[PATCH v5 00/10] KVM: s390: Extend MEM_OP ioctl by storage key checked cmpxchg

[Janis Schoetterl-Glausch <scgl@linux.ibm.com>]

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
-- 
2.34.1