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 05BE6C433F5 for ; Wed, 6 Oct 2021 13:30:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E2F6E611C6 for ; Wed, 6 Oct 2021 13:30:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238904AbhJFNcY (ORCPT ); Wed, 6 Oct 2021 09:32:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:48804 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238668AbhJFNcS (ORCPT ); Wed, 6 Oct 2021 09:32:18 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id EE5C66115A; Wed, 6 Oct 2021 13:30:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1633527026; bh=WrArq5TDbHCcIBLOTgr1Em1sBBFfw26b3uB3ADisu30=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Z279v6kGkQU8MSHS2EUfhAOr78s9rZodOH/lQet7DLODpTiY0SdNjytOIt+AopO0R eCSHeA8sGwNR7uW+2OSThAeQ2Tr0YP3ZdSypiYz+AROc8H+vlpafphzKZy5S+fdtkk nVjyQHFXmXNOIcklnMGTwOdJsQ7OthHErji0RhMMDwCfS3Z+IBhvGiMb3uaijZ9KRF 5vzj6mn8ONabGH1SRaPnnpWvg6trNJE6rRgabfR6GaxBP2Kg0KXRwSHWPHRmY9Bkd8 SMnevOiifP8YWdM2tcnZWqG8/irO2lqe9tTruZ6sToQ4n8/Nhp7LuFgDocr/zCy4wG CSJbXH6se29Hw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sergey Senozhatsky , Paolo Bonzini , Sasha Levin , kvm@vger.kernel.org Subject: [PATCH MANUALSEL 5.14 3/9] KVM: do not shrink halt_poll_ns below grow_start Date: Wed, 6 Oct 2021 09:30:15 -0400 Message-Id: <20211006133021.271905-3-sashal@kernel.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20211006133021.271905-1-sashal@kernel.org> References: <20211006133021.271905-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@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 b50dbe269f4b..1a11dcb670a3 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3053,15 +3053,19 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu) 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