[41/56] KVM: Clarify KVM_{SET, GET}_ONE_REG error code documentation

Commit Message

Marc Zyngier May 3, 2019, 12:44 p.m. UTC

From: Dave Martin <[e-mail]>

The current error code documentation for KVM_GET_ONE_REG and
KVM_SET_ONE_REG could be read as implying that all architectures
implement these error codes, or that KVM guarantees which error
code is returned in a particular situation.

Because this is not really the case, this patch waters down the
documentation explicitly to remove such guarantees.

EPERM is marked as arm64-specific, since for now arm64 really is
the only architecture that yields this error code for the
finalization-required case.  Keeping this as a distinct error code
is useful however for debugging due to the statefulness of the API
in this instance.

No functional change.

Suggested-by: Andrew Jones <[e-mail]>
Fixes: 395f562f2b4c ("KVM: Document errors for KVM_GET_ONE_REG and KVM_SET_ONE_REG")
Fixes: 50036ad06b7f ("KVM: arm64/sve: Document KVM API extensions for SVE")
Signed-off-by: Dave Martin <[e-mail]>
Reviewed-by: Andrew Jones <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
---
 Documentation/virtual/kvm/api.txt | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

Patch

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 5519df0d3ed0..818ac97fdabc 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1873,8 +1873,10 @@  Parameters: struct kvm_one_reg (in)
 Returns: 0 on success, negative value on failure
 Errors:
   ENOENT:   no such register
-  EPERM:    register access forbidden for architecture-dependent reasons
-  EINVAL:   other errors, such as bad size encoding for a known register
+  EINVAL:   invalid register ID, or no such register
+  EPERM:    (arm64) register access not allowed before vcpu finalization
+(These error codes are indicative only: do not rely on a specific error
+code being returned in a specific situation.)
 
 struct kvm_one_reg {
        __u64 id;
@@ -2260,10 +2262,12 @@  Architectures: all
 Type: vcpu ioctl
 Parameters: struct kvm_one_reg (in and out)
 Returns: 0 on success, negative value on failure
-Errors:
+Errors include:
   ENOENT:   no such register
-  EPERM:    register access forbidden for architecture-dependent reasons
-  EINVAL:   other errors, such as bad size encoding for a known register
+  EINVAL:   invalid register ID, or no such register
+  EPERM:    (arm64) register access not allowed before vcpu finalization
+(These error codes are indicative only: do not rely on a specific error
+code being returned in a specific situation.)
 
 This ioctl allows to receive the value of a single register implemented
 in a vcpu. The register to read is indicated by the "id" field of the