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.
Also contains some fixes/changes for the memop selftest independent of the cmpxchg changes.
v4 -> v5 * refuse cmpxchg if not write (thanks Thomas) * minor doc changes (thanks Claudio) * picked up R-b's (thanks Thomas & Claudio) * memop selftest fixes * rebased
v3 -> v4 * no functional change intended * rework documentation a bit * name extension cap cmpxchg bit * picked up R-b (thanks Thomas) * various changes (rename variable, comments, ...) see range-diff below
v2 -> v3 * rebase onto the wip/cmpxchg_user_key branch in the s390 kernel repo * use __uint128_t instead of unsigned __int128 * put moving of testlist into main into separate patch * pick up R-b's (thanks Nico)
v1 -> v2 * get rid of xrk instruction for cmpxchg byte and short implementation * pass old parameter via pointer instead of in mem_op struct * indicate failure of cmpxchg due to wrong old value by special return code * picked up R-b's (thanks Thomas)
Janis Schoetterl-Glausch (10): KVM: s390: Extend MEM_OP ioctl by storage key checked cmpxchg Documentation: KVM: s390: Describe KVM_S390_MEMOP_F_CMPXCHG KVM: s390: selftest: memop: Pass mop_desc via pointer KVM: s390: selftest: memop: Replace macros by functions KVM: s390: selftest: memop: Move testlist into main KVM: s390: selftest: memop: Add cmpxchg tests KVM: s390: selftest: memop: Add bad address test KVM: s390: selftest: memop: Fix typo KVM: s390: selftest: memop: Fix wrong address being used in test KVM: s390: selftest: memop: Fix integer literal
Documentation/virt/kvm/api.rst | 20 +- include/uapi/linux/kvm.h | 7 + arch/s390/kvm/gaccess.h | 3 + arch/s390/kvm/gaccess.c | 102 ++++ arch/s390/kvm/kvm-s390.c | 41 +- tools/testing/selftests/kvm/s390x/memop.c | 675 +++++++++++++++++----- 6 files changed, 696 insertions(+), 152 deletions(-)
Range-diff against v4: 1: 75a20d2e27f2 ! 1: 6adc166ee141 KVM: s390: Extend MEM_OP ioctl by storage key checked cmpxchg @@ arch/s390/kvm/kvm-s390.c: static int kvm_s390_vm_mem_op(struct kvm *kvm, struct + */ + if (mop->size > sizeof(new)) + return -EINVAL; ++ if (mop->op != KVM_S390_MEMOP_ABSOLUTE_WRITE) ++ 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)) 2: 5c5ad96a4c81 ! 2: fce9a063ab70 Documentation: KVM: s390: Describe KVM_S390_MEMOP_F_CMPXCHG @@ Commit message checked) cmpxchg operations on guest memory.
Signed-off-by: Janis Schoetterl-Glausch scgl@linux.ibm.com + Reviewed-by: Claudio Imbrenda imbrenda@linux.ibm.com
## Documentation/virt/kvm/api.rst ## @@ Documentation/virt/kvm/api.rst: The fields in each entry are defined as follows: @@ Documentation/virt/kvm/api.rst: The fields in each entry are defined as follows: :Returns: = 0 on success, < 0 on generic error (e.g. -EFAULT or -ENOMEM), - > 0 if an exception occurred while walking the page tables -+ 16 bit program exception code if the access causes such an exception -+ other code > 0xffff with special meaning ++ 16 bit program exception code if the access causes such an exception, ++ other code > 0xffff with special meaning.
Read or write data from/to the VM's memory. The KVM_CAP_S390_MEM_OP_EXTENSION capability specifies what functionality is 3: 9cbcb313d91d = 3: 94c1165ae24a KVM: s390: selftest: memop: Pass mop_desc via pointer 4: 21d98b9deaae ! 4: 027c87eee0ac KVM: s390: selftest: memop: Replace macros by functions @@ Commit message need the exta flexibility.
Signed-off-by: Janis Schoetterl-Glausch scgl@linux.ibm.com + Reviewed-by: Thomas Huth thuth@redhat.com
## tools/testing/selftests/kvm/s390x/memop.c ## @@ tools/testing/selftests/kvm/s390x/memop.c: struct mop_desc { 5: 866fcd7fbc97 ! 5: 16ac410ecc0f KVM: s390: selftest: memop: Move testlist into main @@ tools/testing/selftests/kvm/s390x/memop.c: static void test_errors(void) { int extension_cap, idx;
-+ setbuf(stdout, NULL); /* Tell stdout not to buffer its content */ TEST_REQUIRE(kvm_has_cap(KVM_CAP_S390_MEM_OP)); + extension_cap = kvm_check_cap(KVM_CAP_S390_MEM_OP_EXTENSION);
-- setbuf(stdout, NULL); /* Tell stdout not to buffer its content */ +- ksft_print_header(); + struct testdef { + const char *name; + void (*test)(void); @@ tools/testing/selftests/kvm/s390x/memop.c: static void test_errors(void) + }, + };
- ksft_print_header(); -- ++ ksft_print_header(); ksft_set_plan(ARRAY_SIZE(testlist));
- extension_cap = kvm_check_cap(KVM_CAP_S390_MEM_OP_EXTENSION); @@ tools/testing/selftests/kvm/s390x/memop.c: static void test_errors(void) - ksft_test_result_skip("%s - extension level %d not supported\n", - testlist[idx].name, - testlist[idx].extension); -+ ksft_test_result_skip("%s - requirements not met (kernel has extension cap %#x\n)", ++ ksft_test_result_skip("%s - requirements not met (kernel has extension cap %#x)\n", + testlist[idx].name, extension_cap); } } 6: c3e473677786 ! 6: 214281b6eb96 KVM: s390: selftest: memop: Add cmpxchg tests @@ tools/testing/selftests/kvm/s390x/memop.c: static void test_errors(void) + rv = ERR_MOP(t.vm, ABSOLUTE, WRITE, mem1, i, GADDR((void *)~0xfffUL), + CMPXCHG_OLD(&old)); + TEST_ASSERT(rv > 0, "ioctl allows bad guest address for cmpxchg"); ++ rv = ERR_MOP(t.vm, ABSOLUTE, READ, mem1, i, GADDR_V(mem1), ++ CMPXCHG_OLD(&old)); ++ TEST_ASSERT(rv == -1 && errno == EINVAL, ++ "ioctl allows read cmpxchg call"); + } + for (i = 2; i <= 16; i *= 2) { + rv = ERR_MOP(t.vm, ABSOLUTE, WRITE, mem1, i, GADDR_V(mem1 + 1), 7: 90288760656e = 7: 2d6776733e64 KVM: s390: selftest: memop: Add bad address test 8: e3d4b9b2ba61 = 8: 8c49eafd2881 KVM: s390: selftest: memop: Fix typo 9: 13fedd6e3d9e = 9: 0af907110b34 KVM: s390: selftest: memop: Fix wrong address being used in test -: ------------ > 10: 886c80b2bdce KVM: s390: selftest: memop: Fix integer literal