[RFC,v1,06/10] KVM: s390: Add vm IOCTL for key checked guest absolute memory access

Message ID	20220118095210.1651483-7-scgl@linux.ibm.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <kvm-owner@kernel.org> From: Janis Schoetterl-Glausch <scgl@linux.ibm.com> To: Christian Borntraeger <borntraeger@linux.ibm.com>, Janosch Frank <frankja@linux.ibm.com>, Heiko Carstens <hca@linux.ibm.com>, Vasily Gorbik <gor@linux.ibm.com> Cc: Janis Schoetterl-Glausch <scgl@linux.ibm.com>, David Hildenbrand <david@redhat.com>, Claudio Imbrenda <imbrenda@linux.ibm.com>, Alexander Gordeev <agordeev@linux.ibm.com>, kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH v1 06/10] KVM: s390: Add vm IOCTL for key checked guest absolute memory access Date: Tue, 18 Jan 2022 10:52:06 +0100 Message-Id: <20220118095210.1651483-7-scgl@linux.ibm.com> In-Reply-To: <20220118095210.1651483-1-scgl@linux.ibm.com> References: <20220118095210.1651483-1-scgl@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk
Series	KVM: s390: Do storage key checking \| expand [RFC,v1,00/10] KVM: s390: Do storage key checking [RFC,v1,02/10] KVM: s390: Honor storage keys when accessing guest memory [RFC,v1,03/10] KVM: s390: handle_tprot: Honor storage keys [RFC,v1,04/10] KVM: s390: selftests: Test TEST PROTECTION emulation [RFC,v1,05/10] KVM: s390: Add optional storage key checking to MEMOP IOCTL [RFC,v1,06/10] KVM: s390: Add vm IOCTL for key checked guest absolute memory access [RFC,v1,07/10] KVM: s390: Rename existing vcpu memop functions [RFC,v1,08/10] KVM: s390: selftests: Test memops with storage keys [RFC,v1,09/10] KVM: s390: Add capability for storage key extension of MEM_OP IOCTL [RFC,v1,10/10] KVM: s390: selftests: Make use of capability in MEM_OP test

diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c index efe33cda38b6..db1d9a494f77 100644 --- a/arch/s390/kvm/gaccess.c +++ b/arch/s390/kvm/gaccess.c @@ -795,6 +795,35 @@ static int low_address_protection_enabled(struct kvm_vcpu *vcpu, return 1; } +static int vm_check_access_key(struct kvm *kvm, char access_key, + enum gacc_mode mode, gpa_t gpa) +{ + unsigned long hva; + unsigned char storage_key, access_control; + bool fetch_protected; + int r; + + if (access_key == 0) + return 0; + + hva = gfn_to_hva(kvm, gpa_to_gfn(gpa)); + if (kvm_is_error_hva(hva)) + return PGM_ADDRESSING; + + mmap_read_lock(current->mm); + r = get_guest_storage_key(current->mm, hva, &storage_key); + mmap_read_unlock(current->mm); + if (r) + return r; + access_control = FIELD_GET(_PAGE_ACC_BITS, storage_key); + if (access_control == access_key) + return 0; + fetch_protected = storage_key & _PAGE_FP_BIT; + if ((mode == GACC_FETCH || mode == GACC_IFETCH) && !fetch_protected) + return 0; + return PGM_PROTECTION; +} + static bool fetch_prot_override_applicable(struct kvm_vcpu *vcpu, enum gacc_mode mode, union asce asce) { @@ -990,6 +1019,26 @@ access_guest_page_with_key(struct kvm *kvm, enum gacc_mode mode, gpa_t gpa, return 0; } +int access_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, void *data, + unsigned long len, enum gacc_mode mode, char key) +{ + int offset = offset_in_page(gpa); + int fragment_len; + int rc; + + while (min(PAGE_SIZE - offset, len) > 0) { + fragment_len = min(PAGE_SIZE - offset, len); + rc = access_guest_page_with_key(kvm, mode, gpa, data, fragment_len, key); + if (rc) + return rc; + offset = 0; + len -= fragment_len; + data += fragment_len; + gpa += fragment_len; + } + return 0; +} + int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data, unsigned long len, enum gacc_mode mode, char access_key) @@ -1131,6 +1180,29 @@ int check_gva_range(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar, return rc; } +/** + * check_gpa_range - test a range of guest physical addresses for accessibility + * @kvm: virtual machine instance + * @gpa: guest physical address + * @length: length of test range + * @mode: access mode to test, relevant for storage keys + * @access_key: access key to mach the storage keys with + */ +int check_gpa_range(struct kvm *kvm, unsigned long gpa, unsigned long length, + enum gacc_mode mode, char access_key) +{ + unsigned int fragment_len; + int rc = 0; + + while (length && !rc) { + fragment_len = min(PAGE_SIZE - offset_in_page(gpa), length); + rc = vm_check_access_key(kvm, access_key, mode, gpa); + length -= fragment_len; + gpa += fragment_len; + } + return rc; +} + /** * kvm_s390_check_low_addr_prot_real - check for low-address protection * @vcpu: virtual cpu diff --git a/arch/s390/kvm/gaccess.h b/arch/s390/kvm/gaccess.h index 0d4416178bb6..d89178b92d51 100644 --- a/arch/s390/kvm/gaccess.h +++ b/arch/s390/kvm/gaccess.h @@ -194,6 +194,12 @@ int check_gva_range(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar, unsigned long length, enum gacc_mode mode, char access_key); +int check_gpa_range(struct kvm *kvm, unsigned long gpa, unsigned long length, + enum gacc_mode mode, char access_key); + +int access_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, void *data, + unsigned long len, enum gacc_mode mode, char key); + int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data, unsigned long len, enum gacc_mode mode, char access_key); diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index c4acdb025ff1..8dab956f84a6 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -2390,6 +2390,78 @@ static int kvm_s390_handle_pv(struct kvm *kvm, struct kvm_pv_cmd *cmd) return r; } +static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop) +{ + static const __u8 zeros[sizeof(mop->reserved)] = {0}; + void __user *uaddr = (void __user *)mop->buf; + u64 supported_flags; + void *tmpbuf = NULL; + char access_key; + int r, srcu_idx; + + access_key = FIELD_GET(KVM_S390_MEMOP_F_SKEYS_ACC, mop->flags); + supported_flags = KVM_S390_MEMOP_F_SKEYS_ACC + | KVM_S390_MEMOP_F_CHECK_ONLY; + if (mop->flags & ~supported_flags) + return -EINVAL; + if (mop->size > MEM_OP_MAX_SIZE) + return -E2BIG; + if (kvm_s390_pv_is_protected(kvm)) + return -EINVAL; + if (memcmp(mop->reserved, zeros, sizeof(zeros)) != 0) + return -EINVAL; + + if (!(mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY)) { + tmpbuf = vmalloc(mop->size); + if (!tmpbuf) + return -ENOMEM; + } + + srcu_idx = srcu_read_lock(&kvm->srcu); + + if (kvm_is_error_gpa(kvm, mop->gaddr)) { + r = PGM_ADDRESSING; + goto out_unlock; + } + + switch (mop->op) { + case KVM_S390_MEMOP_ABSOLUTE_READ: { + if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) { + r = check_gpa_range(kvm, mop->gaddr, mop->size, GACC_FETCH, access_key); + } else { + r = access_guest_abs_with_key(kvm, mop->gaddr, tmpbuf, + mop->size, GACC_FETCH, access_key); + if (r == 0) { + if (copy_to_user(uaddr, tmpbuf, mop->size)) + r = -EFAULT; + } + } + break; + } + case KVM_S390_MEMOP_ABSOLUTE_WRITE: { + if (mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY) { + r = check_gpa_range(kvm, mop->gaddr, mop->size, GACC_STORE, access_key); + } else { + if (copy_from_user(tmpbuf, uaddr, mop->size)) { + r = -EFAULT; + break; + } + r = access_guest_abs_with_key(kvm, mop->gaddr, tmpbuf, + mop->size, GACC_STORE, access_key); + } + break; + } + default: + r = -EINVAL; + } + +out_unlock: + srcu_read_unlock(&kvm->srcu, srcu_idx); + + vfree(tmpbuf); + return r; +} + long kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) { @@ -2514,6 +2586,15 @@ long kvm_arch_vm_ioctl(struct file *filp, } break; } + case KVM_S390_MEM_OP: { + struct kvm_s390_mem_op mem_op; + + if (copy_from_user(&mem_op, argp, sizeof(mem_op)) == 0) + r = kvm_s390_vm_mem_op(kvm, &mem_op); + else + r = -EFAULT; + break; + } default: r = -ENOTTY; } diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index e3f450b2f346..dd04170287fd 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -572,6 +572,8 @@ struct kvm_s390_mem_op { #define KVM_S390_MEMOP_LOGICAL_WRITE 1 #define KVM_S390_MEMOP_SIDA_READ 2 #define KVM_S390_MEMOP_SIDA_WRITE 3 +#define KVM_S390_MEMOP_ABSOLUTE_READ 4 +#define KVM_S390_MEMOP_ABSOLUTE_WRITE 5 /* 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)

[RFC,v1,06/10] KVM: s390: Add vm IOCTL for key checked guest absolute memory access

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