Re: [RFCv2 00/16] KVM protected memory extension

[Vitaly Kuznetsov]

"Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> writes:

> On Wed, Oct 21, 2020 at 04:46:48PM +0200, Vitaly Kuznetsov wrote:
>> "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> writes:
>> 
>> > Maybe it would be cleaner to handle reboot in userspace? If we got the VM
>> > rebooted, just reconstruct it from scratch as if it would be new boot.
>> 
>> We are definitely not trying to protect against malicious KVM so maybe
>> we can do the cleanup there (when protection was enabled) so we can
>> unprotect everything without risk of a leak?
>
> Do you have any particular codepath in mind? I didn't find anything
> suitable so far.

I didn't put much thought in it but e.g. on x86, what if we put this to
kvm_vcpu_reset() under 'if (kvm_vcpu_is_bsp())' condition? 

The main problem I see is that we can't clean up *all* memory,
e.g. firmware related stuff should stay intact and this contraducts your
KVM_HC_ENABLE_MEM_PROTECTED which protects everything. We can, probably,
get rid of it leaving KVM_HC_MEM_SHARE/KVM_HC_MEM_UNSHARE only shifting
responsibility to define what can be cleaned up on the guest kernel
(stating in the doc that all protected memory will get whiped out on
reboot).

-- 
Vitaly