Re: [PATCH v5 18/26] powerpc/book3s64/keys/kuap: Reset AMR/IAMR values on kexec

On 7/6/20 5:59 PM, Michael Ellerman wrote:

"Aneesh Kumar K.V" [off-list ref] writes:

quoted

As we kexec across kernels that use AMR/IAMR for different purposes
we need to ensure that new kernels get kexec'd with a reset value
of AMR/IAMR. For ex: the new kernel can use key 0 for kernel mapping and the old
AMR value prevents access to key 0.

This patch also removes reset if IAMR and AMOR in kexec_sequence. Reset of AMOR
is not needed and the IAMR reset is partial (it doesn't do the reset
on secondary cpus) and is redundant with this patch.

I like the idea of cleaning this stuff up.

But I think tying it into kup/kuep/kuap and the MMU features and ifdefs
and so on is overly complicated.

We should just have eg:

void reset_sprs(void)
{
	if (early_cpu_has_feature(CPU_FTR_ARCH_206)) {
         	mtspr(SPRN_AMR, 0);
         	mtspr(SPRN_UAMOR, 0);
         }

	if (early_cpu_has_feature(CPU_FTR_ARCH_207S)) {
         	mtspr(SPRN_IAMR, 0);
         }
}

And call that from the kexec paths.

Will fix. Should that be early_cpu_has_feature()? cpu_has_feature() 
should work there right?

-aneesh