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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 142D7C25B0C for ; Tue, 9 Aug 2022 18:18:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345882AbiHISPs (ORCPT ); Tue, 9 Aug 2022 14:15:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57454 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345319AbiHISMe (ORCPT ); Tue, 9 Aug 2022 14:12:34 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 01AA12C10F; Tue, 9 Aug 2022 11:05:32 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 6D1F7B816EC; Tue, 9 Aug 2022 18:05:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 85FB8C43141; Tue, 9 Aug 2022 18:05:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660068330; bh=7JuMXb46I3k4p+22YYaGhNRUrgtDA9PM5o70vGc8J40=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SiatDWAnaYg3/JetnmGg6trzRZyM6UHpODZEh+iq4G/9o59M1Cjt8n8xHJslRIcjJ +WJnhmip8j0MQRc+gLuHopAgXptkFUtVTHPhoa+0s+pLhhInR2lqYijze3CJpBqZFX DGIgqcryPkRpI8stum46NRqTXv3pHD5aaaaoJ+dU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sean Christopherson , Paolo Bonzini , Sasha Levin Subject: [PATCH 5.15 11/30] KVM: x86: do not set st->preempted when going back to user space Date: Tue, 9 Aug 2022 20:00:36 +0200 Message-Id: <20220809175514.713107597@linuxfoundation.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220809175514.276643253@linuxfoundation.org> References: <20220809175514.276643253@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Paolo Bonzini [ Upstream commit 54aa83c90198e68eee8b0850c749bc70efb548da ] Similar to the Xen path, only change the vCPU's reported state if the vCPU was actually preempted. The reason for KVM's behavior is that for example optimistic spinning might not be a good idea if the guest is doing repeated exits to userspace; however, it is confusing and unlikely to make a difference, because well-tuned guests will hardly ever exit KVM_RUN in the first place. Suggested-by: Sean Christopherson Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- arch/x86/kvm/x86.c | 26 ++++++++++++++------------ arch/x86/kvm/xen.h | 6 ++++-- 2 files changed, 18 insertions(+), 14 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b2436796e03c..8a6ee5d8adc7 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4415,19 +4415,21 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) { int idx; - if (vcpu->preempted && !vcpu->arch.guest_state_protected) - vcpu->arch.preempted_in_kernel = !static_call(kvm_x86_get_cpl)(vcpu); + if (vcpu->preempted) { + if (!vcpu->arch.guest_state_protected) + vcpu->arch.preempted_in_kernel = !static_call(kvm_x86_get_cpl)(vcpu); - /* - * Take the srcu lock as memslots will be accessed to check the gfn - * cache generation against the memslots generation. - */ - idx = srcu_read_lock(&vcpu->kvm->srcu); - if (kvm_xen_msr_enabled(vcpu->kvm)) - kvm_xen_runstate_set_preempted(vcpu); - else - kvm_steal_time_set_preempted(vcpu); - srcu_read_unlock(&vcpu->kvm->srcu, idx); + /* + * Take the srcu lock as memslots will be accessed to check the gfn + * cache generation against the memslots generation. + */ + idx = srcu_read_lock(&vcpu->kvm->srcu); + if (kvm_xen_msr_enabled(vcpu->kvm)) + kvm_xen_runstate_set_preempted(vcpu); + else + kvm_steal_time_set_preempted(vcpu); + srcu_read_unlock(&vcpu->kvm->srcu, idx); + } static_call(kvm_x86_vcpu_put)(vcpu); vcpu->arch.last_host_tsc = rdtsc(); diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h index cc0cf5f37450..a7693a286e40 100644 --- a/arch/x86/kvm/xen.h +++ b/arch/x86/kvm/xen.h @@ -97,8 +97,10 @@ static inline void kvm_xen_runstate_set_preempted(struct kvm_vcpu *vcpu) * behalf of the vCPU. Only if the VMM does actually block * does it need to enter RUNSTATE_blocked. */ - if (vcpu->preempted) - kvm_xen_update_runstate_guest(vcpu, RUNSTATE_runnable); + if (WARN_ON_ONCE(!vcpu->preempted)) + return; + + kvm_xen_update_runstate_guest(vcpu, RUNSTATE_runnable); } /* 32-bit compatibility definitions, also used natively in 32-bit build */ -- 2.35.1