On 03/02/2015 13:11, Thomas Huth wrote:
> On s390, we've got to make sure to hold the IPTE lock while accessing
> virtual memory. So let's add an ioctl for reading and writing virtual
> memory to provide this feature for userspace, too.
>
> Signed-off-by: Thomas Huth <thuth@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: Dominik Dingel <dingel@xxxxxxxxxxxxxxxxxx>
> Reviewed-by: David Hildenbrand <dahi@xxxxxxxxxxxxxxxxxx>
> ---
> Documentation/virtual/kvm/api.txt | 44 +++++++++++++++++++++++++
> arch/s390/kvm/gaccess.c | 22 +++++++++++++
> arch/s390/kvm/gaccess.h | 2 +
> arch/s390/kvm/kvm-s390.c | 63 +++++++++++++++++++++++++++++++++++++
> include/uapi/linux/kvm.h | 21 ++++++++++++
> 5 files changed, 152 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index b112efc..bf44b53 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2716,6 +2716,50 @@ The fields in each entry are defined as follows:
> eax, ebx, ecx, edx: the values returned by the cpuid instruction for
> this function/index combination
>
> +4.89 KVM_GUEST_MEM_OP
> +
> +Capability: KVM_CAP_MEM_OP
Put "virtual" somewhere in the ioctl name and capability?
> +Architectures: s390
> +Type: vcpu ioctl
> +Parameters: struct kvm_guest_mem_op (in)
> +Returns: = 0 on success,
> + < 0 on generic error (e.g. -EFAULT or -ENOMEM),
> + > 0 if an exception occurred while walking the page tables
> +
> +Read or write data from/to the virtual memory of a VPCU.
> +
> +Parameters are specified via the following structure:
> +
> +struct kvm_guest_mem_op {
> + __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 */
> +};
> +
> +The type of operation is specified in the "op" field, either KVM_MEMOP_VIRTREAD
> +for reading from memory, KVM_MEMOP_VIRTWRITE for writing to memory, or
> +KVM_MEMOP_CHECKVIRTREAD or KVM_MEMOP_CHECKVIRTWRITE to check whether the
Better:
#define KVM_MEMOP_READ 0
#define KVM_MEMOP_WRITE 1
and in the flags field:
#define KVM_MEMOP_F_CHECK_ONLY (1 << 1)
> +corresponding memory access would create an access exception (without
> +changing the data in the memory at the destination). In case an access
> +exception occurred while walking the MMU tables of the guest, the ioctl
> +returns a positive error number to indicate the type of exception. The
> +exception is raised directly at the corresponding VCPU if the bit
> +KVM_MEMOP_F_INJECT_EXC is set in the "flags" field.
KVM_MEMOP_F_INJECT_EXCEPTION.
> +The logical (virtual) start address of the memory region has to be specified
> +in the "gaddr" field, and the length of the region in the "size" field.
> +"buf" is the buffer supplied by the userspace application where the read data
> +should be written to for KVM_MEMOP_VIRTREAD, or where the data that should
> +be written is stored for a KVM_MEMOP_VIRTWRITE. "buf" can be NULL for both
> +CHECK operations.
"buf" is unused and can be NULL for both CHECK operations.
> +The "reserved" field is meant for future extensions. It must currently be
> +set to 0.
Not really true, as you don't check it. So "It is not used by KVM with
the currently defined set of flags" is a better explanation.
Paolo
> +
> 5. The kvm_run structure
> ------------------------
>
> diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
> index 8a1be90..d912362 100644
> --- a/arch/s390/kvm/gaccess.c
> +++ b/arch/s390/kvm/gaccess.c
> @@ -697,6 +697,28 @@ int guest_translate_address(struct kvm_vcpu *vcpu, unsigned long gva,
> }
>
> /**
> + * check_gva_range - test a range of guest virtual addresses for accessibility
> + */
> +int check_gva_range(struct kvm_vcpu *vcpu, unsigned long gva,
> + unsigned long length, int is_write)
> +{
> + unsigned long gpa;
> + unsigned long currlen;
> + int rc = 0;
> +
> + ipte_lock(vcpu);
> + while (length > 0 && !rc) {
> + currlen = min(length, PAGE_SIZE - (gva % PAGE_SIZE));
> + rc = guest_translate_address(vcpu, gva, &gpa, is_write);
> + gva += currlen;
> + length -= currlen;
> + }
> + ipte_unlock(vcpu);
> +
> + return rc;
> +}
> +
> +/**
> * kvm_s390_check_low_addr_protection - check for low-address protection
> * @ga: Guest address
> *
