Messages in this thread Patch in this message | | | Date | Tue, 18 Jan 2022 12:51:26 +0100 | Subject | Re: [RFC PATCH v1 05/10] KVM: s390: Add optional storage key checking to MEMOP IOCTL | From | Christian Borntraeger <> |
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Am 18.01.22 um 10:52 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 via the flags field. > As reserved flags need to be 0, and key 0 matches all storage keys, > by default no key checking is performed, as before. > 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> > --- > arch/s390/kvm/kvm-s390.c | 21 ++++++++++++++------- > include/uapi/linux/kvm.h | 1 + > 2 files changed, 15 insertions(+), 7 deletions(-) > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index 38b304e81c57..c4acdb025ff1 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> > > #include <asm/asm-offsets.h> > #include <asm/lowcore.h> > @@ -4727,9 +4728,11 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu, > { > void __user *uaddr = (void __user *)mop->buf; > void *tmpbuf = NULL; > + char access_key = 0; > 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_SKEYS_ACC;
I think it would be better to just have a flag here (single bit) to check the key and then embed the key value in the payload.
union { __u8 ar; /* the access register number */ __u32 sida_offset; /* offset into the sida */ __u8 reserved[32]; /* should be set to 0 */ };
There are cases when we need both, AR and key so maybe an unname struct is the easiest.
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 1daa45268de2..e8fa1f82d472 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; /* effective storage key */ + }; __u32 sida_offset; /* offset into the sida */ __u8 reserved[32]; /* should be set to 0 */ }; (or acc instead of key)
> > if (mop->flags & ~supported_flags || mop->ar >= NUM_ACRS || !mop->size) > return -EINVAL; > @@ -4746,14 +4749,17 @@ static long kvm_s390_guest_mem_op(struct kvm_vcpu *vcpu, > return -ENOMEM; > } > > + access_key = FIELD_GET(KVM_S390_MEMOP_F_SKEYS_ACC, mop->flags); > + > 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, access_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, access_key); > if (r == 0) { > if (copy_to_user(uaddr, tmpbuf, mop->size)) > r = -EFAULT; > @@ -4761,15 +4767,16 @@ 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, access_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, access_key); > break; > } > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index 1daa45268de2..e3f450b2f346 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -575,6 +575,7 @@ 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_SKEYS_ACC 0x0f00ULL > > /* for KVM_INTERRUPT */ > struct kvm_interrupt {
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