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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 4E3DCC19F32 for ; Wed, 5 Mar 2025 12:50:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:MIME-Version: Message-ID:Date:References:In-Reply-To:Subject:Cc:To:From:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=gOoonUpRqPNjkNQ4QpxIoYxN7kGTACv6RWczqVQsTyA=; b=hYStfH/lBW/lQdn4Q4cWVJ2OTu 5mjnp2pJG4GuDe2jocVKyLdM3To0n7EOtILYpduERruauNDnsYKFh9I/SGRGcfcm8zO1QLnv4/At9 D7q+JxAV9tzrIPGsHb3bVYWwv/Fl+5puHXQynCYl9TAB3GtpG6v+CTv6v0o9UraqG/+AV2LbBgqCf B3cfZWRCuiieDzy1jYU6SdHMaRyVlLe53ydD51MAbt/yekYGnHl7SRSh1zhOp915LDqwvstWRWgsd zjs2+1CmLhIO3u9AX9LeMVrNeva10S4YFV7zP6lTGkjOpeHRniUgTmgzYNxwVVSVlrCWxVs62buVX XQpo8HCA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tpoCr-000000084zH-2RR6; Wed, 05 Mar 2025 12:50:37 +0000 Received: from galois.linutronix.de ([193.142.43.55]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tpoAr-000000084JQ-1ygV for linux-arm-kernel@lists.infradead.org; Wed, 05 Mar 2025 12:48:34 +0000 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1741178911; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=gOoonUpRqPNjkNQ4QpxIoYxN7kGTACv6RWczqVQsTyA=; b=Tw78+aD2h4Q9bJxkPET5ggTa0QOFh7B77Nmks06j5mAbVWcNFNVap3iMchhvravH5Q91wO apwsgFcp/8WB1IoHmJRjs+C9AZSgjweHdzptvazFiOEABNKOImRQBgejoMiRr9eQAjg89I csJ6iv+lD26eTKcCm5TNs9rBCDsI6UxsGMedLoPiDEr2GKAppOqZOlgz1bBK8YKwENu5LK 8q6ixkDUbCoRZGmMOcv8obqfEcB+s3Nnx6gzyFm9/JhX4JTWwYDFP3Wo9Q3nZYBhVZhDSl ND4dGQQDWXEKfsb3XbTw8AiwGnxLckKAY86xlUcypC0c1mSwmWNm78bDWl7bHw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1741178911; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=gOoonUpRqPNjkNQ4QpxIoYxN7kGTACv6RWczqVQsTyA=; b=fmJ56wTB1MtRovyNVQEoH5tvswtVy3ruIssA+yqjmGNDv4QDUm3QYMDYGjoIwmnB0Uf4Zp 2Kuaj9lNmt0kEXAQ== To: Valentin Schneider , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org Cc: Mark Rutland , Mike Galbraith , Catalin Marinas , Will Deacon , Peter Collingbourne , Neeraj Upadhyay , Thiago Jung Bauermann , Mark Brown , Kristina Martsenko , Sebastian Andrzej Siewior , Petr Tesarik , Jinjie Ruan , Juri Lelli , Phil Auld Subject: Re: [PATCH 1/1] arm64: enable PREEMPT_LAZY In-Reply-To: <20250305104925.189198-2-vschneid@redhat.com> References: <20250305104925.189198-1-vschneid@redhat.com> <20250305104925.189198-2-vschneid@redhat.com> Date: Wed, 05 Mar 2025 13:48:30 +0100 Message-ID: <87cyev63tt.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250305_044833_651445_6DB99A88 X-CRM114-Status: GOOD ( 13.54 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Mar 05 2025 at 11:49, Valentin Schneider wrote: > From: Mark Rutland > > For an architecture to enable CONFIG_ARCH_HAS_RESCHED_LAZY, two things are > required: > 1) Adding a TIF_NEED_RESCHED_LAZY flag definition > 2) Checking for TIF_NEED_RESCHED_LAZY in the appropriate locations > > 2) is handled in a generic manner by CONFIG_GENERIC_ENTRY, which isn't > (yet) implemented for arm64. However, outside of core scheduler code, > TIF_NEED_RESCHED_LAZY only needs to be checked on a kernel exit, meaning: > o return/entry to userspace. > o return/entry to guest. > > The return/entry to a guest is all handled by xfer_to_guest_mode_handle_work() > which already does the right thing, so it can be left as-is. > > arm64 doesn't use common entry's exit_to_user_mode_prepare(), so update its > return to user path to check for TIF_NEED_RESCHED_LAZY and call into > schedule() accordingly. > > Link: https://lore.kernel.org/linux-rt-users/20241216190451.1c61977c@mordecai.tesarici.cz/ > Link: https://lore.kernel.org/all/xhsmh4j0fl0p3.mognet@vschneid-thinkpadt14sgen2i.remote.csb/ > Signed-off-by: Mark Rutland > [testdrive, _TIF_WORK_MASK fixlet and changelog.] > Signed-off-by: Mike Galbraith > [Another round of testing; changelog faff] > Signed-off-by: Valentin Schneider Reviewed-by: Thomas Gleixner