From patchwork Mon Apr 19 12:01:39 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Ellerman X-Patchwork-Id: 1467922 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=kvm-ppc-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=ellerman.id.au header.i=@ellerman.id.au header.a=rsa-sha256 header.s=201909 header.b=CHYfao/W; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4FP55T5KJvz9tkw for ; Mon, 19 Apr 2021 22:01:49 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238973AbhDSMCS (ORCPT ); Mon, 19 Apr 2021 08:02:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41406 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238936AbhDSMCR (ORCPT ); Mon, 19 Apr 2021 08:02:17 -0400 Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 18BA8C06174A for ; Mon, 19 Apr 2021 05:01:48 -0700 (PDT) Received: by ozlabs.org (Postfix, from userid 1034) id 4FP55P16ZXz9tlB; Mon, 19 Apr 2021 22:01:45 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ellerman.id.au; s=201909; t=1618833705; bh=Zk/xJ1WJy0d9ipj/dDcSW2umjEfymDbl/vAyn+8IIZo=; h=From:To:Cc:Subject:Date:From; b=CHYfao/WngBzEEa4m3SGxvVoMqUc9VaU3ctho9ZrQZ6cwEoGVa0X5iakv2lbLnMdc jSfUThmcH4vusHrIgNSiUXB4fd/SZlgSuu5NkGueWyVPKb/wvRf2yfHXaz6BuUTP0O jkjOJe11nen+oREvSAxaViniH2T2KIb59dQHrjqOQ9HhD3f/uxyrk0UInhIvXfK2JF yinrDOL3RUlwLf6mmva+hKteMi5hd3YMMMkR6IHqMotTWEGGamvhp/vyMtCDJ48ZFZ 63auToQ8Axi0QCqBDJuKdw2ly0FVMXEdharvCUYinIR2rkvbTfDS7V9EoPckici/Df +XVgwNo4FfMrw== From: Michael Ellerman To: linuxppc-dev@lists.ozlabs.org Cc: aneesh.kumar@linux.ibm.com, kvm-ppc@vger.kernel.org Subject: [PATCH] powerpc/kvm: Fix PR KVM with KUAP/MEM_KEYS enabled Date: Mon, 19 Apr 2021 22:01:39 +1000 Message-Id: <20210419120139.1455937-1-mpe@ellerman.id.au> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm-ppc@vger.kernel.org The changes to add KUAP support with the hash MMU broke booting of KVM PR guests. The symptom is no visible progress of the guest, or possibly just "SLOF" being printed to the qemu console. Host code is still executing, but breaking into xmon might show a stack trace such as: __might_fault+0x84/0xe0 (unreliable) kvm_read_guest+0x1c8/0x2f0 [kvm] kvmppc_ld+0x1b8/0x2d0 [kvm] kvmppc_load_last_inst+0x50/0xa0 [kvm] kvmppc_exit_pr_progint+0x178/0x220 [kvm_pr] kvmppc_handle_exit_pr+0x31c/0xe30 [kvm_pr] after_sprg3_load+0x80/0x90 [kvm_pr] kvmppc_vcpu_run_pr+0x104/0x260 [kvm_pr] kvmppc_vcpu_run+0x34/0x48 [kvm] kvm_arch_vcpu_ioctl_run+0x340/0x450 [kvm] kvm_vcpu_ioctl+0x2ac/0x8c0 [kvm] sys_ioctl+0x320/0x1060 system_call_exception+0x160/0x270 system_call_common+0xf0/0x27c Bisect points to commit b2ff33a10c8b ("powerpc/book3s64/hash/kuap: Enable kuap on hash"), but that's just the commit that enabled KUAP with hash and made the bug visible. The root cause seems to be that KVM PR is creating kernel mappings that don't use the correct key, since we switched to using key 3. We have a helper for adding the right key value, however it's designed to take a pteflags variable, which the KVM code doesn't have. But we can make it work by passing 0 for the pteflags, and tell it explicitly that it should use the kernel key. With that changed guests boot successfully. Fixes: d94b827e89dc ("powerpc/book3s64/kuap: Use Key 3 for kernel mapping with hash translation") Cc: stable@vger.kernel.org # v5.11+ Signed-off-by: Michael Ellerman --- arch/powerpc/kvm/book3s_64_mmu_host.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/powerpc/kvm/book3s_64_mmu_host.c b/arch/powerpc/kvm/book3s_64_mmu_host.c index e452158a18d7..5ac66be1cb3c 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_host.c +++ b/arch/powerpc/kvm/book3s_64_mmu_host.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -133,6 +134,7 @@ int kvmppc_mmu_map_page(struct kvm_vcpu *vcpu, struct kvmppc_pte *orig_pte, else kvmppc_mmu_flush_icache(pfn); + rflags |= pte_to_hpte_pkey_bits(0, HPTE_USE_KERNEL_KEY); rflags = (rflags & ~HPTE_R_WIMG) | orig_pte->wimg; /*