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 CAEE9C7EE29 for ; Thu, 8 Jun 2023 22:06:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229644AbjFHWG0 (ORCPT ); Thu, 8 Jun 2023 18:06:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46908 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231445AbjFHWGY (ORCPT ); Thu, 8 Jun 2023 18:06:24 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CCB1A30D4 for ; Thu, 8 Jun 2023 15:06:23 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-babb79a17b8so1596280276.0 for ; Thu, 08 Jun 2023 15:06:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1686261982; x=1688853982; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=tdKizssFsMQJzj8/wSt0vRuPFuTT8IrX+6c5/ZqQtUU=; b=pYi5twzK16pe/u6UpDUsq5/gZ7VstFYaQpSoVInd6hIj+oSGhYPXPylVFxcNSuyTfw wCt/PuskPgVKlLP4RTlX1/zs0+7HkXHCX4XS7if1kU6ECFkPaPA6XhFNVqu9JjsX2WO/ 6WqFpH3dBOcrzKhywdtBIapeXoWXFx6aay6wJ/Qn7Ov7MwhcjCvIcth7YseBLy8rA6Ov 3DWI59xmNFppvf7woPF6SLT4FB7lfdwPzuUsRo9pwvg0hPnS8pOlnHx7+zVUdbb0FVld p5m22USbLg8gn8rqzTBnF1FE/reHbyRKFfM6g+eovhC7zK7inCcLfL8yF7dcAeB22C5F IZfg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1686261982; x=1688853982; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=tdKizssFsMQJzj8/wSt0vRuPFuTT8IrX+6c5/ZqQtUU=; b=WJK81RO4QJxEcIZ+MCCiWKHOKfvFq8WC2NY29gbb9w126XhNE6Q62TC+eVyQBRc6zD WL1EJJ7MrZSGQ4rKde3IDYbCrOyMXgPZ7N9b8RPh8uOVTTVi2KIpsBZjjHNqgtc+isjs HhCAJGqAwULgD6rwVAVBmxWDZEQO9yZ/3W3j+sXoDxp2aPGFE8HoxS63z1nOIVdIXJ66 uIaTLA9rF8nRLcfW1BKF/Eudcha05ncl1zkMpxShfOFAiiP2NxmQ7y+L8QmiI2B82dJx Dyq9wSRn+RRfLPqCDTmyrA7M4xGvdPT4cPZhwxgoA+F6vwpkr8y4ZCCqT/G2P/MjPeP3 EdHw== X-Gm-Message-State: AC+VfDzfrAl3mI8oh0ilHccyRX2NXoNkUwKIq8S3aKDKYd08Fv7O58VK 5ZtG142shCe63LjdeyqJxh5u9FBytlSsOO/4o8x4Sfv1b9UWi/LMxqcNoGg+737solIfSaDBqUX MpOmgdtJcHh9x5XzN7ZiwStYeqkMn3mubHi0WEvCb4pBebtCTjkEQUYsiyIll7+4LIE+Njw== X-Google-Smtp-Source: ACHHUZ4KfiB8l1+dUoVGrkHr93Y38MLg1AxejqBfztTpsuysMtbSy6a+JxAixUHY2sVHAQ46IvK3wvSRaY8= X-Received: from colette.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:5cff]) (user=ctshao job=sendgmr) by 2002:a05:6902:691:b0:ba8:1f20:ff4f with SMTP id i17-20020a056902069100b00ba81f20ff4fmr517992ybt.12.1686261982675; Thu, 08 Jun 2023 15:06:22 -0700 (PDT) Date: Thu, 8 Jun 2023 15:05:39 -0700 In-Reply-To: <20230608220558.39094-1-ctshao@google.com> Mime-Version: 1.0 References: <20230608220558.39094-1-ctshao@google.com> X-Mailer: git-send-email 2.41.0.162.gfafddb0af9-goog Message-ID: <20230608220558.39094-2-ctshao@google.com> Subject: [PATCH v1 2/3] KVM: arm64: Only initiate walk if page_count() > 1 in free_removed_table() From: Chun-Tse Shao To: linux-kernel@vger.kernel.org, yuzhao@google.com, oliver.upton@linux.dev Cc: Chun-Tse Shao , Marc Zyngier , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Ben Gardon , Gavin Shan , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Page table walk is unnecessary in free_removed_table() being called from the stage-2 unmap path while PTEs on the table is empty. It can be fast-pathed by only initiating a walk if page_count() > 1 Original disussion can be found in: https://lore.kernel.org/kvmarm/ZHfWzX04GlcNngdU@linux.dev/ Suggested-by: Yu Zhao Suggested-by: Oliver Upton Signed-off-by: Chun-Tse Shao --- arch/arm64/kvm/hyp/pgtable.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index cc1af0286755..d8e570263388 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -1319,5 +1319,6 @@ void kvm_pgtable_stage2_free_removed(struct kvm_pgtable_mm_ops *mm_ops, void *pg .end = kvm_granule_size(level), }; - WARN_ON(__kvm_pgtable_walk(&data, mm_ops, ptep, level + 1)); + if (mm_ops->page_count(pgtable) > 1) + WARN_ON(__kvm_pgtable_walk(&data, mm_ops, ptep, level + 1)); } -- 2.41.0.162.gfafddb0af9-goog