Messages in this thread | | | Date | Thu, 26 Jan 2023 14:02:15 +0100 | From | Janosch Frank <> | Subject | Re: [PATCH v6 08/14] KVM: s390: Move common code of mem_op functions into functions |
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On 1/26/23 07:48, Thomas Huth wrote: > On 25/01/2023 22.26, Janis Schoetterl-Glausch wrote: >> The vcpu and vm mem_op ioctl implementations share some functionality. >> Move argument checking and buffer allocation into functions and call >> them from both implementations. >> This allows code reuse in case of additional future mem_op operations. >> >> Suggested-by: Janosch Frank <frankja@linux.ibm.com> >> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com> >> --- >> arch/s390/kvm/kvm-s390.c | 80 +++++++++++++++++++++------------------- >> 1 file changed, 42 insertions(+), 38 deletions(-) >> >> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >> index e4890e04b210..e0dfaa195949 100644 >> --- a/arch/s390/kvm/kvm-s390.c >> +++ b/arch/s390/kvm/kvm-s390.c >> @@ -2764,24 +2764,44 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd) >> return r; >> } >> >> -static bool access_key_invalid(u8 access_key) >> +static int mem_op_validate_common(struct kvm_s390_mem_op *mop, u64 supported_flags) >> { >> - return access_key > 0xf; >> + if (mop->flags & ~supported_flags || !mop->size) >> + return -EINVAL; >> + if (mop->size > MEM_OP_MAX_SIZE) >> + return -E2BIG; >> + if (mop->flags & KVM_S390_MEMOP_F_SKEY_PROTECTION) { >> + if (mop->key > 0xf) >> + return -EINVAL; >> + } else { >> + mop->key = 0; >> + } >> + return 0; >> +} >> + >> +static void *mem_op_alloc_buf(struct kvm_s390_mem_op *mop) >> +{ >> + void *buf; >> + >> + if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) >> + return NULL; >> + buf = vmalloc(mop->size); >> + if (!buf) >> + return ERR_PTR(-ENOMEM); >> + return buf; >> } >> >> static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop) >> { >> void __user *uaddr = (void __user *)mop->buf; >> - u64 supported_flags; >> void *tmpbuf = NULL; > > You likely can now remove the "= NULL" here, I guess? > >> int r, srcu_idx; >> >> - supported_flags = KVM_S390_MEMOP_F_SKEY_PROTECTION >> - | KVM_S390_MEMOP_F_CHECK_ONLY; >> - if (mop->flags & ~supported_flags || !mop->size) >> - return -EINVAL; >> - if (mop->size > MEM_OP_MAX_SIZE) >> - return -E2BIG; >> + r = mem_op_validate_common(mop, KVM_S390_MEMOP_F_SKEY_PROTECTION | >> + KVM_S390_MEMOP_F_CHECK_ONLY); >> + if (r) >> + return r; >> + >> /* >> * This is technically a heuristic only, if the kvm->lock is not >> * taken, it is not guaranteed that the vm is/remains non-protected. >> @@ -2793,17 +2813,9 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop) >> */ >> if (kvm_s390_pv_get_handle(kvm)) >> return -EINVAL; >> - if (mop->flags & KVM_S390_MEMOP_F_SKEY_PROTECTION) { >> - if (access_key_invalid(mop->key)) >> - return -EINVAL; >> - } else { >> - mop->key = 0; >> - } >> - if (!(mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY)) { >> - tmpbuf = vmalloc(mop->size); >> - if (!tmpbuf) >> - return -ENOMEM; >> - } >> + tmpbuf = mem_op_alloc_buf(mop); >> + if (IS_ERR(tmpbuf)) >> + return PTR_ERR(tmpbuf); >> >> srcu_idx = srcu_read_lock(&kvm->srcu); >> >> @@ -5250,28 +5262,20 @@ static long kvm_s390_vcpu_mem_op(struct kvm_vcpu *vcpu, >> { >> void __user *uaddr = (void __user *)mop->buf; >> void *tmpbuf = NULL; > > ... and here, too. > > But I have to admit that I'm also not sure whether I like the > mem_op_alloc_buf() part or not (the mem_op_validate_common() part looks fine > to me) : mem_op_alloc_buf() is a new function with 11 lines of code, and the > old spots that allocate memory were only 5 lines of code each, so you now > increased the LoC count and additionally have to fiddly with IS_ERR and > PTR_ERR which is always a little bit ugly in my eyes ... IMHO I'd rather > keep the old code here. But that's just my 0.02 €, if you think it's nicer > with mem_op_alloc_buf(), I won't insist on keeping the old code. > > Thomas >
I've done a PoC that has a **buff argument and combines the check with the alloc.
@Nina: Any reason why this was split up?
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