From patchwork Sun Oct 6 10:46:36 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 11176289 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7674876 for ; Sun, 6 Oct 2019 10:47:40 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 490EF21479 for ; Sun, 6 Oct 2019 10:47:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="JR2ipiF/"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="mez2mYzE" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 490EF21479 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=1oqcG61ZlWzwbHlc72NnF/oBCvqth4JUgndFzst3NLg=; b=JR2ipiF/7GjDyE K8iMW/CX+YxQA7O0cb8O6JUQ88y9piMU/37FD85NKaZ9DaFID1x2KFgbPGik4/lxgatd3OIZaYR3J XAQ+idXaeKd4JlarDbjgdgnI9zJIwgA3s7Vi/c0nD0jP4+HvLJrlWsZh0tXed8iKNY7fh2XHRM8y0 PWieBBMR9WlgOGJf1fUgL8LQLNM8ShLFqTRe3qdBhVrTsjKTBQPku3UMZ0wy6RL1C3BSQS5VTwUEc DRwY56NhkO7UQ6wBkEp0nZK9eoryVH0wKdy24RKdjvzuA4zZV0byJFJQI3iAP7OhpXAici4TrtvuP RE6tpbSruTSpjZc1uoJg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1iH44e-00068J-8T; Sun, 06 Oct 2019 10:47:36 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.2 #3 (Red Hat Linux)) id 1iH44E-0005ga-8R for linux-arm-kernel@lists.infradead.org; Sun, 06 Oct 2019 10:47:11 +0000 Received: from localhost.localdomain (82-132-217-85.dab.02.net [82.132.217.85]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DE3C32084D; Sun, 6 Oct 2019 10:47:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570358829; bh=Kbjk8U9KY83YtrC+Vj1iMZXkRW6yshTSizjEOBVjj3c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mez2mYzED96KqrhBz67wivD2jw1wIwdikf3GrsDkzHasjg5QTgXSnijiFwjnfUbJy q13TxPAqD2mC4KN2lk89SDpLrAzbDj7P7FgMLg58iOXMyDyMTEIVHiS5U0hEnPsyow r6xpj6r4VNBE1Bvan82NC5l+sIsAwQ9Ok7USMXS0= From: maz@kernel.org To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org Subject: [PATCH 3/3] KVM: arm64: pmu: Reset sample period on overflow handling Date: Sun, 6 Oct 2019 11:46:36 +0100 Message-Id: <20191006104636.11194-4-maz@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191006104636.11194-1-maz@kernel.org> References: <20191006104636.11194-1-maz@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191006_034710_339785_6BCF400F X-CRM114-Status: GOOD ( 12.68 ) X-Spam-Score: -5.2 (-----) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (-5.2 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at https://www.dnswl.org/, high trust [198.145.29.99 listed in list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.0 DKIMWL_WL_HIGH DKIMwl.org - Whitelisted High sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Suzuki K Poulose , Marc Zyngier , James Morse , Andrew Murray , Julien Thierry Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: Marc Zyngier The PMU emulation code uses the perf event sample period to trigger the overflow detection. This works fine for the *first* overflow handling, but results in a huge number of interrupts on the host, unrelated to the number of interrupts handled in the guest (a x20 factor is pretty common for the cycle counter). On a slow system (such as a SW model), this can result in the guest only making forward progress at a glacial pace. It turns out that the clue is in the name. The sample period is exactly that: a period. And once the an overflow has occured, the following period should be the full width of the associated counter, instead of whatever the guest had initially programed. Reset the sample period to the architected value in the overflow handler, which now results in a number of host interrupts that is much closer to the number of interrupts in the guest. Fixes: b02386eb7dac ("arm64: KVM: Add PMU overflow interrupt routing") Signed-off-by: Marc Zyngier --- virt/kvm/arm/pmu.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/virt/kvm/arm/pmu.c b/virt/kvm/arm/pmu.c index c30c3a74fc7f..3ca4761fc0f5 100644 --- a/virt/kvm/arm/pmu.c +++ b/virt/kvm/arm/pmu.c @@ -444,6 +444,18 @@ static void kvm_pmu_perf_overflow(struct perf_event *perf_event, struct kvm_pmc *pmc = perf_event->overflow_handler_context; struct kvm_vcpu *vcpu = kvm_pmc_to_vcpu(pmc); int idx = pmc->idx; + u64 val, period; + + /* Start by resetting the sample period to the architectural limit */ + val = kvm_pmu_get_pair_counter_value(vcpu, pmc); + + if (kvm_pmu_idx_is_64bit(vcpu, pmc->idx)) + period = (-val) & GENMASK(63, 0); + else + period = (-val) & GENMASK(31, 0); + + pmc->perf_event->attr.sample_period = period; + pmc->perf_event->hw.sample_period = period; __vcpu_sys_reg(vcpu, PMOVSSET_EL0) |= BIT(idx);