From patchwork Mon Oct 16 15:18:59 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 13423559 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85EA6CDB474 for ; Mon, 16 Oct 2023 15:19:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233821AbjJPPTo (ORCPT ); Mon, 16 Oct 2023 11:19:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50116 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231569AbjJPPTl (ORCPT ); Mon, 16 Oct 2023 11:19:41 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED4D2AB for ; Mon, 16 Oct 2023 08:19:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=sLSQjDyHM6H6vyCwrNd1oC0DrClv2UPw9aKIA6AhbP0=; b=FqeMYA/JfTC8p0DG5XK/5ZIu7B EUetaVF1ix6DTUyqYJPmR6BEKr8LA+088i3w5FooNB+tJ2CGq5fIwEk6CHqTMqRWi4A4JkeZDj4PO FFVaxZlOnTksjcWikg7PxddJcMky3TKcRovSYEeLHXsu9U/2HJZfBr2d77FPfZMF9Lw1bhqNl7arM I7LF7ZN8+aIXN0kV7FUmX70qmrghYiYcTbPPqJb6BE4mD4zOv1LHUL/J+w/UCAeu+v78F92hv3ea5 KYP7zA2OShwtZ30hVrz5y3VZ46/VNhecSXsjdugWtI+wFOhgX2X++SXZeSAtEBesjmULCUOv8BaMW +MTswpPQ==; Received: from [2001:8b0:10b:1::ebe] (helo=i7.infradead.org) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1qsPNB-0067AG-2H; Mon, 16 Oct 2023 15:19:15 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qsPNB-0005nB-2D; Mon, 16 Oct 2023 16:19:13 +0100 From: David Woodhouse To: qemu-devel@nongnu.org Cc: Kevin Wolf , Hanna Reitz , Stefano Stabellini , Anthony Perard , Paul Durrant , =?utf-8?q?Marc-Andr=C3=A9_Lureau?= , Paolo Bonzini , "Michael S. Tsirkin" , Marcel Apfelbaum , Richard Henderson , Eduardo Habkost , David Woodhouse , Marcelo Tosatti , qemu-block@nongnu.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org Subject: [PATCH 02/12] hw/xen: select kernel mode for per-vCPU event channel upcall vector Date: Mon, 16 Oct 2023 16:18:59 +0100 Message-Id: <20231016151909.22133-3-dwmw2@infradead.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231016151909.22133-1-dwmw2@infradead.org> References: <20231016151909.22133-1-dwmw2@infradead.org> MIME-Version: 1.0 Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: David Woodhouse A guest which has configured the per-vCPU upcall vector may set the HVM_PARAM_CALLBACK_IRQ param to fairly much anything other than zero. For example, Linux v6.0+ after commit b1c3497e604 ("x86/xen: Add support for HVMOP_set_evtchn_upcall_vector") will just do this after setting the vector: /* Trick toolstack to think we are enlightened. */ if (!cpu) rc = xen_set_callback_via(1); That's explicitly setting the delivery to GSI#, but it's supposed to be overridden by the per-vCPU vector setting. This mostly works in QEMU *except* for the logic to enable the in-kernel handling of event channels, which falsely determines that the kernel cannot accelerate GSI delivery in this case. Add a kvm_xen_has_vcpu_callback_vector() to report whether vCPU#0 has the vector set, and use that in xen_evtchn_set_callback_param() to enable the kernel acceleration features even when the param *appears* to be set to target a GSI. Preserve the Xen behaviour that when HVM_PARAM_CALLBACK_IRQ is set to *zero* the event channel delivery is disabled completely. (Which is what that bizarre guest behaviour is working round in the first place.) Fixes: 91cce756179 ("hw/xen: Add xen_evtchn device for event channel emulation") Signed-off-by: David Woodhouse --- hw/i386/kvm/xen_evtchn.c | 6 ++++++ include/sysemu/kvm_xen.h | 1 + target/i386/kvm/xen-emu.c | 7 +++++++ 3 files changed, 14 insertions(+) diff --git a/hw/i386/kvm/xen_evtchn.c b/hw/i386/kvm/xen_evtchn.c index 4df973022c..d72dca6591 100644 --- a/hw/i386/kvm/xen_evtchn.c +++ b/hw/i386/kvm/xen_evtchn.c @@ -490,6 +490,12 @@ int xen_evtchn_set_callback_param(uint64_t param) break; } + /* If the guest has set a per-vCPU callback vector, prefer that. */ + if (gsi && kvm_xen_has_vcpu_callback_vector()) { + in_kernel = kvm_xen_has_cap(EVTCHN_SEND); + gsi = 0; + } + if (!ret) { /* If vector delivery was turned *off* then tell the kernel */ if ((s->callback_param >> CALLBACK_VIA_TYPE_SHIFT) == diff --git a/include/sysemu/kvm_xen.h b/include/sysemu/kvm_xen.h index 595abfbe40..961c702c4e 100644 --- a/include/sysemu/kvm_xen.h +++ b/include/sysemu/kvm_xen.h @@ -22,6 +22,7 @@ int kvm_xen_soft_reset(void); uint32_t kvm_xen_get_caps(void); void *kvm_xen_get_vcpu_info_hva(uint32_t vcpu_id); +bool kvm_xen_has_vcpu_callback_vector(void); void kvm_xen_inject_vcpu_callback_vector(uint32_t vcpu_id, int type); void kvm_xen_set_callback_asserted(void); int kvm_xen_set_vcpu_virq(uint32_t vcpu_id, uint16_t virq, uint16_t port); diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c index b49a840438..477e93cd92 100644 --- a/target/i386/kvm/xen-emu.c +++ b/target/i386/kvm/xen-emu.c @@ -424,6 +424,13 @@ void kvm_xen_set_callback_asserted(void) } } +bool kvm_xen_has_vcpu_callback_vector(void) +{ + CPUState *cs = qemu_get_cpu(0); + + return cs && !!X86_CPU(cs)->env.xen_vcpu_callback_vector; +} + void kvm_xen_inject_vcpu_callback_vector(uint32_t vcpu_id, int type) { CPUState *cs = qemu_get_cpu(vcpu_id);