From mboxrd@z Thu Jan 1 00:00:00 1970 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4D217C636D6 for ; Mon, 20 Feb 2023 20:54:11 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pUD5W-0000UK-Gj; Mon, 20 Feb 2023 15:48:42 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pUD51-0007a2-EO for qemu-devel@nongnu.org; Mon, 20 Feb 2023 15:48:24 -0500 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pUD4t-0003XK-QZ for qemu-devel@nongnu.org; Mon, 20 Feb 2023 15:48:07 -0500 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=R5rM5z7s7E4Lvv1hg+t9pUHA5+gYKakPc+YzUVV/gEg=; b=ecQjTs9ad1+kFos1gihkUy8pTW qGWE1qjHK+H9tYMgJL1arwFc4ZoJdvFuuOstyviQgbb4PQs2OAiUk/RR/MVP+SYV+PAJ/umQEEBik u+jOofUhCO0mNcULckhjuESNsMZU9v60jShr9lVmvZO1rI8i7C6ody1IK8i7A/Xq9VVGebxaXd8U5 5fv1coxy2uBa48YcqX3OPeDzXI1jvER94T5RdJ+mOamyKAXg4cET2XPf2n6fCkEK1omaCYWZeppc7 d+1KlPikcyQ1LvIFy8ulpBiL2tkOOnkE4J33yorUJvOmWuN86swaNLB+w7iut8V0UHRU5i0uVFvpN B0YOGGBg==; Received: from i7.infradead.org ([2001:8b0:10b:1:21e:67ff:fecb:7a92]) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1pUD4U-00BvKT-1l; Mon, 20 Feb 2023 20:47:47 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1pUD4U-00B4r8-1N; Mon, 20 Feb 2023 20:47:38 +0000 From: David Woodhouse To: Peter Maydell , qemu-devel@nongnu.org Cc: Paolo Bonzini , Paul Durrant , Joao Martins , Ankur Arora , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Thomas Huth , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Juan Quintela , "Dr . David Alan Gilbert" , Claudio Fontana , Julien Grall , "Michael S. Tsirkin" , Marcel Apfelbaum , armbru@redhat.com, Stefano Stabellini , vikram.garhwal@amd.com Subject: [PATCH v12 12/60] i386/xen: Implement SCHEDOP_poll and SCHEDOP_yield Date: Mon, 20 Feb 2023 20:46:48 +0000 Message-Id: <20230220204736.2639601-13-dwmw2@infradead.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230220204736.2639601-1-dwmw2@infradead.org> References: <20230220204736.2639601-1-dwmw2@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html Received-SPF: none client-ip=2001:8b0:10b:1:d65d:64ff:fe57:4e05; envelope-from=BATV+82aa7fb0aadd3de72584+7120+infradead.org+dwmw2@desiato.srs.infradead.org; helo=desiato.infradead.org X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: David Woodhouse They both do the same thing and just call sched_yield. This is enough to stop the Linux guest panicking when running on a host kernel which doesn't intercept SCHEDOP_poll and lets it reach userspace. Signed-off-by: David Woodhouse Reviewed-by: Paul Durrant --- target/i386/kvm/xen-emu.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c index 4ed833656f..ebea27caf6 100644 --- a/target/i386/kvm/xen-emu.c +++ b/target/i386/kvm/xen-emu.c @@ -234,6 +234,19 @@ static bool kvm_xen_hcall_sched_op(struct kvm_xen_exit *exit, X86CPU *cpu, err = schedop_shutdown(cs, arg); break; + case SCHEDOP_poll: + /* + * Linux will panic if this doesn't work. Just yield; it's not + * worth overthinking it because with event channel handling + * in KVM, the kernel will intercept this and it will never + * reach QEMU anyway. The semantics of the hypercall explicltly + * permit spurious wakeups. + */ + case SCHEDOP_yield: + sched_yield(); + err = 0; + break; + default: return false; } -- 2.39.0