RE: [PATCH Part2 v6 03/49] x86/sev: Add the host SEV-SNP initialization support

Kalra, Ashish
2022-07-19T11:35:05Z

[AMD Official Use Only - General]

Hello Boris,

>> > That section number will change over time - if you want to refer to
>> > some section just use its title so that people can at least grep for
>> > the relevant text.
>>
>> This will all go into sev.c, instead of the header file, as this is
>> non-architectural and per-processor and the structure won't be exposed
>> to the rest of the kernel. The above PPR reference and potentially in
>> future an architectural method of reading the RMP table entries will
>> be moved into it.

>I fail to see how this addresses my comment... All I'm saying is, the "section 2.1.4.2" number will change so don't quote it in the text but quote the section *name* instead.

Yes I agree with your comments, all I am saying is that these comments will move into sev.c instead of the header file.

>> I believe that with kexec and after issuing the shutdown command, the
>> RMP table needs to be fully initialized, so we should be
>> re-initializing the RMP table to zero here.

>And yet you're doing:

> /*
> * Check if SEV-SNP is already enabled, this can happen if we are coming from
> * kexec boot.
> */
> rdmsrl(MSR_AMD64_SYSCFG, val);
> if (val & MSR_AMD64_SYSCFG_SNP_EN)
> goto skip_enable; <-------- skip zeroing

>So which is it?

Again what I meant is that this will be fixed to reset the RMP table for kexec boot too.

>> Yes, IOMMU is enforced for SNP to ensure that HV cannot program DMA
>> directly into guest private memory. In case of SNP, the IOMMU makes
>> sure that the page(s) used for DMA are HV owned.

>>Yes, now put that in the comment above the

> fs_initcall(snp_rmptable_init);

>line.

Yes.

Thanks,
Ashish