Re: [PATCH] x86/sev: Apply RMP table fixups for kexec.

[Kalra, Ashish]

On 4/2/2024 5:09 PM, Tom Lendacky wrote:
> On 3/12/24 13:47, Ashish Kalra wrote:
> > From: Ashish Kalra <ashish.kalra@xxxxxxx>
> >
> > RMP table start and end physical range may not be aligned to 2MB in
> > the e820 tables causing fatal RMP page faults during kexec boot when
> > new page allocations are done in the same 2MB page as the RMP table.
> > Check if RMP table start and end physical range in e820_table is not
> > aligned to 2MB and in that case use e820__range_update() to map this
> > range to reserved.
> >
> > Override e820__memory_setup_default() to check and apply these RMP table
> > fixups in e820_table before e820_table is used to setup
> > e280_table_firmware and e820_table_kexec.
> >
> > Fixes: c3b86e61b756 ("x86/cpufeatures: Enable/unmask SEV-SNP CPU 
> > feature")
> > Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
> > ---
> >   arch/x86/virt/svm/sev.c | 52 +++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 52 insertions(+)
> >
> > diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> > index cffe1157a90a..e0d7584df28f 100644
> > --- a/arch/x86/virt/svm/sev.c
> > +++ b/arch/x86/virt/svm/sev.c
> > @@ -65,6 +65,8 @@ static u64 probed_rmp_base, probed_rmp_size;
> >   static struct rmpentry *rmptable __ro_after_init;
> >   static u64 rmptable_max_pfn __ro_after_init;
> >   +static char *__init snp_rmptable_e820_fixup(void);
> > +
> >   static LIST_HEAD(snp_leaked_pages_list);
> >   static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);
> >   @@ -160,9 +162,59 @@ bool snp_probe_rmptable_info(void)
> >       pr_info("RMP table physical range [0x%016llx - 0x%016llx]\n",
> >           probed_rmp_base, probed_rmp_base + probed_rmp_size - 1);
> >   +    /*
> > +     * Override e820__memory_setup_default() to do any RMP table fixups
> > +     * for kexec if required.
> > +     */
> > +    x86_init.resources.memory_setup = snp_rmptable_e820_fixup;
>
> This produces a build warning:
>
> WARNING: modpost: vmlinux: section mismatch in reference: 
> snp_probe_rmptable_info+0x95 (section: .text) -> x86_init (section: 
> .init.data)
> WARNING: modpost: vmlinux: section mismatch in reference: 
> snp_probe_rmptable_info+0x99 (section: .text) -> 
> snp_rmptable_e820_fixup (section: .init.text)
Oh, so this requires snp_probe_rmptable_info() to be fixed to use the 
__init macro.

I believe that snp_probe_rmptable_info() should be anyway using the 
__init macro and this fix for snp_probe_rmptable_info() needs to be sent 
as a separate patch and regardless of this patch getting merged or not.

Thanks, Ashish

> Thanks,
> Tom
>
> > +
> >       return true;
> >   }