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Tue, 13 Dec 2022 16:54:12 +0000 (GMT) From: Janis Schoetterl-Glausch To: Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Heiko Carstens , Vasily Gorbik , Alexander Gordeev Cc: Janis Schoetterl-Glausch , David Hildenbrand , Jonathan Corbet , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-s390@vger.kernel.org, Paolo Bonzini , Shuah Khan , Sven Schnelle Subject: [PATCH v4 1/9] KVM: s390: Extend MEM_OP ioctl by storage key checked cmpxchg Date: Tue, 13 Dec 2022 17:53:57 +0100 Message-Id: <20221213165405.2953539-2-scgl@linux.ibm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20221213165405.2953539-1-scgl@linux.ibm.com> References: <20221213165405.2953539-1-scgl@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: Of0-r-MRYeXMM0TW2y4XjRzpAyEBPSnF X-Proofpoint-GUID: nWo9t8yz8Y0JhRNKgj8JLj_Xs5O6iow_ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.923,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-12-13_03,2022-12-13_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 lowpriorityscore=0 malwarescore=0 adultscore=0 clxscore=1015 priorityscore=1501 phishscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2210170000 definitions=main-2212130147 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org User space can use the MEM_OP ioctl to make storage key checked reads and writes to the guest, however, it has no way of performing atomic, key checked, accesses to the guest. Extend the MEM_OP ioctl in order to allow for this, by adding a cmpxchg mode. For now, support this mode for absolute accesses only. This mode can be use, for example, to set the device-state-change indicator and the adapter-local-summary indicator atomically. Signed-off-by: Janis Schoetterl-Glausch Reviewed-by: Thomas Huth --- include/uapi/linux/kvm.h | 7 +++ arch/s390/kvm/gaccess.h | 3 ++ arch/s390/kvm/gaccess.c | 102 +++++++++++++++++++++++++++++++++++++++ arch/s390/kvm/kvm-s390.c | 39 ++++++++++++++- 4 files changed, 149 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 0d5d4419139a..f106db1af5ee 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -588,6 +588,8 @@ struct kvm_s390_mem_op { struct { __u8 ar; /* the access register number */ __u8 key; /* access key, ignored if flag unset */ + __u8 pad1[6]; /* ignored */ + __u64 old_addr; /* ignored if flag unset */ }; __u32 sida_offset; /* offset into the sida */ __u8 reserved[32]; /* ignored */ @@ -604,6 +606,11 @@ struct kvm_s390_mem_op { #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) +#define KVM_S390_MEMOP_F_CMPXCHG (1ULL << 3) +/* flags specifying extension support */ +#define KVM_S390_MEMOP_EXTENSION_CAP_CMPXCHG 0x2 +/* Non program exception return codes (pgm codes are 16 bit) */ +#define KVM_S390_MEMOP_R_NO_XCHG (1 << 16) /* for KVM_INTERRUPT */ struct kvm_interrupt { diff --git a/arch/s390/kvm/gaccess.h b/arch/s390/kvm/gaccess.h index 9408d6cc8e2c..92a3b9fb31ec 100644 --- a/arch/s390/kvm/gaccess.h +++ b/arch/s390/kvm/gaccess.h @@ -206,6 +206,9 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra, void *data, unsigned long len, enum gacc_mode mode); +int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len, + __uint128_t *old, __uint128_t new, u8 access_key); + /** * write_guest_with_key - copy data from kernel space to guest space * @vcpu: virtual cpu diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c index 0243b6e38d36..6165e761a637 100644 --- a/arch/s390/kvm/gaccess.c +++ b/arch/s390/kvm/gaccess.c @@ -1161,6 +1161,108 @@ int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra, return rc; } +/** + * cmpxchg_guest_abs_with_key() - Perform cmpxchg on guest absolute address. + * @kvm: Virtual machine instance. + * @gpa: Absolute guest address of the location to be changed. + * @len: Operand length of the cmpxchg, required: 1 <= len <= 16. Providing a + * non power of two will result in failure. + * @old_addr: Pointer to old value. If the location at @gpa contains this value, the + * exchange will succeed. After calling cmpxchg_guest_abs_with_key() *@old + * contains the value at @gpa before the attempt to exchange the value. + * @new: The value to place at @gpa. + * @access_key: The access key to use for the guest access. + * + * Atomically exchange the value at @gpa by @new, if it contains *@old. + * Honors storage keys. + * + * Return: * 0: successful exchange + * * 1: exchange unsuccessful + * * a program interruption code indicating the reason cmpxchg could + * not be attempted + * * -EINVAL: address misaligned or len not power of two + * * -EAGAIN: transient failure (len 1 or 