[RFCv2.1] KVM: S390: protvirt: Introduce instruction data area bounce buffer

[Christian Borntraeger <borntraeger@de.ibm.com>]

From: Janosch Frank <frankja@linux.ibm.com>

Now that we can't access guest memory anymore, we have a dedicated
sattelite block that's a bounce buffer for instruction data.

We re-use the memop interface to copy the instruction data to / from
userspace. This lets us re-use a lot of QEMU code which used that
interface to make logical guest memory accesses which are not possible
anymore in protected mode anyway.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
---
 arch/s390/include/asm/kvm_host.h | 11 ++++++-
 arch/s390/kvm/kvm-s390.c         | 49 ++++++++++++++++++++++++++++++++
 arch/s390/kvm/pv.c               |  9 ++++++
 include/uapi/linux/kvm.h         | 10 +++++--
 4 files changed, 76 insertions(+), 3 deletions(-)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 9d7b248dcadc..2fe8d3c81951 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -127,6 +127,12 @@ struct mcck_volatile_info {
 #define CR14_INITIAL_MASK (CR14_UNUSED_32 | CR14_UNUSED_33 | \
 			   CR14_EXTERNAL_DAMAGE_SUBMASK)
 
+#define SIDAD_SIZE_MASK		0xff
+#define sida_origin(sie_block) \
+	(sie_block->sidad & PAGE_MASK)
+#define sida_size(sie_block) \
+	(((sie_block->sidad & SIDAD_SIZE_MASK) + 1) * PAGE_SIZE)
+
 #define CPUSTAT_STOPPED    0x80000000
 #define CPUSTAT_WAIT       0x10000000
 #define CPUSTAT_ECALL_PEND 0x08000000
@@ -315,7 +321,10 @@ struct kvm_s390_sie_block {
 #define CRYCB_FORMAT2 0x00000003
 	__u32	crycbd;			/* 0x00fc */
 	__u64	gcr[16];		/* 0x0100 */
-	__u64	gbea;			/* 0x0180 */
+	union {
+		__u64	gbea;			/* 0x0180 */
+		__u64	sidad;
+	};
 	__u8    reserved188[8];		/* 0x0188 */
 	__u64   sdnxo;			/* 0x0190 */
 	__u8    reserved198[8];		/* 0x0198 */
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 6f90d16cad92..56488f9ed190 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4435,6 +4435,41 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
 	return r;
 }
 
+static long kvm_s390_guest_sida_op(struct kvm_vcpu *vcpu,
+				   struct kvm_s390_mem_op *mop)
+{
+	void __user *uaddr = (void __user *)mop->buf;
+	int r = 0;
+
+	if (mop->flags || !mop->size)
+		return -EINVAL;
+
+	if (mop->size > sida_size(vcpu->arch.sie_block))
+		return -E2BIG;
+
+	if (mop->sida_offset > sida_size(vcpu->arch.sie_block))
+		return -E2BIG;
+
+	if (mop->size + mop->sida_offset > sida_size(vcpu->arch.sie_block))
+		return -E2BIG;
+
+	switch (mop->op) {
+	case KVM_S390_MEMOP_SIDA_READ:
+		r = 0;
+		if (copy_to_user(uaddr, (void *)(sida_origin(vcpu->arch.sie_block) +
+				 mop->sida_offset), mop->size))
+			r = -EFAULT;
+
+		break;
+	case KVM_S390_MEMOP_SIDA_WRITE:
+		r = 0;
+		if (copy_from_user((void *)(sida_origin(vcpu->arch.sie_block) +
+				   mop->sida_offset), uaddr, mop->size))
+			r = -EFAULT;
+		break;
+	}
+	return r;
+}
 static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
 				  struct kvm_s390_mem_op *mop)
 {
@@ -4444,6 +4479,8 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
 	const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION
 				    | KVM_S390_MEMOP_F_CHECK_ONLY;
 
+
+	BUILD_BUG_ON(sizeof(*mop) != 64);
 	if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size)
 		return -EINVAL;
 
