Re: [RFC 13/16] x86/kvmclock: Share hvclock memory with the host

[Kirill A. Shutemov]

On Mon, May 25, 2020 at 05:22:10PM +0200, Vitaly Kuznetsov wrote:
> "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> writes:
> 
> > hvclock is shared between the guest and the hypervisor. It has to be
> > accessible by host.
> >
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> > ---
> >  arch/x86/kernel/kvmclock.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> > index 34b18f6eeb2c..ac6c2abe0d0f 100644
> > --- a/arch/x86/kernel/kvmclock.c
> > +++ b/arch/x86/kernel/kvmclock.c
> > @@ -253,7 +253,7 @@ static void __init kvmclock_init_mem(void)
> >  	 * hvclock is shared between the guest and the hypervisor, must
> >  	 * be mapped decrypted.
> >  	 */
> > -	if (sev_active()) {
> > +	if (sev_active() || kvm_mem_protected()) {
> >  		r = set_memory_decrypted((unsigned long) hvclock_mem,
> >  					 1UL << order);
> >  		if (r) {
> 
> Sorry if I missed something but we have other structures which KVM guest
> share with the host,
> 
> sev_map_percpu_data():
> ...
> 	for_each_possible_cpu(cpu) {
> 		__set_percpu_decrypted(&per_cpu(apf_reason, cpu), sizeof(apf_reason));
> 		__set_percpu_decrypted(&per_cpu(steal_time, cpu), sizeof(steal_time));
> 		__set_percpu_decrypted(&per_cpu(kvm_apic_eoi, cpu), sizeof(kvm_apic_eoi));
> 	}
> ...
> 
> Do you handle them somehow in the patchset? (I'm probably just blind
> failing to see how 'early_set_memory_decrypted()' is wired up)

I don't handle them yet: I've seen the function, but have not modified it.
I want to understand first why it doesn't blow up for me without the
change. Any clues?

-- 
 Kirill A. Shutemov