Re: [PATCHv2 23/29] x86/tdx: Add helper to convert memory between shared and private

[Borislav Petkov]

On Mon, Jan 24, 2022 at 06:02:09PM +0300, Kirill A. Shutemov wrote:
> +static bool tdx_accept_page(phys_addr_t gpa, enum pg_level pg_level)

accept_page() as it is a static function.

> +int tdx_hcall_request_gpa_type(phys_addr_t start, phys_addr_t end, bool enc)
> +{
> +	u64 ret;
> +
> +	if (end <= start)
> +		return -EINVAL;
> +
> +	if (!enc) {
> +		start |= tdx_shared_mask();
> +		end |= tdx_shared_mask();
> +	}
> +
> +	/*
> +	 * Notify the VMM about page mapping conversion. More info about ABI
> +	 * can be found in TDX Guest-Host-Communication Interface (GHCI),
> +	 * sec "TDG.VP.VMCALL<MapGPA>"
> +	 */
> +	ret = _tdx_hypercall(TDVMCALL_MAP_GPA, start, end - start, 0, 0, NULL);
> +


^ Superfluous newline.

> +	if (ret)
> +		ret = -EIO;
> +
> +	if (ret || !enc)

Is the second case here after the "||" the conversion-to-shared where it
only needs to notify with MapGPA and return?

Of all the places, this one needs a comment.

> +		return ret;
> +
> +	/*
> +	 * For shared->private conversion, accept the page using
> +	 * TDX_ACCEPT_PAGE TDX module call.
> +	 */
> +	while (start < end) {
> +		/* Try 2M page accept first if possible */
> +		if (!(start & ~PMD_MASK) && end - start >= PMD_SIZE &&
> +		    !tdx_accept_page(start, PG_LEVEL_2M)) {

What happens here if the module doesn't accept the page? No error
reporting, no error handling, no warning, nada?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette