Re: [PATCH kvmtool 06/21] hw/i8042: Refactor trap handler

Alexandru Elisei
2021-02-11T17:25:55Z

Hi Andre,

On 12/10/20 2:28 PM, Andre Przywara wrote:
> With the planned retirement of the special ioport emulation code, we
> need to provide an emulation function compatible with the MMIO
> prototype.
>
> Adjust the trap handler to use that new function, and provide shims to
> implement the old ioport interface, for now.
>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
> hw/i8042.c | 68 +++++++++++++++++++++++++++---------------------------
> 1 file changed, 34 insertions(+), 34 deletions(-)
>
> diff --git a/hw/i8042.c b/hw/i8042.c
> index 36ee183f..eb1f9d28 100644
> --- a/hw/i8042.c
> +++ b/hw/i8042.c
> @@ -292,52 +292,52 @@ static void kbd_reset(void)
> };
> }
>
> -/*
> - * Called when the OS has written to one of the keyboard's ports (0x60 or 0x64)
> - */
> -static bool kbd_in(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size)
> +static void kbd_io(struct kvm_cpu *vcpu, u64 addr, u8 *data, u32 len,
> + u8 is_write, void *ptr)
> {
> - switch (port) {
> - case I8042_COMMAND_REG: {
> - u8 value = kbd_read_status();
> - ioport__write8(data, value);
> + u8 value;
> +
> + if (is_write)
> + value = ioport__read8(data);
> +
> + switch (addr) {
> + case I8042_COMMAND_REG:
> + if (is_write)
> + kbd_write_command(vcpu->kvm, value);
> + else
> + value = kbd_read_status();
> break;
> - }
> - case I8042_DATA_REG: {
> - u8 value = kbd_read_data();
> - ioport__write8(data, value);
> + case I8042_DATA_REG:
> + if (is_write)
> + kbd_write_data(value);
> + else
> + value = kbd_read_data();
> break;
> - }
> - case I8042_PORT_B_REG: {
> - ioport__write8(data, 0x20);
> + case I8042_PORT_B_REG:
> + if (!is_write)
> + value = 0x20;
> break;
> - }
> default:
> - return false;
> + return;

Any particular reason for removing the false return value? I don't see it
mentioned in the commit message. Otherwise this is identical to the two functions
it replaces.

> }
>
> + if (!is_write)
> + ioport__write8(data, value);
> +}
> +
> +/*
> + * Called when the OS has written to one of the keyboard's ports (0x60 or 0x64)
> + */
> +static bool kbd_in(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size)
> +{
> + kbd_io(vcpu, port, data, size, false, NULL);

is_write is an u8, not a bool.

I never could wrap my head around the ioport convention of "in" (read) and "out"
(write). To be honest, changing is_write changed to an enum so it's crystal clear
what is happening would help with that a lot, but I guess that's a separate patch.

Thanks,

Alex

> +
> return true;
> }
>
> static bool kbd_out(struct ioport *ioport, struct kvm_cpu *vcpu, u16 port, void *data, int size)
> {
> - switch (port) {
> - case I8042_COMMAND_REG: {
> - u8 value = ioport__read8(data);
> - kbd_write_command(vcpu->kvm, value);
> - break;
> - }
> - case I8042_DATA_REG: {
> - u8 value = ioport__read8(data);
> - kbd_write_data(value);
> - break;
> - }
> - case I8042_PORT_B_REG: {
> - break;
> - }
> - default:
> - return false;
> - }
> + kbd_io(vcpu, port, data, size, true, NULL);
>
> return true;
> }