@@ -4460,6 +4497,10 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
 
 	switch (mop->op) {
 	case KVM_S390_MEMOP_LOGICAL_READ:
+		if (kvm_s390_pv_is_protected(vcpu->kvm)) {
+			r = -EINVAL;
+			break;
+		}
 		if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) {
 			r = check_gva_range(vcpu, mop->gaddr, mop->ar,
 					    mop->size, GACC_FETCH);
@@ -4472,6 +4513,10 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
 		}
 		break;
 	case KVM_S390_MEMOP_LOGICAL_WRITE:
+		if (kvm_s390_pv_is_protected(vcpu->kvm)) {
+			r = -EINVAL;
+			break;
+		}
 		if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) {
 			r = check_gva_range(vcpu, mop->gaddr, mop->ar,
 					    mop->size, GACC_STORE);
@@ -4483,6 +4528,10 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
 		}
 		r = write_guest(vcpu, mop->gaddr, mop->ar, tmpbuf, mop->size);
 		break;
+	case KVM_S390_MEMOP_SIDA_READ:
+	case KVM_S390_MEMOP_SIDA_WRITE:
+		r = kvm_s390_guest_sida_op(vcpu, mop);
+		break;
 	default:
 		r = -EINVAL;
 	}
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 05e5ca8eab4f..d6345a0e348c 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -93,6 +93,7 @@ int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu)
 
 	free_pages(vcpu->arch.pv.stor_base,
 		   get_order(uv_info.guest_cpu_stor_len));
+	free_page(sida_origin(vcpu->arch.sie_block));
 	vcpu->arch.sie_block->pv_handle_cpu = 0;
 	vcpu->arch.sie_block->pv_handle_config = 0;
 	memset(&vcpu->arch.pv, 0, sizeof(vcpu->arch.pv));
@@ -122,6 +123,14 @@ int kvm_s390_pv_create_cpu(struct kvm_vcpu *vcpu)
 	uvcb.state_origin = (u64)vcpu->arch.sie_block;
 	uvcb.stor_origin = (u64)vcpu->arch.pv.stor_base;
 
+	/* Alloc Secure Instruction Data Area Designation */
+	vcpu->arch.sie_block->sidad = __get_free_page(GFP_KERNEL | __GFP_ZERO);
+	if (!vcpu->arch.sie_block->sidad) {
+		free_pages(vcpu->arch.pv.stor_base,
+			   get_order(uv_info.guest_cpu_stor_len));
+		return -ENOMEM;
+	}
+
 	rc = uv_call(0, (u64)&uvcb);
 	VCPU_EVENT(vcpu, 3, "PROTVIRT CREATE VCPU: cpu %d handle %llx rc %x rrc %x",
 		   vcpu->vcpu_id, uvcb.cpu_handle, uvcb.header.rc,
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index eab741bc12c3..a772771baf9f 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -466,7 +466,7 @@ struct kvm_translation {
 	__u8  pad[5];
 };
 
-/* for KVM_S390_MEM_OP */
+/* for KVM_S390_MEM_OP and KVM_S390_SIDA_OP */
 struct kvm_s390_mem_op {
 	/* in */
 	__u64 gaddr;		/* the guest address */
@@ -475,11 +475,17 @@ struct kvm_s390_mem_op {
 	__u32 op;		/* type of operation */
 	__u64 buf;		/* buffer in userspace */
 	__u8 ar;		/* the access register number */
-	__u8 reserved[31];	/* should be set to 0 */
+	__u8 reserved21[3];	/* should be set to 0 */
+	__u32 sida_offset;	/* offset into the sida */
+	__u8 reserved28[24];	/* should be set to 0 */
 };
+
+
 /* types for kvm_s390_mem_op->op */
 #define KVM_S390_MEMOP_LOGICAL_READ	0
 #define KVM_S390_MEMOP_LOGICAL_WRITE	1
+#define KVM_S390_MEMOP_SIDA_READ	2
+#define KVM_S390_MEMOP_SIDA_WRITE	3
 /* flags for kvm_s390_mem_op->flags */
 #define KVM_S390_MEMOP_F_CHECK_ONLY		(1ULL << 0)
 #define KVM_S390_MEMOP_F_INJECT_EXCEPTION	(1ULL << 1)
-- 
2.24.0