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 X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 944EEC4360C for ; Sun, 6 Oct 2019 10:47:14 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 4BC302084D for ; Sun, 6 Oct 2019 10:47:14 +0000 (UTC) Authentication-Results: mail.kernel.org; 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 4BC302084D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 03C624A529; Sun, 6 Oct 2019 06:47:14 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@kernel.org Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id e-7OzupM6M0B; Sun, 6 Oct 2019 06:47:12 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 55C984A7F3; Sun, 6 Oct 2019 06:47:12 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8D9184A54B for ; Sun, 6 Oct 2019 06:47:11 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id vYT4Rq5AYpk6 for ; Sun, 6 Oct 2019 06:47:10 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 8238F4A535 for ; Sun, 6 Oct 2019 06:47:10 -0400 (EDT) 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 Cc: Marc Zyngier X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu 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); -- 2.20.1 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm