Re: [RFC 0/3] Expose Confidential Computing capabilities on sysfs

[Dave Hansen]

On 3/9/22 14:06, Alejandro Jimenez wrote:>
> On EPYC Milan host:
> 
> $ grep -r . /sys/kernel/mm/mem_encrypt/*
> /sys/kernel/mm/mem_encrypt/c_bit_position:51

Why on earth would we want to expose this to userspace?

> /sys/kernel/mm/mem_encrypt/sev/nr_sev_asid:509
> /sys/kernel/mm/mem_encrypt/sev/status:enabled
> /sys/kernel/mm/mem_encrypt/sev/nr_asid_available:509
> /sys/kernel/mm/mem_encrypt/sev_es/nr_sev_es_asid:0
> /sys/kernel/mm/mem_encrypt/sev_es/status:enabled
> /sys/kernel/mm/mem_encrypt/sev_es/nr_asid_available:509
> /sys/kernel/mm/mem_encrypt/sme/status:active

For all of this...  What will userspace *do* with it?

For nr_asid_available, I get it.  It tells you how many guests you can
still run.  But, TDX will need the same logical thing.  Should TDX hosts
go looking for this in:

	/sys/kernel/mm/mem_encrypt/tdx/available_guest_key_ids

?

If it's something that's common, it needs to be somewhere common.