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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81465C433EF for ; Fri, 8 Oct 2021 11:32:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 69B2961374 for ; Fri, 8 Oct 2021 11:32:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241169AbhJHLeM (ORCPT ); Fri, 8 Oct 2021 07:34:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:58556 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240877AbhJHLcS (ORCPT ); Fri, 8 Oct 2021 07:32:18 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8BE94610E7; Fri, 8 Oct 2021 11:30:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1633692613; bh=0C6W9SS6dd73z7EPUbhKn1NEfkcIH093yC9t/+PUAUg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=umG0zKTx5e4i+OFEcI8rmJ6FXBu5WOZ5dRSXGBwqdONT6iZwQg3Qqp0pYfE9teIs6 SNGUf3lSfc5u9VI1wz1smYUVlObRlCO/IbGTjSv4bfBj3MQfEVMK5XjNIxDYpcsJlF Xohe3wLWX42dLqfiSH1J0hADeejM/XDp3xew6mUw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sergey Senozhatsky , Paolo Bonzini , Sasha Levin Subject: [PATCH 5.4 12/16] KVM: do not shrink halt_poll_ns below grow_start Date: Fri, 8 Oct 2021 13:28:02 +0200 Message-Id: <20211008112715.875188234@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20211008112715.444305067@linuxfoundation.org> References: <20211008112715.444305067@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: Sergey Senozhatsky [ Upstream commit ae232ea460888dc5a8b37e840c553b02521fbf18 ] grow_halt_poll_ns() ignores values between 0 and halt_poll_ns_grow_start (10000 by default). However, when we shrink halt_poll_ns we may fall way below halt_poll_ns_grow_start and endup with halt_poll_ns values that don't make a lot of sense: like 1 or 9, or 19. VCPU1 trace (halt_poll_ns_shrink equals 2): VCPU1 grow 10000 VCPU1 shrink 5000 VCPU1 shrink 2500 VCPU1 shrink 1250 VCPU1 shrink 625 VCPU1 shrink 312 VCPU1 shrink 156 VCPU1 shrink 78 VCPU1 shrink 39 VCPU1 shrink 19 VCPU1 shrink 9 VCPU1 shrink 4 Mirror what grow_halt_poll_ns() does and set halt_poll_ns to 0 as soon as new shrink-ed halt_poll_ns value falls below halt_poll_ns_grow_start. Signed-off-by: Sergey Senozhatsky Signed-off-by: Paolo Bonzini Message-Id: <20210902031100.252080-1-senozhatsky@chromium.org> Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- virt/kvm/kvm_main.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 77f84cbca740..f31976010622 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2470,15 +2470,19 @@ out: static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu) { - unsigned int old, val, shrink; + unsigned int old, val, shrink, grow_start; old = val = vcpu->halt_poll_ns; shrink = READ_ONCE(halt_poll_ns_shrink); + grow_start = READ_ONCE(halt_poll_ns_grow_start); if (shrink == 0) val = 0; else val /= shrink; + if (val < grow_start) + val = 0; + vcpu->halt_poll_ns = val; trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, val, old); } -- 2.33.0