From patchwork Thu Oct 19 15:39:59 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Woodhouse X-Patchwork-Id: 13429415 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 82149CDB483 for ; Thu, 19 Oct 2023 15:41:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345596AbjJSPlA (ORCPT ); Thu, 19 Oct 2023 11:41:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51486 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345727AbjJSPk6 (ORCPT ); Thu, 19 Oct 2023 11:40:58 -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 6C81B126 for ; Thu, 19 Oct 2023 08:40:53 -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=yj3bQOsvlVS+cuxN5wPLkNEIrT6cixfjryf2/rFkYPo=; b=apmrUQjys+v5rup9nz+m2AM5cJ 2Y2A05kFFcMK4lO0kAHJWQYvJuY7yW0Mbcd6xBkSdi7dZE8UYfHwT+MsBjpnPbxyw76XY0z6pWZIQ /Xbt2G1fOgOADjjv0bJg895NrBPYCnkgVjKTWWOXLkLH7it8HqWs9l/FFJgQ/mUgEiAcalOp8D8Wy qH7vnVOom93dI6oaB21y/lpt2E7eoveScrTU88jzuNmmhGwUA3Tinnyl0/mIZt9MdWKMLq3ME3d3a hd4UWY3+BnlXQGAEpOmqrAsqGKgxLgM6NjTY7kgwl4SAKcduwn8Pjydd4w/+pVV6+TRVb9aodRCJm 9DCTuMag==; 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 1qtV8M-009yCk-2Y; Thu, 19 Oct 2023 15:40:27 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qtV8L-000Pto-2c; Thu, 19 Oct 2023 16:40:25 +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 , Richard Henderson , Eduardo Habkost , "Michael S. Tsirkin" , Marcel Apfelbaum , Jason Wang , Marcelo Tosatti , Cleber Rosa , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , Wainer dos Santos Moschetta , Beraldo Leal , qemu-block@nongnu.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, Bernhard Beschow , Joel Upham Subject: [PATCH v2 03/24] hw/xen: select kernel mode for per-vCPU event channel upcall vector Date: Thu, 19 Oct 2023 16:39:59 +0100 Message-Id: <20231019154020.99080-4-dwmw2@infradead.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20231019154020.99080-1-dwmw2@infradead.org> References: <20231019154020.99080-1-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#1, 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 Reviewed-by: Paul Durrant --- 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 a731738411..3d6f4b4a0a 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 619240398a..3ba636b09a 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);