linux-kernel - [PATCH 08/10] KVM: x86: APICv: drop immediate APICv disablement on current vCPU

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: <20210623113002.111448-9-mlevitsk@redhat.com>
Date:   Wed, 23 Jun 2021 14:30:00 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Joerg Roedel <joro@...tes.org>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel@...r.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND
        64-BIT)),
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 08/10] KVM: x86: APICv: drop immediate APICv disablement on current vCPU

Special case of disabling the APICv on the current vCPU right away in
kvm_request_apicv_update doesn't bring much benefit vs raising
KVM_REQ_APICV_UPDATE on it instead, since this request will be processed
on the next entry to the guest.
(the comment about having another #VMEXIT is wrong).

It also hides various assumptions, that APICv enable state matches
the APICv inhibit state, as this special case only makes those states
match on the current vCPU.

Previous patches fixed few such assumptions so now it should be safe
to drop this special case.

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/x86.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6f0d9c231249..dcf06acdbf52 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9209,7 +9209,6 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_update_apicv);
  */
 void kvm_request_apicv_update(struct kvm *kvm, bool activate, ulong bit)
 {
-	struct kvm_vcpu *except;
 	unsigned long old, new, expected;
 
 	if (!kvm_x86_ops.check_apicv_inhibit_reasons ||
@@ -9237,18 +9236,9 @@ void kvm_request_apicv_update(struct kvm *kvm, bool activate, ulong bit)
 	if (kvm_x86_ops.pre_update_apicv_exec_ctrl)
 		static_call(kvm_x86_pre_update_apicv_exec_ctrl)(kvm, activate);
 
-	/*
-	 * Sending request to update APICV for all other vcpus,
-	 * while update the calling vcpu immediately instead of
-	 * waiting for another #VMEXIT to handle the request.
-	 */
-	except = kvm_get_running_vcpu();
-	kvm_make_all_cpus_request_except(kvm, KVM_REQ_APICV_UPDATE,
-					 except);
+	kvm_make_all_cpus_request(kvm, KVM_REQ_APICV_UPDATE);
 
 	kvm_allow_guest_entries(kvm);
-	if (except)
-		kvm_vcpu_update_apicv(except);
 }
 EXPORT_SYMBOL_GPL(kvm_request_apicv_update);
 
-- 
2.26.3