linux-kernel - [PATCH v3 29/37] KVM: VMX: Don't reload APIC access page if its control is disabled

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200320212833.3507-30-sean.j.christopherson@intel.com>
Date:   Fri, 20 Mar 2020 14:28:25 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     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>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ben Gardon <bgardon@...gle.com>,
        Junaid Shahid <junaids@...gle.com>,
        Liran Alon <liran.alon@...cle.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        John Haxby <john.haxby@...cle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: [PATCH v3 29/37] KVM: VMX: Don't reload APIC access page if its control is disabled

Don't reload the APIC access page if its control is disabled, e.g. if
the guest is running with x2APIC (likely) or with the local APIC
disabled (unlikely), to avoid unnecessary TLB flushes and VMWRITEs.
Unconditionally reload the APIC access page and flush the TLB when
the guest's virtual APIC transitions to "xAPIC enabled", as any
changes to the APIC access page's mapping will not be recorded while
the guest's virtual APIC is disabled.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e8d409b50afd..d49d2a1ddf03 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6122,7 +6122,15 @@ void vmx_set_virtual_apic_mode(struct kvm_vcpu *vcpu)
 		if (flexpriority_enabled) {
 			sec_exec_control |=
 				SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
-			vmx_flush_tlb_current(vcpu);
+			kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);
+
+			/*
+			 * Flush the TLB, reloading the APIC access page will
+			 * only do so if its physical address has changed, but
+			 * the guest may have inserted a non-APIC mapping into
+			 * the TLB while the APIC access page was disabled.
+			 */
+			kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu);
 		}
 		break;
 	case LAPIC_MODE_X2APIC:
@@ -6146,6 +6154,10 @@ static void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu)
 		return;
 	}
 
+	if (!(secondary_exec_controls_get(to_vmx(vcpu)) &
+	    SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES))
+		return;
+
 	page = gfn_to_page(vcpu->kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
 	if (is_error_page(page))
 		return;
-- 
2.24.1