linux-kernel - [RFC 12/16] x86/kvm: Share steal time page with host

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Date:   Fri, 22 May 2020 15:52:10 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     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>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
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>
Subject: [RFC 12/16] x86/kvm: Share steal time page with host

struct kvm_steal_time is shared between guest and host. Mark it as
shared.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/kernel/kvm.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index f50d65df4412..b0f445796ed1 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -286,11 +286,15 @@ static void kvm_register_steal_time(void)
 {
 	int cpu = smp_processor_id();
 	struct kvm_steal_time *st = &per_cpu(steal_time, cpu);
+	unsigned long phys;
 
 	if (!has_steal_clock)
 		return;
 
-	wrmsrl(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
+	phys = slow_virt_to_phys(st);
+	if (kvm_mem_protected())
+		kvm_hypercall2(KVM_HC_MEM_SHARE, phys >> PAGE_SHIFT, 1);
+	wrmsrl(MSR_KVM_STEAL_TIME, (phys | KVM_MSR_ENABLED));
 	pr_info("kvm-stealtime: cpu %d, msr %llx\n",
 		cpu, (unsigned long long) slow_virt_to_phys(st));
 }
-- 
2.26.2