> diff --git a/arch/s390/kvm/gaccess.h b/arch/s390/kvm/gaccess.h
> index 0149cf1..268beb7 100644
> --- a/arch/s390/kvm/gaccess.h
> +++ b/arch/s390/kvm/gaccess.h
> @@ -157,6 +157,8 @@ int read_guest_lc(struct kvm_vcpu *vcpu, unsigned long gra, void *data,
>
> int guest_translate_address(struct kvm_vcpu *vcpu, unsigned long gva,
> unsigned long *gpa, int write);
> +int check_gva_range(struct kvm_vcpu *vcpu, unsigned long gva,
> + unsigned long length, int is_write);
>
> int access_guest(struct kvm_vcpu *vcpu, unsigned long ga, void *data,
> unsigned long len, int write);
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index b2371c0..c80a640 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -168,6 +168,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_VM_ATTRIBUTES:
> case KVM_CAP_MP_STATE:
> case KVM_CAP_S390_USER_SIGP:
> + case KVM_CAP_MEM_OP:
> r = 1;
> break;
> case KVM_CAP_NR_VCPUS:
> @@ -1886,6 +1887,59 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
> return r;
> }
>
> +static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
> + struct kvm_guest_mem_op *mop)
> +{
> + void __user *uaddr = (void __user *)mop->buf;
> + void *tmpbuf = NULL;
> + int r, srcu_idx;
> +
> + if ((mop->flags & ~KVM_MEMOP_F_INJECT_EXC) != 0)
> + return -EINVAL;
> +
> + if (mop->op == KVM_MEMOP_VIRTREAD || mop->op == KVM_MEMOP_VIRTWRITE) {
> + if (mop->size > 16 * PAGE_SIZE)
> + return -E2BIG;
> + tmpbuf = vmalloc(mop->size);
> + if (!tmpbuf)
> + return -ENOMEM;
> + }
> +
> + srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
> +
> + switch (mop->op) {
> + case KVM_MEMOP_VIRTREAD:
> + r = read_guest(vcpu, mop->gaddr, tmpbuf, mop->size);
> + if (r == 0) {
> + if (copy_to_user(uaddr, tmpbuf, mop->size))
> + r = -EFAULT;
> + }
> + break;
> + case KVM_MEMOP_VIRTWRITE:
> + if (copy_from_user(tmpbuf, uaddr, mop->size)) {
> + r = -EFAULT;
> + break;
> + }
> + r = write_guest(vcpu, mop->gaddr, tmpbuf, mop->size);
> + break;
> + case KVM_MEMOP_CHECKVIRTREAD:
> + case KVM_MEMOP_CHECKVIRTWRITE:
> + r = check_gva_range(vcpu, mop->gaddr, mop->size,
> + mop->op == KVM_MEMOP_CHECKVIRTWRITE);
> + break;
> + default:
> + r = -EINVAL;
> + }
> +
> + srcu_read_unlock(&vcpu->kvm->srcu, srcu_idx);
> +
> + if (r > 0 && (mop->flags & KVM_MEMOP_F_INJECT_EXC) != 0)
> + kvm_s390_inject_prog_irq(vcpu, &vcpu->arch.pgm);
> +
> + vfree(tmpbuf);
> + return r;
> +}
> +
> long kvm_arch_vcpu_ioctl(struct file *filp,
> unsigned int ioctl, unsigned long arg)
> {
> @@ -1985,6 +2039,15 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
> r = kvm_vcpu_ioctl_enable_cap(vcpu, &cap);
> break;
> }
> + case KVM_GUEST_MEM_OP: {
> + struct kvm_guest_mem_op mem_op;
> +
> + if (copy_from_user(&mem_op, argp, sizeof(mem_op)) == 0)
> + r = kvm_s390_guest_mem_op(vcpu, &mem_op);
> + else
> + r = -EFAULT;
> + break;
> + }
> default:
> r = -ENOTTY;
> }
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8055706..528a3d4 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -365,6 +365,24 @@ struct kvm_translation {
> __u8 pad[5];
> };
>
> +/* for KVM_GUEST_MEM_OP */
> +struct kvm_guest_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_guest_mem_op->op */
> +#define KVM_MEMOP_VIRTREAD 0
> +#define KVM_MEMOP_VIRTWRITE 1
> +#define KVM_MEMOP_CHECKVIRTREAD 2
> +#define KVM_MEMOP_CHECKVIRTWRITE 3
> +/* flags for kvm_guest_mem_op->flags */
> +#define KVM_MEMOP_F_INJECT_EXC 0x0001UL /* Inject exception on faults */
> +
> /* for KVM_INTERRUPT */
> struct kvm_interrupt {
> /* in */
> @@ -760,6 +778,7 @@ struct kvm_ppc_smmu_info {
> #define KVM_CAP_PPC_ENABLE_HCALL 104
> #define KVM_CAP_CHECK_EXTENSION_VM 105
> #define KVM_CAP_S390_USER_SIGP 106
> +#define KVM_CAP_MEM_OP 107
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> @@ -1135,6 +1154,8 @@ 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_MEM_OP */
> +#define KVM_GUEST_MEM_OP _IOW(KVMIO, 0xb1, struct kvm_guest_mem_op)
>
> #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)
> #define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1)
>
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