From nobody Tue Feb 10 07:23:57 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1694611216121632.3683836886964; Wed, 13 Sep 2023 06:20:16 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qgPll-0007fI-FG; Wed, 13 Sep 2023 09:19:01 -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 1qgPlj-0007e2-Ga; Wed, 13 Sep 2023 09:18:59 -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 1qgPlg-0003Wq-Sy; Wed, 13 Sep 2023 09:18:59 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 9DA9521768; Wed, 13 Sep 2023 16:18:09 +0300 (MSK) Received: from tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with SMTP id 7BE9B27C8B; Wed, 13 Sep 2023 16:18:03 +0300 (MSK) Received: (nullmailer pid 4073307 invoked by uid 1000); Wed, 13 Sep 2023 13:18:00 -0000 From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Colton Lewis , Andrew Jones , Richard Henderson , Peter Maydell , Michael Tokarev Subject: [Stable-8.0.5 57/66] arm64: Restore trapless ptimer access Date: Wed, 13 Sep 2023 16:17:38 +0300 Message-Id: <20230913131757.4073200-14-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; 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, 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1694611217955100003 Content-Type: text/plain; charset="utf-8" From: Colton Lewis Due to recent KVM changes, QEMU is setting a ptimer offset resulting in unintended trap and emulate access and a consequent performance hit. Filter out the PTIMER_CNT register to restore trapless ptimer access. Quoting Andrew Jones: Simply reading the CNT register and writing back the same value is enough to set an offset, since the timer will have certainly moved past whatever value was read by the time it's written. QEMU frequently saves and restores all registers in the get-reg-list array, unless they've been explicitly filtered out (with Linux commit 680232a94c12, KVM_REG_ARM_PTIMER_CNT is now in the array). So, to restore trapless ptimer accesses, we need a QEMU patch to filter out the register. See https://lore.kernel.org/kvmarm/gsntttsonus5.fsf@coltonlewis-kvm.c.googlers.= com/T/#m0770023762a821db2a3f0dd0a7dc6aa54e0d0da9 for additional context. Cc: qemu-stable@nongnu.org Signed-off-by: Andrew Jones Signed-off-by: Colton Lewis Reviewed-by: Richard Henderson Tested-by: Colton Lewis Message-id: 20230831190052.129045-1-coltonlewis@google.com Signed-off-by: Peter Maydell (cherry picked from commit 682814e2a3c883b27f24b9e7cab47313c49acbd4) Signed-off-by: Michael Tokarev diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c index 810db33ccb..ed85bcfb5c 100644 --- a/target/arm/kvm64.c +++ b/target/arm/kvm64.c @@ -950,6 +950,7 @@ typedef struct CPRegStateLevel { */ static const CPRegStateLevel non_runtime_cpregs[] =3D { { KVM_REG_ARM_TIMER_CNT, KVM_PUT_FULL_STATE }, + { KVM_REG_ARM_PTIMER_CNT, KVM_PUT_FULL_STATE }, }; =20 int kvm_arm_cpreg_level(uint64_t regidx) --=20 2.39.2