On Tue, Nov 07, 2023 at 05:31:42PM +0100, Borislav Petkov wrote:
> On Mon, Oct 16, 2023 at 08:27:35AM -0500, Michael Roth wrote:
> > +static bool early_rmptable_check(void)
> > +{
> > + u64 rmp_base, rmp_size;
> > +
> > + /*
> > + * For early BSP initialization, max_pfn won't be set up yet, wait until
> > + * it is set before performing the RMP table calculations.
> > + */
> > + if (!max_pfn)
> > + return true;
>
> This already says that this is called at the wrong point during init.
>
> Right now we have
>
> early_identify_cpu -> early_init_amd -> early_detect_mem_encrypt
>
> which runs only on the BSP but then early_init_amd() is called in
> init_amd() too so that it takes care of the APs too.
>
> Which ends up doing a lot of unnecessary work on each AP in
> early_detect_mem_encrypt() like calculating the RMP size on each AP
> unnecessarily where this needs to happen exactly once.
>
> Is there any reason why this function cannot be moved to init_amd()
> where it'll do the normal, per-AP init?
>
> And the stuff that needs to happen once, needs to be called once too.
I've renamed/repurposed snp_get_rmptable_info() to
snp_probe_rmptable_info(). It now reads the MSRs, sanity-checks them,
and stores the values into ro_after_init variables on success.
Subsequent code uses those values to initialize the RMP table mapping
instead of re-reading the MSRs.
I've moved the call-site for snp_probe_rmptable_info() to
bsp_init_amd(), which gets called right after early_init_amd(), so
should still be early enough to clear X86_FEATURE_SEV_SNP such that
AutoIBRS doesn't get disabled if SNP isn't available on the system. APs
don't call bsp_init_amd(), so that should avoid doing multiple MSR reads.
And I think Ashish has all the other review comments addressed now.
Thanks,
Mike
