Re: [PATCH kvmtool v2 06/22] hw/i8042: Refactor trap handler

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

Hi Andre,

On 2/25/21 12:58 AM, 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 7d1f9772..ab866662 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;
>  	}
>  
> +	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, 0, NULL);
> +
>  	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, 1, NULL);

I think I made a mistake when I suggested that is_write should 0 or 1. I followed
the emulation path in kvmtool and it turns out that is_write is supposed to
represent the field with the same name from the anonymous struct mmio from struct
kvm_run (more precisely, the struct defined at line 4980 from
Documentation/virt/kvm/api.rst, Linux tag v5.11). I think the is_write field is
declared in kvm_run as an u8 for compatibility with an userspace which might not
know about the bool type. is_write is also treated as a bool in the MMIO exit path
by KVM (see arch/arm64/kvm/mmio.c::io_mem_abort()).

kvmtool assigns is_write a boolean value everywhere except in this file, would you
mind changing it back to a bool? Sorry for suggesting the wrong thing.

I checked that the code remains functionally identical, with the above change:

Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>

Thanks,

Alex

>  
>  	return true;
>  }