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authorChristian Borntraeger <borntraeger@de.ibm.com>2017-11-21 18:02:52 +0300
committerChristian Borntraeger <borntraeger@de.ibm.com>2017-12-06 11:18:43 +0300
commitbb64da9aba89765fee74b395967b18a7d6c364e9 (patch)
treec3499d7eaece67a6be01d01490c78b7ffe875e89 /Documentation
parent940f89a5a37789b94f332755767c556a64b004e4 (diff)
downloadlinux-bb64da9aba89765fee74b395967b18a7d6c364e9.tar.xz
KVM: s390: mark irq_state.flags as non-usable
Old kernels did not check for zero in the irq_state.flags field and old QEMUs did not zero the flag/reserved fields when calling KVM_S390_*_IRQ_STATE. Let's add comments to prevent future uses of these fields. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Reviewed-by: Thomas Huth <thuth@redhat.com> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Reviewed-by: David Hildenbrand <david@redhat.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/virtual/kvm/api.txt15
1 files changed, 12 insertions, 3 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index f670e4b9e7f3..57d3ee9e4bde 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2901,14 +2901,19 @@ userspace buffer and its length:
struct kvm_s390_irq_state {
__u64 buf;
- __u32 flags;
+ __u32 flags; /* will stay unused for compatibility reasons */
__u32 len;
- __u32 reserved[4];
+ __u32 reserved[4]; /* will stay unused for compatibility reasons */
};
Userspace passes in the above struct and for each pending interrupt a
struct kvm_s390_irq is copied to the provided buffer.
+The structure contains a flags and a reserved field for future extensions. As
+the kernel never checked for flags == 0 and QEMU never pre-zeroed flags and
+reserved, these fields can not be used in the future without breaking
+compatibility.
+
If -ENOBUFS is returned the buffer provided was too small and userspace
may retry with a bigger buffer.
@@ -2932,10 +2937,14 @@ containing a struct kvm_s390_irq_state:
struct kvm_s390_irq_state {
__u64 buf;
+ __u32 flags; /* will stay unused for compatibility reasons */
__u32 len;
- __u32 pad;
+ __u32 reserved[4]; /* will stay unused for compatibility reasons */
};
+The restrictions for flags and reserved apply as well.
+(see KVM_S390_GET_IRQ_STATE)
+
The userspace memory referenced by buf contains a struct kvm_s390_irq
for each interrupt to be injected into the guest.
If one of the interrupts could not be injected for some reason the