[Qemu-devel] [PATCH 0/2] s390x/kvm: ioctl for reading and writing from/to guest memory

[Qemu-devel] [PATCH 0/2] s390x/kvm: ioctl for reading and writing from/to guest memory

[Thomas Huth]

These two patches enable QEMU to make use of the new KVM_GUEST_MEM_OP
ioctl on s390x (see my kernel patch with the title "KVM: s390: Add MEMOP
ioctls for reading/writing guest memory" that I've posted on the KVM
mailing list).
The first patch in this series updates the Linux headers with the new
ioctl definitions. This should be replaced with a proper synchronized
header update against kvm/next as soon as the kernel part has been
accepted.
The second patch then uses the ioctl when QEMU has to access the logical
memory of a guest. This patch goes on top of my "s390x: rework guest
memory access" patch series that has been sent out to the qemu-devel list
by Jens Freimann on last thursday.

Thomas Huth (2):
  Update Linux headers with KVM_GUEST_MEM_OP ioctl
  s390x/mmu: Use ioctl for reading and writing from/to guest memory

 linux-headers/linux/kvm.h |   21 +++++++++++++++++++++
 target-s390x/cpu.h        |    7 +++++++
 target-s390x/kvm.c        |   35 +++++++++++++++++++++++++++++++++++
 target-s390x/mmu_helper.c |    9 +++++++++
 4 files changed, 72 insertions(+), 0 deletions(-)

[Qemu-devel] [PATCH 1/2] Update Linux headers with KVM_GUEST_MEM_OP ioctl

[Thomas Huth]

Synchronized the kvm.h Linux header for the new ioctl.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
---
 linux-headers/linux/kvm.h |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
index 12045a1..a5f2c8e 100644
--- a/linux-headers/linux/kvm.h
+++ b/linux-headers/linux/kvm.h
@@ -365,6 +365,23 @@ struct kvm_translation {
 	__u8  pad[5];
 };
 
+/* for KVM_S390_MEM_OP */
+struct kvm_s390_mem_op {
+	/* in */
+	__u64 gaddr;		/* the guest address */
+	__u64 flags;		/* arch specific flags */
+	__u32 size;		/* amount of bytes */
+	__u32 op;		/* type of operation */
+	__u64 buf;		/* buffer in userspace */
+	__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
+/* 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)
+
 /* for KVM_INTERRUPT */
 struct kvm_interrupt {
 	/* in */
@@ -761,6 +778,8 @@ struct kvm_ppc_smmu_info {
 #define KVM_CAP_PPC_FIXUP_HCALL 103
 #define KVM_CAP_PPC_ENABLE_HCALL 104
 #define KVM_CAP_CHECK_EXTENSION_VM 105
+#define KVM_CAP_S390_USER_SIGP 106
+#define KVM_CAP_S390_MEM_OP 107
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -1137,6 +1156,8 @@ struct kvm_s390_ucas_mapping {
 #define KVM_ARM_VCPU_INIT	  _IOW(KVMIO,  0xae, struct kvm_vcpu_init)
 #define KVM_ARM_PREFERRED_TARGET  _IOR(KVMIO,  0xaf, struct kvm_vcpu_init)
 #define KVM_GET_REG_LIST	  _IOWR(KVMIO, 0xb0, struct kvm_reg_list)
+/* Available with KVM_CAP_S390_MEM_OP */
+#define KVM_S390_MEM_OP		  _IOW(KVMIO,  0xb1, struct kvm_s390_mem_op)
 
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
 #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
-- 
1.7.1

[Qemu-devel] [PATCH 2/2] s390x/mmu: Use ioctl for reading and writing from/to guest memory

[Thomas Huth]

Add code to make use of the new ioctl for reading from / writing to
virtual guest memory. By using the ioctl, the memory accesses are now
protected with the so-called ipte-lock in the kernel.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
---
 target-s390x/cpu.h        |    7 +++++++
 target-s390x/kvm.c        |   35 +++++++++++++++++++++++++++++++++++
 target-s390x/mmu_helper.c |    9 +++++++++
 3 files changed, 51 insertions(+), 0 deletions(-)

diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index b6b4632..cffdd1b 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -394,6 +394,8 @@ void kvm_s390_service_interrupt(uint32_t parm);
 void kvm_s390_vcpu_interrupt(S390CPU *cpu, struct kvm_s390_irq *irq);
 void kvm_s390_floating_interrupt(struct kvm_s390_irq *irq);
 int kvm_s390_inject_flic(struct kvm_s390_irq *irq);
+int kvm_s390_mem_op(S390CPU *cpu, vaddr addr, void *hostbuf, int len,
+                    bool is_write);
 void kvm_s390_access_exception(S390CPU *cpu, uint16_t code, uint64_t te_code);
 #else
 static inline void kvm_s390_virtio_irq(int config_change, uint64_t token)
@@ -402,6 +404,11 @@ static inline void kvm_s390_virtio_irq(int config_change, uint64_t token)
 static inline void kvm_s390_service_interrupt(uint32_t parm)
 {
 }
+static inline int kvm_s390_mem_op(S390CPU *cpu, vaddr addr, void *hostbuf,
+                                  int len, bool is_write)
+{
+    return -ENOSYS;
+}
 static inline void kvm_s390_access_exception(S390CPU *cpu, uint16_t code,
                                              uint64_t te_code)
 {
diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c
index 195493c..57a3aa1 100644
--- a/target-s390x/kvm.c
+++ b/target-s390x/kvm.c
@@ -117,6 +117,7 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
 
 static int cap_sync_regs;
 static int cap_async_pf;
+static int cap_mem_op;
 
 static void *legacy_s390_alloc(size_t size, uint64_t *align);
 
@@ -176,6 +177,7 @@ int kvm_arch_init(KVMState *s)
 {
     cap_sync_regs = kvm_check_extension(s, KVM_CAP_SYNC_REGS);
     cap_async_pf = kvm_check_extension(s, KVM_CAP_ASYNC_PF);
+    cap_mem_op = kvm_check_extension(s, KVM_CAP_S390_MEM_OP);
 
     if (kvm_check_extension(s, KVM_CAP_VM_ATTRIBUTES)) {
         kvm_s390_enable_cmma(s);
@@ -436,6 +438,39 @@ int kvm_arch_get_registers(CPUState *cs)
     return 0;
 }
 
+/**
+ * kvm_s390_mem_op:
+ * @addr:      the logical start address in guest memory
+ * @hostbuf:   buffer in host memory. NULL = do only checks w/o copying
+ * @len:       length that should be transfered
+ * @is_write:  true = write, false = read
+ * Returns:    0 on success, non-zero if an exception or error occured
+ *
+ * Use KVM ioctl to read/write from/to guest memory. An access exception
+ * is injected into the vCPU in case of translation errors.
+ */
+int kvm_s390_mem_op(S390CPU *cpu, vaddr addr, void *hostbuf, int len,
+                    bool is_write)
+{
+    struct kvm_s390_mem_op mem_op = {
+        .gaddr = addr,
+        .flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION,
+        .size = len,
+        .op = is_write ? KVM_S390_MEMOP_LOGICAL_WRITE
+                       : KVM_S390_MEMOP_LOGICAL_READ,
+        .buf = (uint64_t)hostbuf,
+    };
+
+    if (!cap_mem_op) {
+        return -ENOSYS;
+    }
+    if (!hostbuf) {
+        mem_op.flags |= KVM_S390_MEMOP_F_CHECK_ONLY;
+    }
+
+    return kvm_vcpu_ioctl(CPU(cpu), KVM_S390_MEM_OP, &mem_op);
+}
+
 /*
  * Legacy layout for s390:
  * Older S390 KVM requires the topmost vma of the RAM to be
diff --git a/target-s390x/mmu_helper.c b/target-s390x/mmu_helper.c
index b061c85..22f965a 100644
--- a/target-s390x/mmu_helper.c
+++ b/target-s390x/mmu_helper.c
@@ -450,6 +450,15 @@ int s390_cpu_virt_mem_rw(S390CPU *cpu, vaddr laddr, void *hostbuf,
     target_ulong *pages;
     int ret;
 
+    if (kvm_enabled()) {
+        ret = kvm_s390_mem_op(cpu, laddr, hostbuf, len, is_write);
+        if (ret >= 0) {
+            return ret;
+        } else if (ret != -ENOSYS) {
+            error_printf("kvm_s390_mem_op() failed: %s\n", strerror(-ret));
+        }
+    }
+
     nr_pages = (((laddr & ~TARGET_PAGE_MASK) + len - 1) >> TARGET_PAGE_BITS)
                + 1;
     pages = g_malloc(nr_pages * sizeof(*pages));
-- 
1.7.1