From patchwork Mon Feb 21 10:22:05 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Julien Grall X-Patchwork-Id: 12753370 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 lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0321FC4332F for ; Mon, 21 Feb 2022 10:22:41 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.275992.472053 (Exim 4.92) (envelope-from ) id 1nM5pu-0005Wb-Vb; Mon, 21 Feb 2022 10:22:30 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 275992.472053; Mon, 21 Feb 2022 10:22:30 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1nM5pu-0005UD-C0; Mon, 21 Feb 2022 10:22:30 +0000 Received: by outflank-mailman (input) for mailman id 275992; Mon, 21 Feb 2022 10:22:29 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1nM5pt-0005K5-3e for xen-devel@lists.xenproject.org; Mon, 21 Feb 2022 10:22:29 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1nM5ps-0002Bb-VA; Mon, 21 Feb 2022 10:22:28 +0000 Received: from 54-240-197-232.amazon.com ([54.240.197.232] helo=dev-dsk-jgrall-1b-035652ec.eu-west-1.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1nM5ps-00070b-Nq; Mon, 21 Feb 2022 10:22:28 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:MIME-Version:References: In-Reply-To:Message-Id:Date:Subject:Cc:To:From; bh=0n6etsYqo9bTpW5hKB66bUfArotdLsp5P4nlJNvCktk=; b=hpgsGAWjKmB3nCSgB72nz6fMpj r5/GlFDET7YiB2drOVybCDihBpbWM3SlDyrUqXpruffX2XpjwkPE6cv4hWqvOVQCUIxsTt7LGN+38 362aFG77G5lHwua6lUDhpNwJ3AxG30RyARIlXYyQuB4XK18ZGjEAJ6805oSnkYXwQdY8=; From: Julien Grall To: xen-devel@lists.xenproject.org Cc: julien@xen.org, Julien Grall , Stefano Stabellini , Bertrand Marquis , Volodymyr Babchuk Subject: [PATCH v3 06/19] xen/arm: mm: Avoid flushing the TLBs when mapping are inserted Date: Mon, 21 Feb 2022 10:22:05 +0000 Message-Id: <20220221102218.33785-7-julien@xen.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220221102218.33785-1-julien@xen.org> References: <20220221102218.33785-1-julien@xen.org> MIME-Version: 1.0 From: Julien Grall Currently, the function xen_pt_update() will flush the TLBs even when the mappings are inserted. This is a bit wasteful because we don't allow mapping replacement. Even if we were, the flush would need to happen earlier because mapping replacement should use Break-Before-Make when updating the entry. A single call to xen_pt_update() can perform a single action. IOW, it is not possible to, for instance, mix inserting and removing mappings. Therefore, we can use `flags` to determine what action is performed. This change will be particularly help to limit the impact of switching boot time mapping to use xen_pt_update(). Signed-off-by: Julien Grall --- Changes in v2: - New patch --- xen/arch/arm/mm.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c index fd16c1541ce2..7b4b9de8693e 100644 --- a/xen/arch/arm/mm.c +++ b/xen/arch/arm/mm.c @@ -1104,7 +1104,13 @@ static bool xen_pt_check_entry(lpae_t entry, mfn_t mfn, unsigned int level, /* We should be here with a valid MFN. */ ASSERT(!mfn_eq(mfn, INVALID_MFN)); - /* We don't allow replacing any valid entry. */ + /* + * We don't allow replacing any valid entry. + * + * Note that the function xen_pt_update() relies on this + * assumption and will skip the TLB flush. The function will need + * to be updated if the check is relaxed. + */ if ( lpae_is_valid(entry) ) { if ( lpae_is_mapping(entry, level) ) @@ -1417,11 +1423,16 @@ static int xen_pt_update(unsigned long virt, } /* - * Flush the TLBs even in case of failure because we may have + * The TLBs flush can be safely skipped when a mapping is inserted + * as we don't allow mapping replacement (see xen_pt_check_entry()). + * + * For all the other cases, the TLBs will be flushed unconditionally + * even if the mapping has failed. This is because we may have * partially modified the PT. This will prevent any unexpected * behavior afterwards. */ - flush_xen_tlb_range_va(virt, PAGE_SIZE * nr_mfns); + if ( !(flags & _PAGE_PRESENT) || mfn_eq(mfn, INVALID_MFN) ) + flush_xen_tlb_range_va(virt, PAGE_SIZE * nr_mfns); spin_unlock(&xen_pt_lock);