On Fri, 2021-10-22 at 11:36 -0400, Paolo Bonzini wrote:
> The caller of kernel_pio already has arguments for most of what kernel_pio
> fishes out of vcpu->arch.pio. This is the first step towards ensuring that
> vcpu->arch.pio.* is only used when exiting to userspace.
>
> We can now also WARN if emulated PIO performs successful in-kernel iterations
> before having to fall back to userspace. The code is not ready for that, and
> it should never happen.
>
> No functional change intended.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 39 +++++++++++++++++----------------------
> 1 file changed, 17 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b26647a5ea22..d6b8df7cea80 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6886,37 +6886,32 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
> return emulator_write_emulated(ctxt, addr, new, bytes, exception);
> }
>
> -static int kernel_pio(struct kvm_vcpu *vcpu, void *pd)
> -{
> - int r = 0, i;
> -
> - for (i = 0; i < vcpu->arch.pio.count; i++) {
> - if (vcpu->arch.pio.in)
> - r = kvm_io_bus_read(vcpu, KVM_PIO_BUS, vcpu->arch.pio.port,
> - vcpu->arch.pio.size, pd);
> - else
> - r = kvm_io_bus_write(vcpu, KVM_PIO_BUS,
> - vcpu->arch.pio.port, vcpu->arch.pio.size,
> - pd);
> - if (r)
> - break;
> - pd += vcpu->arch.pio.size;
> - }
> - return r;
> -}
> -
> static int emulator_pio_in_out(struct kvm_vcpu *vcpu, int size,
> unsigned short port,
> unsigned int count, bool in)
> {
> + void *data = vcpu->arch.pio_data;
> + unsigned i;
> + int r;
> +
> vcpu->arch.pio.port = port;
> vcpu->arch.pio.in = in;
> - vcpu->arch.pio.count = count;
> + vcpu->arch.pio.count = count;
> vcpu->arch.pio.size = size;
>
> - if (!kernel_pio(vcpu, vcpu->arch.pio_data))
> - return 1;
> + for (i = 0; i < count; i++) {
> + if (in)
> + r = kvm_io_bus_read(vcpu, KVM_PIO_BUS, port, size, data);
> + else
> + r = kvm_io_bus_write(vcpu, KVM_PIO_BUS, port, size, data);
> + if (r)
> + goto userspace_io;
> + data += size;
> + }
> + return 1;
>
> +userspace_io:
> + WARN_ON(i != 0);
> vcpu->run->exit_reason = KVM_EXIT_IO;
> vcpu->run->io.direction = in ? KVM_EXIT_IO_IN : KVM_EXIT_IO_OUT;
> vcpu->run->io.size = size;
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Best regards,
Maxim Levitsky
