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

[Alexandru Elisei <alexandru.elisei@arm.com>]

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;
>  }