[PATCH v5 00/10] KVM: s390: Extend MEM_OP ioctl by storage key checked cmpxchg
From: Janis Schoetterl-Glausch
Date: Tue Jan 10 2023 - 15:27:58 EST
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@xxxxxxxxxxxxx>
+ Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
## 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@xxxxxxxxxxxxx>
+ Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
## 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
--
2.34.1