu;
+
 	vcpu->arch.host_retip = kvm_return_point;
 	vcpu->arch.host_msr = mfmsr();
 #ifdef CONFIG_PPC_BOOK3S_64
···
 
 	err = kvmppc_mmu_init(vcpu);
 	if (err < 0)
-		goto free_shadow_vcpu;
+		goto uninit_vcpu;
 
 	return vcpu;
 
+uninit_vcpu:
+	kvm_vcpu_uninit(vcpu);
 free_shadow_vcpu:
 	kfree(vcpu_book3s->shadow_vcpu);
 free_vcpu:
···
 {
 	struct kvmppc_vcpu_book3s *vcpu_book3s = to_book3s(vcpu);
 
+	free_page((unsigned long)vcpu->arch.shared);
 	kvm_vcpu_uninit(vcpu);
 	kfree(vcpu_book3s->shadow_vcpu);
 	vfree(vcpu_book3s);

arch/powerpc/kvm/e500.c

···
 	if (err)
 		goto uninit_vcpu;
 
+	vcpu->arch.shared = (void*)__get_free_page(GFP_KERNEL|__GFP_ZERO);
+	if (!vcpu->arch.shared)
+		goto uninit_tlb;
+
 	return vcpu;
 
+uninit_tlb:
+	kvmppc_e500_tlb_uninit(vcpu_e500);
 uninit_vcpu:
 	kvm_vcpu_uninit(vcpu);
 free_vcpu:
···
 {
 	struct kvmppc_vcpu_e500 *vcpu_e500 = to_e500(vcpu);
 
+	free_page((unsigned long)vcpu->arch.shared);
 	kvmppc_e500_tlb_uninit(vcpu_e500);
 	kvm_vcpu_uninit(vcpu);
 	kmem_cache_free(kvm_vcpu_cache, vcpu_e500);