Re: [PATCH v3 05/10] KVM: s390: Add optional storage key checking to MEMOP IOCTL

Janosch Frank
2022-02-11T08:53:39Z

On 2/10/22 10:29, Christian Borntraeger wrote:
> Am 09.02.22 um 18:04 schrieb Janis Schoetterl-Glausch:
>> User space needs a mechanism to perform key checked accesses when
>> emulating instructions.
>>
>> The key can be passed as an additional argument.
>> Having an additional argument is flexible, as user space can
>> pass the guest PSW's key, in order to make an access the same way the
>> CPU would, or pass another key if necessary.
>>
>> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
>> Acked-by: Janosch Frank <frankja@linux.ibm.com>
>> Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
>
> Claudio, Janosch, can you confirm that this is still valid?

Reviewed-by: Janosch Frank <frankja@linux.ibm.com>

>
>
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
>
> minor thing below
>> ---
>> arch/s390/kvm/kvm-s390.c | 30 ++++++++++++++++++++----------
>> include/uapi/linux/kvm.h | 6 +++++-
>> 2 files changed, 25 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index cf347e1a4f17..85763ec7bc60 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -32,6 +32,7 @@
>> #include <linux/sched/signal.h>
>> #include <linux/string.h>
>> #include <linux/pgtable.h>
>> +#include <linux/bitfield.h>
>
> do we still need that after the changes?
>
>>
>> #include <asm/asm-offsets.h>
>> #include <asm/lowcore.h>
>> @@ -2359,6 +2360,11 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd)
>> return r;
>> }
>>
>> +static bool access_key_invalid(u8 access_key)
>> +{
>> + return access_key > 0xf;
>> +}
>> +
>> long kvm_arch_vm_ioctl(struct file *filp,
>> unsigned int ioctl, unsigned long arg)
>> {
>> @@ -4690,17 +4696,19 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
>> void *tmpbuf = NULL;
>> int r = 0;
>> const u64 supported_flags = KVM_S390_MEMOP_F_INJECT_EXCEPTION
>> - | KVM_S390_MEMOP_F_CHECK_ONLY;
>> + | KVM_S390_MEMOP_F_CHECK_ONLY
>> + | KVM_S390_MEMOP_F_SKEY_PROTECTION;
>>
>> if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size)
>> return -EINVAL;
>> -
>> if (mop->size > MEM_OP_MAX_SIZE)
>> return -E2BIG;
>> -
>> if (kvm_s390_pv_cpu_is_protected(vcpu))
>> return -EINVAL;
>> -

You want to make it look like the sida op?
Personally I'd leave it as is.

>> + if (mop->flags & KVM_S390_MEMOP_F_SKEY_PROTECTION) {
>> + if (access_key_invalid(mop->key))
>> + return -EINVAL;
>> + }
>> if (!(mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY)) {
>> tmpbuf = vmalloc(mop->size);
>> if (!tmpbuf)
>> @@ -4710,11 +4718,12 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
>> switch (mop->op) {
>> case KVM_S390_MEMOP_LOGICAL_READ:
>> if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) {
>> - r = check_gva_range(vcpu, mop->gaddr, mop->ar,
>> - mop->size, GACC_FETCH, 0);
>> + r = check_gva_range(vcpu, mop->gaddr, mop->ar, mop->size,
>> + GACC_FETCH, mop->key);
>> break;
>> }
>> - r = read_guest(vcpu, mop->gaddr, mop->ar, tmpbuf, mop->size);
>> + r = read_guest_with_key(vcpu, mop->gaddr, mop->ar, tmpbuf,
>> + mop->size, mop->key);
>> if (r == 0) {
>> if (copy_to_user(uaddr, tmpbuf, mop->size))
>> r = -EFAULT;
>> @@ -4722,15 +4731,16 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu,
>> break;
>> case KVM_S390_MEMOP_LOGICAL_WRITE:
>> if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) {
>> - r = check_gva_range(vcpu, mop->gaddr, mop->ar,
>> - mop->size, GACC_STORE, 0);
>> + r = check_gva_range(vcpu, mop->gaddr, mop->ar, mop->size,
>> + GACC_STORE, mop->key);
>> break;
>> }
>> if (copy_from_user(tmpbuf, uaddr, mop->size)) {
>> r = -EFAULT;
>> break;
>> }
>> - r = write_guest(vcpu, mop->gaddr, mop->ar, tmpbuf, mop->size);
>> + r = write_guest_with_key(vcpu, mop->gaddr, mop->ar, tmpbuf,
>> + mop->size, mop->key);
>> break;
>> }
>>
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index b46bcdb0cab1..44558cf4c52e 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -562,7 +562,10 @@ struct kvm_s390_mem_op {
>> __u32 op; /* type of operation */
>> __u64 buf; /* buffer in userspace */
>> union {
>> - __u8 ar; /* the access register number */
>> + struct {
>> + __u8 ar; /* the access register number */
>> + __u8 key; /* access key, ignored if flag unset */
>> + };
>> __u32 sida_offset; /* offset into the sida */
>> __u8 reserved[32]; /* should be set to 0 */
>> };
>> @@ -575,6 +578,7 @@ struct kvm_s390_mem_op {
>> /* 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)
>> +#define KVM_S390_MEMOP_F_SKEY_PROTECTION (1ULL << 2)
>>
>> /* for KVM_INTERRUPT */
>> struct kvm_interrupt {