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>
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@ -2901,14 +2901,19 @@ userspace buffer and its length:
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struct kvm_s390_irq_state {
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__u64 buf;
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__u32 flags;
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__u32 flags; /* will stay unused for compatibility reasons */
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__u32 len;
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__u32 reserved[4];
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__u32 reserved[4]; /* will stay unused for compatibility reasons */
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};
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Userspace passes in the above struct and for each pending interrupt a
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struct kvm_s390_irq is copied to the provided buffer.
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The structure contains a flags and a reserved field for future extensions. As
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the kernel never checked for flags == 0 and QEMU never pre-zeroed flags and
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reserved, these fields can not be used in the future without breaking
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compatibility.
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If -ENOBUFS is returned the buffer provided was too small and userspace
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may retry with a bigger buffer.
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@ -2932,10 +2937,14 @@ containing a struct kvm_s390_irq_state:
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struct kvm_s390_irq_state {
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__u64 buf;
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__u32 flags; /* will stay unused for compatibility reasons */
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__u32 len;
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__u32 pad;
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__u32 reserved[4]; /* will stay unused for compatibility reasons */
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};
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The restrictions for flags and reserved apply as well.
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(see KVM_S390_GET_IRQ_STATE)
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The userspace memory referenced by buf contains a struct kvm_s390_irq
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for each interrupt to be injected into the guest.
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If one of the interrupts could not be injected for some reason the
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@ -1,8 +1,8 @@
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// SPDX-License-Identifier: GPL-2.0
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/*
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* hosting zSeries kernel virtual machines
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* hosting IBM Z kernel virtual machines (s390x)
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*
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* Copyright IBM Corp. 2008, 2009
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* Copyright IBM Corp. 2008, 2017
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*
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* Author(s): Carsten Otte <cotte@de.ibm.com>
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* Christian Borntraeger <borntraeger@de.ibm.com>
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@ -3808,6 +3808,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
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r = -EINVAL;
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break;
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}
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/* do not use irq_state.flags, it will break old QEMUs */
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r = kvm_s390_set_irq_state(vcpu,
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(void __user *) irq_state.buf,
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irq_state.len);
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@ -3823,6 +3824,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
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r = -EINVAL;
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break;
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}
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/* do not use irq_state.flags, it will break old QEMUs */
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r = kvm_s390_get_irq_state(vcpu,
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(__u8 __user *) irq_state.buf,
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irq_state.len);
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@ -630,9 +630,9 @@ struct kvm_s390_irq {
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struct kvm_s390_irq_state {
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__u64 buf;
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__u32 flags;
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__u32 flags; /* will stay unused for compatibility reasons */
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__u32 len;
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__u32 reserved[4];
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__u32 reserved[4]; /* will stay unused for compatibility reasons */
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};
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/* for KVM_SET_GUEST_DEBUG */
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