On 11/13/24 12:51, Edgecombe, Rick P wrote:
> However, some future user of TDH.PHYMEM.PAGE.RECLAIM might want to do something
> else where the enums could add code clarity. But this goes down the road of
> building things that are not needed today.
Here's why the current code is a bit suboptimal:
> +/* TDH.PHYMEM.PAGE.RECLAIM is allowed only when destroying the TD. */
> +static int __tdx_reclaim_page(hpa_t pa)
> +{
...
> + for (i = TDX_SEAMCALL_RETRIES; i > 0; i--) {
> + err = tdh_phymem_page_reclaim(pa, &rcx, &rdx, &r8);
...
> +out:
> + if (WARN_ON_ONCE(err)) {
> + pr_tdx_error_3(TDH_PHYMEM_PAGE_RECLAIM, err, rcx, rdx, r8);
> + return -EIO;
> + }
> + return 0;
> +}
Let's say I see the error get spit out on the console. I can't make any
sense out of it from this spot. I need to go over to the TDX docs or
tdh_phymem_page_reclaim() to look at the *comment* to figure out what
these the registers are named.
The code as proposed has zero self-documenting properties. It's
actually completely non-self-documenting. It isn't _any_ better for
readability than just doing:
struct tdx_module_args args = {};
for (i = TDX_SEAMCALL_RETRIES; i > 0; i--) {
args.rcx = pa;
err = seamcall_ret(TDH_PHYMEM_PAGE_RECLAIM, &args);
...
}
pr_tdx_error_3(TDH_PHYMEM_PAGE_RECLAIM, err,
args.rcx, args.rdx, args.r8);
Also, this is also showing a lack of naming discipline where things are
named. The first argument is 'pa' in here but 'page' on the other side:
> +u64 tdh_phymem_page_reclaim(u64 page, u64 *rcx, u64 *rdx, u64 *r8)
> +{
> + struct tdx_module_args args = {
> + .rcx = page,
I can't tell you how many recompiles it's cost me when I got lazy about
physical addr vs. virtual addr vs. struct page vs. pfn.
So, yeah, I'd rather not export seamcall_ret(), but I'd rather do that
than have a layer of abstraction that's adding little value while it
also brings obfuscation.
