RE: [PATCH Part2 v6 05/49] x86/sev: Add RMP entry lookup helpers

Kalra, Ashish
2022-08-01T21:45:12Z

[AMD Official Use Only - General]

Hello Boris,

>> +static struct rmpentry *__snp_lookup_rmpentry(u64 pfn, int *level) {
>> + unsigned long vaddr, paddr = pfn << PAGE_SHIFT;
>> + struct rmpentry *entry, *large_entry;
>.> +
>> + if (!pfn_valid(pfn))
>> + return ERR_PTR(-EINVAL);
>> +
>> + if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
>> + return ERR_PTR(-ENXIO);

>That test should happen first.
Ok.

>> + vaddr = rmptable_start + rmptable_page_offset(paddr);

>Wait, what does that macro do?

>It takes the physical address and gives the offset from the beginning of the RMP table in VA space?

>So why don't you do

> entry = rmptable_entry(paddr)

>instead which simply gives you directly the entry in the RMP table with which you can work further?

>Instead of this macro doing half the work and then callers having to add the RMP start address and cast.

>And make it small function so that you can have typechecking too, while at it.

Ok, I will add a new corresponding rmptable_entry() function here, should be usable for getting the large
RMP entry below too.

>> + if (unlikely(vaddr > rmptable_end))
>> + return ERR_PTR(-ENXIO);
>> +
>> + entry = (struct rmpentry *)vaddr;
>> +
>> + /* Read a large RMP entry to get the correct page level used in RMP entry. */
>> + vaddr = rmptable_start + rmptable_page_offset(paddr & PMD_MASK);
>> + large_entry = (struct rmpentry *)vaddr;
>> + *level = RMP_TO_X86_PG_LEVEL(rmpentry_pagesize(large_entry));
>> +
>> + return entry;
>> +}
>> +
>> +/*
>> diff --git a/include/linux/sev.h b/include/linux/sev.h new file mode
>> 100644 index 000000000000..1a68842789e1
>> --- /dev/null
>> +++ b/include/linux/sev.h

>Why is this header in the linux/ namespace and not in arch/x86/ ?

>All that stuff in here doesn't have any meaning outside of x86...

Yes, makes sense to move it to arch/x86.

Thanks,
Ashish