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Tue, 12 May 2026 13:12:21 -0700 (PDT) Received: from [192.168.10.48] ([176.206.106.181]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4548e4bbebdsm38633856f8f.5.2026.05.12.13.12.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2026 13:12:20 -0700 (PDT) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Sean Christopherson Cc: yosry@kernel.org, Maxim Levitsky , David Kaplan Subject: [PATCH v2] KVM: nSVM: Never use L0's PAUSE loop exiting while L2 is running Date: Tue, 12 May 2026 22:12:19 +0200 Message-ID: <20260512201219.3021354-1-pbonzini@redhat.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260508213321.373309-1-seanjc@google.com> References: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On 5/8/26 23:33, Sean Christopherson wrote:=0D > Never use L0's (KVM's) PAUSE loop exiting controls while L2 is running,=0D > and instead always configure vmcb02 according to L1's exact capabilities= =0D > and desires.=0D =0D Queued, thanks. While I didn't go as far as splitting in two commits,=0D I did apply a more or less cosmetic tweak to the WARNs. Calling=0D grow_ple_window/shrink_ple_window with PLE disabled is harmless but=0D also makes little sense. This can be represented by a WARN that=0D does not have an early return.=0D =0D The WARN condition is obviously false for shrink_ple_window and=0D a little less obviously so for grow_ple_window, but in case any=0D other callers are added it can be useful to have it as a heads up.=0D =0D Paolo=0D =0D diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c=0D index ac21f402c1ca..e02a38da5296 100644=0D --- a/arch/x86/kvm/svm/svm.c=0D +++ b/arch/x86/kvm/svm/svm.c=0D @@ -913,12 +913,15 @@ static void grow_ple_window(struct kvm_vcpu *vcpu)=0D struct vmcb_control_area *control =3D &svm->vmcb->control;=0D int old =3D control->pause_filter_count;=0D =0D + /* Adjusting pause_filter_count makes no sense if PLE is disabled. */=0D + WARN_ON_ONCE(kvm_pause_in_guest(vcpu->kvm));=0D +=0D /*=0D * While running L2, KVM should intercept PAUSE if and only if L1 wants=0D * to intercept PAUSE, and L1's intercept should take priority, i.e.=0D * KVM should never handle a PAUSE intercept from L2.=0D */=0D - if (WARN_ON_ONCE(is_guest_mode(vcpu) || kvm_pause_in_guest(vcpu->kvm)))=0D + if (WARN_ON_ONCE(is_guest_mode(vcpu)))=0D return;=0D =0D control->pause_filter_count =3D __grow_ple_window(old,=0D (1/2) Stage this hunk [y,n,q,a,d,k,K,j,J,g,/,s,e,p,P,?]? y=0D @@ -939,6 +942,9 @@ static void shrink_ple_window(struct kvm_vcpu *vcpu)=0D struct vmcb_control_area *control =3D &svm->vmcb->control;=0D int old =3D control->pause_filter_count;=0D =0D + /* Adjusting pause_filter_count makes no sense if PLE is disabled. */=0D + WARN_ON_ONCE(kvm_pause_in_guest(vcpu->kvm));=0D +=0D if (is_guest_mode(vcpu))=0D return;=0D =0D =0D =0D