Re: [PATCHv6 04/30] x86/tdx: Extend the confidential computing API to support TDX guests

Thomas Gleixner
2022-03-17T00:02:01Z

On Wed, Mar 16 2022 at 05:08, Kirill A. Shutemov wrote:
> +
> +static void get_info(unsigned int *gpa_width)

get_info() is really not a descriptive function name. Also why does this
need a pointer and does not return gpa_width?

>
> setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
>
> + get_info(&gpa_width);
> +
> + cc_set_vendor(CC_VENDOR_INTEL);
> +
> + /*
> + * The highest bit of a guest physical address is the "sharing" bit.
> + * Set it for shared pages and clear it for private pages.
> + */
> + cc_set_mask(BIT_ULL(gpa_width - 1));

The code ordering here is silly:

1) Retrieve gpa width
2) Set CC vendor
3) Use gpa width

static u64 get_cc_mask(void)
{
gpa_width = magic();

/*
* Comment explaining the return value
*/
return BIT_ULL(gpa_width - 1);
}

and

cc_set_vendor(CC_VENDOR_INTEL);
cc_set_mask(get_cc_mask());

would be too intuitive, right?

Thanks,

tglx

---

“My tastes are simple: I am easily satisfied with the best.”
― Winston S. Churchill