From nobody Fri May 8 05:59:57 2026 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 77ACAC433EF for ; Tue, 10 May 2022 11:18:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240847AbiEJLWu (ORCPT ); Tue, 10 May 2022 07:22:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38226 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240833AbiEJLWa (ORCPT ); Tue, 10 May 2022 07:22:30 -0400 Received: from smtp-fw-2101.amazon.com (smtp-fw-2101.amazon.com [72.21.196.25]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B743C1868CB; Tue, 10 May 2022 04:18:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1652181513; x=1683717513; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=X4Q7oI+5uOvx0zCxStXfcdou0TUG9aiiGSJ0KXdxXIc=; b=lDGi//iFUUUiO81uAhwF6jt4bN6jD/M9ipmYBilk9saNf47gSZ7vHUjU QaSLRfJfIvPEcVRMDuIbCPVXHoKK3tFT48DLvFZnVX3p27XpQYmzIbdZ2 BkLwRR0uz1J3Ak6AhX6wVwQcbdDLcGSCcuNjqPfhkZGMi8aLCZmwN9sBf g=; X-IronPort-AV: E=Sophos;i="5.91,214,1647302400"; d="scan'208";a="196825572" Received: from iad12-co-svc-p1-lb1-vlan2.amazon.com (HELO email-inbound-relay-iad-1d-54a073b7.us-east-1.amazon.com) ([10.43.8.2]) by smtp-border-fw-2101.iad2.amazon.com with ESMTP; 10 May 2022 11:18:21 +0000 Received: from EX13MTAUWC001.ant.amazon.com (iad12-ws-svc-p26-lb9-vlan3.iad.amazon.com [10.40.163.38]) by email-inbound-relay-iad-1d-54a073b7.us-east-1.amazon.com (Postfix) with ESMTPS id 7186184C0F; Tue, 10 May 2022 11:18:19 +0000 (UTC) Received: from EX13D20UWC001.ant.amazon.com (10.43.162.244) by EX13MTAUWC001.ant.amazon.com (10.43.162.135) with Microsoft SMTP Server (TLS) id 15.0.1497.32; Tue, 10 May 2022 11:18:18 +0000 Received: from u79c5a0a55de558.ant.amazon.com (10.43.160.178) by EX13D20UWC001.ant.amazon.com (10.43.162.244) with Microsoft SMTP Server (TLS) id 15.0.1497.32; Tue, 10 May 2022 11:18:16 +0000 From: Alexander Graf To: CC: , , Christophe Leroy , Paul Mackerras , Benjamin Herrenschmidt , Michael Ellerman , Matt Evans , Subject: [PATCH v2] KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context() Date: Tue, 10 May 2022 13:18:09 +0200 Message-ID: <20220510111809.15987-1-graf@amazon.com> X-Mailer: git-send-email 2.28.0.394.ge197136389 MIME-Version: 1.0 X-Originating-IP: [10.43.160.178] X-ClientProxiedBy: EX13D16UWC003.ant.amazon.com (10.43.162.15) To EX13D20UWC001.ant.amazon.com (10.43.162.244) Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Commit 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C") moved the switch_mmu_context() to C. While in principle a good idea, it meant that the function now uses the stack. The stack is not accessible from real mode though. So to keep calling the function, let's turn on MSR_DR while we call it. That way, all pointer references to the stack are handled virtually. In addition, make sure to save/restore r12 in an SPRG, as it may get clobbered by the C function. Reported-by: Matt Evans Fixes: 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C") Signed-off-by: Alexander Graf Cc: stable@vger.kernel.org # v5.14+ --- v1 -> v2: - Save and restore R12, so that we don't touch volatile registers while calling into C. --- arch/powerpc/kvm/book3s_32_sr.S | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) diff --git a/arch/powerpc/kvm/book3s_32_sr.S b/arch/powerpc/kvm/book3s_32_s= r.S index e3ab9df6cf19..1ce13e3ab072 100644 --- a/arch/powerpc/kvm/book3s_32_sr.S +++ b/arch/powerpc/kvm/book3s_32_sr.S @@ -122,11 +122,27 @@ =20 /* 0x0 - 0xb */ =20 - /* 'current->mm' needs to be in r4 */ - tophys(r4, r2) - lwz r4, MM(r4) - tophys(r4, r4) - /* This only clobbers r0, r3, r4 and r5 */ + /* switch_mmu_context() clobbers r12, rescue it */ + SET_SCRATCH0(r12) + + /* switch_mmu_context() needs paging, let's enable it */ + mfmsr r9 + ori r11, r9, MSR_DR + mtmsr r11 + sync + + /* Calling switch_mmu_context(, current->mm, ); */ + lwz r4, MM(r2) bl switch_mmu_context =20 + /* Disable paging again */ + mfmsr r9 + li r6, MSR_DR + andc r9, r9, r6 + mtmsr r9 + sync + + /* restore r12 */ + GET_SCRATCH0(r12) + .endm --=20 2.28.0.394.ge197136389 Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B Sitz: Berlin Ust-ID: DE 289 237 879