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 X-Spam-Level: X-Spam-Status: No, score=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6495C43465 for ; Fri, 18 Sep 2020 02:55:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9BCCD2078D for ; Fri, 18 Sep 2020 02:55:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600397736; bh=SPERwlclIXQwTDhY9S9VzGMn42+SabgQHJDdP2nrnVQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=0xSuUDI1K/lWiTCU1KbqLqbXn5fE7bfEV3PiRCJVAJzmr96/CoWwgxcGuZAIrV1Ip DjZhjf7FpDVPmeDSr6PDx8PXGyv3Xb9sCMx914mQwxJHVarXyVBuG7DK/7awY5YwUJ UzOTlpBukh2aQZrGSdrTb0uU2vr1tFMQ+1W9JO+I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730077AbgIRCzf (ORCPT ); Thu, 17 Sep 2020 22:55:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:57222 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727855AbgIRCHI (ORCPT ); Thu, 17 Sep 2020 22:07:08 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7380F23A31; Fri, 18 Sep 2020 02:07:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600394825; bh=SPERwlclIXQwTDhY9S9VzGMn42+SabgQHJDdP2nrnVQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rO7WPuTZ/yUzvg9shwPlE0akOMvDAHC4/R1DGcEMDLKFfYVc6hvHJ2y7HIv1rFh7l 1n7s+70jVctX0/NoThT8uncUrTZdJ8C5mQ1svngMo4fNhMyY2GDoLeXo1cRpncqm3O LMziZvv18gnNC+a0IyQHYvA1dHhDfycxu4/+3ZDs= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Paul Mackerras , Sasha Levin , kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: [PATCH AUTOSEL 5.4 290/330] KVM: PPC: Book3S HV: Close race with page faults around memslot flushes Date: Thu, 17 Sep 2020 22:00:30 -0400 Message-Id: <20200918020110.2063155-290-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200918020110.2063155-1-sashal@kernel.org> References: <20200918020110.2063155-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Paul Mackerras [ Upstream commit 11362b1befeadaae4d159a8cddcdaf6b8afe08f9 ] There is a potential race condition between hypervisor page faults and flushing a memslot. It is possible for a page fault to read the memslot before a memslot is updated and then write a PTE to the partition-scoped page tables after kvmppc_radix_flush_memslot has completed. (Note that this race has never been explicitly observed.) To close this race, it is sufficient to increment the MMU sequence number while the kvm->mmu_lock is held. That will cause mmu_notifier_retry() to return true, and the page fault will then return to the guest without inserting a PTE. Signed-off-by: Paul Mackerras Signed-off-by: Sasha Levin --- arch/powerpc/kvm/book3s_64_mmu_radix.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c index da8375437d161..9d73448354698 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c @@ -1104,6 +1104,11 @@ void kvmppc_radix_flush_memslot(struct kvm *kvm, kvm->arch.lpid); gpa += PAGE_SIZE; } + /* + * Increase the mmu notifier sequence number to prevent any page + * fault that read the memslot earlier from writing a PTE. + */ + kvm->mmu_notifier_seq++; spin_unlock(&kvm->mmu_lock); } -- 2.25.1