On Mon, Feb 06, 2017 at 02:25:59PM +0100, Paolo Bonzini wrote: > > > On 06/02/2017 11:46, James Hogan wrote: > > Documentation/virtual/kvm/api.txt seems to suggest that > > KVM_EXIT_HYPERCALL is obsolete. When it suggests using KVM_EXIT_MMIO, > > does it simply mean the guest should use MMIO to some virtio device of > > some sort rather than using hypercalls, or that the hypercall should > > somehow be munged into the mmio exit information? > > The former.
Okay, thanks. > > But there are cases when using hypercalls is unavoidable. In that case > the trend is to use other exit reasons than KVM_EXIT_HYPERCALL, such as > KVM_EXIT_PAPR_HCALL in PowerPC. Feel free to add KVM_EXIT_MIPS_CONOUT > or something like that. Okay, that sounds sensible. The existing mips_paravirt_defconfig does contain CONFIG_VIRTIO_CONSOLE=y though, so I'm thinking we may be able to get away without this hypercall and without old paravirt guest kernels becoming unusable. David/Andreas: would you agree, or do you feel strongly that this hypercall API should be kept? (with a different KVM exit reason) > > How would you find the character device to write to in QEMU? I imagine it'd need a custom character device driver in QEMU so it could be wired up to stdio/pty or whatever using QEMU arguments. I've only tested it with a test case in my own MIPS KVM test suite so far though. Cheers James
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