Re: [PATCH v19 030/130] KVM: TDX: Add helper functions to print TDX SEAMCALL error

Isaku Yamahata
2024-03-21T23:52:15Z

On Thu, Mar 21, 2024 at 12:09:57PM +1300,
"Huang, Kai" <kai.huang@intel.com> wrote:

> > Does it make sense?
> >
> > void pr_tdx_error(u64 op, u64 error_code)
> > {
> > pr_err_ratelimited("SEAMCALL (0x%016llx) failed: 0x%016llx\n",
> > op, error_code);
> > }
>
> Should we also have a _ret version?
>
> void pr_seamcall_err(u64 op, u64 err)
> {
> /* A comment to explain why using the _ratelimited() version? */

Because KVM can hit successive seamcall erorrs e.g. during desutructing TD,
(it's unintentional sometimes), ratelimited version is preferred as safe guard.
For example, SEAMCALL on all or some LPs (TDH_MNG_KEY_FREEID) can fail at the
same time. And the number of LPs can be hundreds.

> pr_err_ratelimited(...);
> }
>
> void pr_seamcall_err_ret(u64 op, u64 err, struct tdx_module_args *arg)
> {
> pr_err_seamcall(op, err);
>
> pr_err_ratelimited(...);
> }
>
> (Hmm... if you look at the tdx.c in TDX host, there's similar code there,
> and again, it was a little bit annoying when I did that..)
>
> Again, if we just use seamcall_ret() for ALL SEAMCALLs except VP.ENTER, we
> can simply have one..

What about this?

void pr_seamcall_err_ret(u64 op, u64 err, struct tdx_module_args *arg)
{
pr_err_ratelimited("SEAMCALL (0x%016llx) failed: 0x%016llx\n",
op, error_code);
if (arg)
pr_err_ratelimited(...);
}

> > void pr_tdx_sept_error(u64 op, u64 error_code, const union tdx_sept_entry *entry,
> > const union tdx_sept_level_state *level_state)
> > {
> > #define MSG \
> > "SEAMCALL (0x%016llx) failed: 0x%016llx entry 0x%016llx level_state 0x%016llx\n"
> > pr_err_ratelimited(MSG, op, error_code, entry->raw, level_state->raw);
> > }
>
> A higher-level wrapper to print SEPT error is fine to me, but do it in a
> separate patch.

Ok, Let's postpone custom version.
--
Isaku Yamahata <isaku.yamahata@intel.com>