KVM: x86: clear vcpu->run->hypercall.ret before exiting for KVM_EXIT_HYPERCALL

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QEMU up to 9.2.0 is assuming that vcpu->run->hypercall.ret is 0 on exit and
it never modifies it when processing KVM_EXIT_HYPERCALL.  Make this explicit
in the code, to avoid breakage when KVM starts modifying that field.

This in principle is not a good idea... It would have been much better if
KVM had set the field to -KVM_ENOSYS from the beginning, so that a dumb
userspace that does nothing on KVM_EXIT_HYPERCALL would tell the guest it
does not support KVM_HC_MAP_GPA_RANGE.  However, breaking userspace is
a Very Bad Thing, as everybody should know.

Reported-by: Binbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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This commit is contained in:

Paolo Bonzini 2024-12-13 14:36:25 -05:00

parent 10b2c8a67c

commit 9a1dfeff44

2 changed files with 21 additions and 0 deletions

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14

arch/x86/kvm/svm/sev.c

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7

arch/x86/kvm/x86.c

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