2) + * * -EOPNOTSUPP: read-only memslot (should never occur) + */ +int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len, + __uint128_t *old_addr, __uint128_t new, + u8 access_key) +{ + gfn_t gfn = gpa >> PAGE_SHIFT; + struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn); + bool writable; + hva_t hva; + int ret; + + if (!IS_ALIGNED(gpa, len)) + return -EINVAL; + + hva = gfn_to_hva_memslot_prot(slot, gfn, &writable); + if (kvm_is_error_hva(hva)) + return PGM_ADDRESSING; + /* + * Check if it's a read-only memslot, even though that cannot occur + * since those are unsupported. + * Don't try to actually handle that case. + */ + if (!writable) + return -EOPNOTSUPP; + + hva += offset_in_page(gpa); + switch (len) { + case 1: { + u8 old; + + ret = cmpxchg_user_key((u8 *)hva, &old, *old_addr, new, access_key); + ret = ret < 0 ? ret : old != *old_addr; + *old_addr = old; + break; + } + case 2: { + u16 old; + + ret = cmpxchg_user_key((u16 *)hva, &old, *old_addr, new, access_key); + ret = ret < 0 ? ret : old != *old_addr; + *old_addr = old; + break; + } + case 4: { + u32 old; + + ret = cmpxchg_user_key((u32 *)hva, &old, *old_addr, new, access_key); + ret = ret < 0 ? ret : old != *old_addr; + *old_addr = old; + break; + } + case 8: { + u64 old; + + ret = cmpxchg_user_key((u64 *)hva, &old, *old_addr, new, access_key); + ret = ret < 0 ? ret : old != *old_addr; + *old_addr = old; + break; + } + case 16: { + __uint128_t old; + + ret = cmpxchg_user_key((__uint128_t *)hva, &old, *old_addr, new, access_key); + ret = ret < 0 ? ret : old != *old_addr; + *old_addr = old; + break; + } + default: + return -EINVAL; + } + mark_page_dirty_in_slot(kvm, slot, gfn); + /* + * Assume that the fault is caused by protection, either key protection + * or user page write protection. + */ + if (ret == -EFAULT) + ret = PGM_PROTECTION; + return ret; +} + /** * guest_translate_address_with_key - translate guest logical into guest absolute address * @vcpu: virtual cpu diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 45d4b8182b07..47bcf2cb4345 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -576,7 +576,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_S390_VCPU_RESETS: case KVM_CAP_SET_GUEST_DEBUG: case KVM_CAP_S390_DIAG318: - case KVM_CAP_S390_MEM_OP_EXTENSION: r = 1; break; case KVM_CAP_SET_GUEST_DEBUG2: @@ -590,6 +589,14 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_S390_MEM_OP: r = MEM_OP_MAX_SIZE; break; + case KVM_CAP_S390_MEM_OP_EXTENSION: + /* + * Flag bits indicating which extensions are supported. + * The first extension doesn't use a flag, but pretend it does, + * this way that can be changed in the future. + */ + r = KVM_S390_MEMOP_EXTENSION_CAP_CMPXCHG | 1; + break; case KVM_CAP_NR_VCPUS: case KVM_CAP_MAX_VCPUS: case KVM_CAP_MAX_VCPU_ID: @@ -2714,12 +2721,19 @@ static bool access_key_invalid(u8 access_key) static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop) { void __user *uaddr = (void __user *)mop->buf; + void __user *old_addr = (void __user *)mop->old_addr; + union { + __uint128_t quad; + char raw[sizeof(__uint128_t)]; + } old = { .quad = 0}, new = { .quad = 0 }; + unsigned int off_in_quad = sizeof(new) - mop->size; u64 supported_flags; void *tmpbuf = NULL; int r, srcu_idx; supported_flags = KVM_S390_MEMOP_F_SKEY_PROTECTION - | KVM_S390_MEMOP_F_CHECK_ONLY; + | KVM_S390_MEMOP_F_CHECK_ONLY + | KVM_S390_MEMOP_F_CMPXCHG; if (mop->flags & ~supported_flags || !mop->size) return -EINVAL; if (mop->size > MEM_OP_MAX_SIZE) @@ -2741,6 +2755,19 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop) } else { mop->key = 0; } + if (mop->flags & KVM_S390_MEMOP_F_CMPXCHG) { + /* + * This validates off_in_quad. Checking that size is a power + * of two is not necessary, as cmpxchg_guest_abs_with_key + * takes care of that + */ + if (mop->size > sizeof(new)) + return -EINVAL; + if (copy_from_user(&new.raw[off_in_quad], uaddr, mop->size)) + return -EFAULT; + if (copy_from_user(&old.raw[off_in_quad], old_addr, mop->size)) + return -EFAULT; + } if (!(mop->flags & KVM_S390_MEMOP_F_CHECK_ONLY)) { tmpbuf = vmalloc(mop->size); if (!tmpbuf) @@ -2771,6 +2798,14 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop) 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, mop->key); + } else if (mop->flags & KVM_S390_MEMOP_F_CMPXCHG) { + r = cmpxchg_guest_abs_with_key(kvm, mop->gaddr, mop->size, + &old.quad, new.quad, mop->key); + if (r == 1) { + r = KVM_S390_MEMOP_R_NO_XCHG; + if (copy_to_user(old_addr, &old.raw[off_in_quad], mop->size)) + r = -EFAULT; + } } else { if (copy_from_user(tmpbuf, uaddr, mop->size)) { r = -EFAULT;