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| author | Christian Borntraeger <borntraeger@de.ibm.com> | 2017-11-21 16:02:52 +0100 |
|---|---|---|
| committer | Christian Borntraeger <borntraeger@de.ibm.com> | 2017-12-06 09:18:43 +0100 |
| commit | bb64da9aba89765fee74b395967b18a7d6c364e9 (patch) | |
| tree | c3499d7eaece67a6be01d01490c78b7ffe875e89 /Documentation | |
| parent | 940f89a5a37789b94f332755767c556a64b004e4 (diff) | |
| download | linux-bb64da9aba89765fee74b395967b18a7d6c364e9.tar.bz2 | |
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.txt | 15 |
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 |