From patchwork Sun Apr 13 12:59:37 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 14049320 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.gnu.org (lists.gnu.org [209.51.188.17]) (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 14F59C369B1 for ; Sun, 13 Apr 2025 13:00:55 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1u3wwN-0000vf-9v; Sun, 13 Apr 2025 09:00:03 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1u3wwB-0000ry-BW; Sun, 13 Apr 2025 08:59:51 -0400 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1u3ww9-0007v3-MB; Sun, 13 Apr 2025 08:59:51 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 5BFD7116A4F; Sun, 13 Apr 2025 15:57:57 +0300 (MSK) Received: from gandalf.tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with ESMTP id E9D451EEE7C; Sun, 13 Apr 2025 15:59:37 +0300 (MSK) Received: by gandalf.tls.msk.ru (Postfix, from userid 1000) id D4EF858527; Sun, 13 Apr 2025 15:59:37 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: Richard Henderson , qemu-trivial@nongnu.org, Michael Tokarev Subject: [PULL 3/3] docs: Document removal of 64-bit on 32-bit emulation Date: Sun, 13 Apr 2025 15:59:37 +0300 Message-Id: <20250413125937.2448971-4-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250413125937.2448971-1-mjt@tls.msk.ru> References: <20250413125937.2448971-1-mjt@tls.msk.ru> MIME-Version: 1.0 Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Richard Henderson With acce728cbc6c we disallowed configuring 64-bit guests on 32-bit hosts, but forgot to document that in removed-features. Signed-off-by: Richard Henderson Reviewed-by: Michael Tokarev Signed-off-by: Michael Tokarev --- docs/about/removed-features.rst | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/docs/about/removed-features.rst b/docs/about/removed-features.rst index 2527a91795..790a5e481c 100644 --- a/docs/about/removed-features.rst +++ b/docs/about/removed-features.rst @@ -858,6 +858,15 @@ QEMU. Since all recent x86 hardware from the past >10 years is capable of the 64-bit x86 extensions, a corresponding 64-bit OS should be used instead. +32-bit hosts for 64-bit guests (removed in 10.0) +'''''''''''''''''''''''''''''''''''''''''''''''' + +In general, 32-bit hosts cannot support the memory space or atomicity +requirements of 64-bit guests. Prior to 10.0, QEMU attempted to +work around the atomicity issues in system mode by running all vCPUs +in a single thread context; in user mode atomicity was simply broken. +From 10.0, QEMU has disabled configuration of 64-bit guests on 32-bit hosts. + Guest Emulator ISAs -------------------