Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
KVM: arm64: Add documentation for KVM_EXIT_ARM_LDST64B
Add a bit of documentation for KVM_EXIT_ARM_LDST64B so that userspace
knows what to expect.
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Oliver Upton <oupton@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com>
Signed-off-by: Will Deacon <will@kernel.org>
authored by
Marc Zyngier
and committed by
Will Deacon
902eebac
f174a9ff
+36
-7
+36
-7
Documentation/virt/kvm/api.rst
+36
-7
Documentation/virt/kvm/api.rst
···
1303
1303
information or because there is no device mapped at the accessed IPA, then
1304
1304
userspace can ask the kernel to inject an external abort using the address
1305
1305
from the exiting fault on the VCPU. It is a programming error to set
1306
-
ext_dabt_pending after an exit which was not either KVM_EXIT_MMIO or
1307
-
KVM_EXIT_ARM_NISV. This feature is only available if the system supports
1308
-
KVM_CAP_ARM_INJECT_EXT_DABT. This is a helper which provides commonality in
1309
-
how userspace reports accesses for the above cases to guests, across different
1310
-
userspace implementations. Nevertheless, userspace can still emulate all Arm
1311
-
exceptions by manipulating individual registers using the KVM_SET_ONE_REG API.
1306
+
ext_dabt_pending after an exit which was not either KVM_EXIT_MMIO,
1307
+
KVM_EXIT_ARM_NISV, or KVM_EXIT_ARM_LDST64B. This feature is only available if
1308
+
the system supports KVM_CAP_ARM_INJECT_EXT_DABT. This is a helper which
1309
+
provides commonality in how userspace reports accesses for the above cases to
1310
+
guests, across different userspace implementations. Nevertheless, userspace
1311
+
can still emulate all Arm exceptions by manipulating individual registers
1312
+
using the KVM_SET_ONE_REG API.
1312
1313
1313
1314
See KVM_GET_VCPU_EVENTS for the data structure.
1314
1315
···
7051
7050
7052
7051
::
7053
7052
7054
-
/* KVM_EXIT_ARM_NISV */
7053
+
/* KVM_EXIT_ARM_NISV / KVM_EXIT_ARM_LDST64B */
7055
7054
struct {
7056
7055
__u64 esr_iss;
7057
7056
__u64 fault_ipa;
7058
7057
} arm_nisv;
7058
+
7059
+
- KVM_EXIT_ARM_NISV:
7059
7060
7060
7061
Used on arm64 systems. If a guest accesses memory not in a memslot,
7061
7062
KVM will typically return to userspace and ask it to do MMIO emulation on its
···
7091
7088
Note that although KVM_CAP_ARM_NISV_TO_USER will be reported if
7092
7089
queried outside of a protected VM context, the feature will not be
7093
7090
exposed if queried on a protected VM file descriptor.
7091
+
7092
+
- KVM_EXIT_ARM_LDST64B:
7093
+
7094
+
Used on arm64 systems. When a guest using a LD64B, ST64B, ST64BV, ST64BV0,
7095
+
outside of a memslot, KVM will return to userspace with KVM_EXIT_ARM_LDST64B,
7096
+
exposing the relevant ESR_EL2 information and faulting IPA, similarly to
7097
+
KVM_EXIT_ARM_NISV.
7098
+
7099
+
Userspace is supposed to fully emulate the instructions, which includes:
7100
+
7101
+
- fetch of the operands for a store, including ACCDATA_EL1 in the case
7102
+
of a ST64BV0 instruction
7103
+
- deal with the endianness if the guest is big-endian
7104
+
- emulate the access, including the delivery of an exception if the
7105
+
access didn't succeed
7106
+
- provide a return value in the case of ST64BV/ST64BV0
7107
+
- return the data in the case of a load
7108
+
- increment PC if the instruction was successfully executed
7109
+
7110
+
Note that there is no expectation of performance for this emulation, as it
7111
+
involves a large number of interaction with the guest state. It is, however,
7112
+
expected that the instruction's semantics are preserved, specially the
7113
+
single-copy atomicity property of the 64 byte access.
7114
+
7115
+
This exit reason must be handled if userspace sets ID_AA64ISAR1_EL1.LS64 to a
7116
+
non-zero value, indicating that FEAT_LS64* is enabled.
7094
7117
7095
7118
::
7096
7119