[PATCH v4 18/36] KVM: S390: protvirt: Introduce instruction data area bounce buffer

Christian Borntraeger
2020-02-24T11:41:16Z

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

Now that we can't access guest memory anymore, we have a dedicated
satellite 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>
Reviewed-by: Thomas Huth <thuth@redhat.com>
[borntraeger@de.ibm.com: patch merging, splitting, fixing]
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
arch/s390/include/asm/kvm_host.h | 11 +++++-
arch/s390/kvm/kvm-s390.c | 65 ++++++++++++++++++++++++++++----
arch/s390/kvm/pv.c | 11 ++++++
include/uapi/linux/kvm.h | 9 ++++-
4 files changed, 85 insertions(+), 11 deletions(-)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 4fcbb055a565..aa945b101fff 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 93bf8f103f05..67a746b0f8b9 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4492,12 +4492,40 @@ 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 + mop->sida_offset < mop->size)
+ return -EINVAL;
+ if (mop->size + mop->sida_offset > sida_size(vcpu->arch.sie_block))
+ return -E2BIG;
+
+ switch (mop->op) {
+ case KVM_S390_MEMOP_SIDA_READ:
+ 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:
+ 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)
{
void __user *uaddr = (void __user *)mop->buf;
void *tmpbuf = NULL;
- int r, srcu_idx;
+ int r = 0;
const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION
| KVM_S390_MEMOP_F_CHECK_ONLY;

@@ -4512,8 +4540,8 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
if (!tmpbuf)
return -ENOMEM;
}
-
- srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
+ if (kvm_s390_pv_cpu_is_protected(vcpu))
+ return -EINVAL;

switch (mop->op) {
case KVM_S390_MEMOP_LOGICAL_READ:
@@ -4540,12 +4568,8 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
}
r = write_guest(vcpu, mop->gaddr, mop->ar, tmpbuf, mop->size);
break;
- default:
- r = -EINVAL;
}

- srcu_read_unlock(&vcpu->kvm->srcu, srcu_idx);
-
if (r > 0 && (mop->flags & KVM_S390_MEMOP_F_INJECT_EXCEPTION) != 0)
kvm_s390_inject_prog_irq(vcpu, &vcpu->arch.pgm);

@@ -4553,6 +4577,31 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
return r;
}

+static long kvm_s390_guest_memsida_op(struct kvm_vcpu *vcpu,
+ struct kvm_s390_mem_op *mop)
+{
+ int r, srcu_idx;
+
+ srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
+
+ switch (mop->op) {
+ case KVM_S390_MEMOP_LOGICAL_READ:
+ case KVM_S390_MEMOP_LOGICAL_WRITE:
+ r = kvm_s390_guest_mem_op(vcpu, mop);
+ break;
+ case KVM_S390_MEMOP_SIDA_READ:
+ case KVM_S390_MEMOP_SIDA_WRITE:
+ /* we are locked against sida going away by the vcpu->mutex */
+ r = kvm_s390_guest_sida_op(vcpu, mop);
+ break;
+ default:
+ r = -EINVAL;
+ }
+
+ srcu_read_unlock(&vcpu->kvm->srcu, srcu_idx);
+ return r;
+}
+
long kvm_arch_vcpu_async_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
@@ -4683,7 +4732,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
struct kvm_s390_mem_op mem_op;

if (copy_from_user(&mem_op, argp, sizeof(mem_op)) == 0)
- r = kvm_s390_guest_mem_op(vcpu, &mem_op);
+ r = kvm_s390_guest_memsida_op(vcpu, &mem_op);
else
r = -EFAULT;
break;
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 014e53a41ead..cd81a58349a9 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -33,10 +33,13 @@ int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc)
if (!cc)
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));
vcpu->arch.sie_block->sdf = 0;
+ vcpu->arch.sie_block->gbea = 1;
kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);

return cc;
@@ -64,6 +67,14 @@ int kvm_s390_pv_create_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc)
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;
+ }
+
cc = uv_call(0, (u64)&uvcb);
*rc = uvcb.header.rc;
*rrc = uvcb.header.rrc;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index ad69817f7792..f4cac1c09e97 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -474,12 +474,17 @@ struct kvm_s390_mem_op {
__u32 size; /* amount of bytes */
__u32 op; /* type of operation */
__u64 buf; /* buffer in userspace */
- __u8 ar; /* the access register number */
- __u8 reserved[31]; /* should be set to 0 */
+ union {
+ __u8 ar; /* the access register number */
+ __u32 sida_offset; /* offset into the sida */
+ __u8 reserved[32]; /* 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)
--
2.25.0