Re: [PATCHv2 08/29] x86/tdx: Handle in-kernel MMIO

Dave Hansen
2022-01-24T23:37:19Z

> +static bool tdx_mmio(int size, bool write, unsigned long addr,
> + unsigned long *val)
> +{
> + struct tdx_hypercall_output out;
> + u64 err;
> +
> + err = _tdx_hypercall(EXIT_REASON_EPT_VIOLATION, size, write,
> + addr, *val, &out);
> + if (err)
> + return true;
> +
> + *val = out.r11;
> + return false;
> +}
> +
> +static bool tdx_mmio_read(int size, unsigned long addr, unsigned long *val)
> +{
> + return tdx_mmio(size, false, addr, val);
> +}
> +
> +static bool tdx_mmio_write(int size, unsigned long addr, unsigned long *val)
> +{
> + return tdx_mmio(size, true, addr, val);
> +}
> +
> +static int tdx_handle_mmio(struct pt_regs *regs, struct ve_info *ve)
> +{
...
> + bool err;

I'll agree with Josh on one point: "bool err" _is_ weird.

Things tend to either return int with 0 for success or bool with true
for success.

The tdx_handle*() ones seem OK to me. It's pretty normal to have a
literal "handler" return true if things were handled.

I'd probably just make tdx_mmio() return an int. It seems to only able
to return -EFAULT anyway, so changing the return from bool->int and doing:

- return false;
+ return -EFAULT;

isn't exactly a heavy lift.