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References: <20220124150215.36893-1-kirill.shutemov@linux.intel.com>
 <20220124150215.36893-9-kirill.shutemov@linux.intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
Subject: Re: [PATCHv2 08/29] x86/tdx: Handle in-kernel MMIO
In-Reply-To: <20220124150215.36893-9-kirill.shutemov@linux.intel.com>
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> +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.