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

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Message-ID: <875zck82fx.fsf@vitty.brq.redhat.com>
Date:   Mon, 25 May 2020 17:22:10 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     David Rientjes <rientjes@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Will Drewry <wad@...omium.org>,
        "Edgecombe\, Rick P" <rick.p.edgecombe@...el.com>,
        "Kleen\, Andi" <andi.kleen@...el.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [RFC 13/16] x86/kvmclock: Share hvclock memory with the host

"Kirill A. Shutemov" <kirill@...temov.name> 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@...ux.intel.com>
> ---
>  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)

-- 
Vitaly