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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 854D0F3D31B for ; Thu, 5 Mar 2026 16:08:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:MIME-Version: References:In-Reply-To:Subject:Cc:To:From:Message-ID:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=CNZjilY3nIi5iC0dvH7w23fZyKJ7Yu8EwufPGV0xT9E=; b=FKiMKjIzVc8prqWsP6Huouuyn/ 1Ef6VOZ8KqsXOFyT7aVVvNrfpYj5LlFvnl9IlgPcpbtOdgP8kR2kPmzWFTW8t+wl76Uf67fBlTbpP d8MqkFV3TcoJhAbBkdf3yB/+s/1IQCruDvh9t/fg2GCOWwNYp/IBOdBBKlPcZJvtnmh8zyz/rHHeb 0jAn0doK9bSgVfNvd6ekK06fXBl40EMt2wZlaRSwEPDu8/Cr5eSAx4kDSNKz9kmTw/se1+WK08AvR 4McMlr9pQvJ0CHWukuD6WCyvdkOzItcl6pg9mk95mdkYRwLf2An6oB3rFfnHyxc1XuSHhb1lY9zg2 KMDmMT0A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vyBF8-00000002BRN-023d; Thu, 05 Mar 2026 16:08:06 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vyBF4-00000002BQo-33uz for linux-arm-kernel@lists.infradead.org; Thu, 05 Mar 2026 16:08:05 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 15B6D42D9F; Thu, 5 Mar 2026 16:08:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DC960C116C6; Thu, 5 Mar 2026 16:08:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772726881; bh=SfeBnjWrPBoan1AGhscSpJ48+mNxFKjXxUAmNLQaKlM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=plFmZVgvxHa4iMJ6ycDhZGTJ4ci5QrVEZA+f2nBuM8Ub/F3oSmqQVjyWiSnGul7+I 5rlgHQpwh4+GslT0jEG4GH8CEOIaeP6MXIImNEsUg/Oh4Uxj6o6HG7ggVbH5MaKLfR Ht0Tmo+NshSBgQA/y82eP+KGXDeSqk5CYTBg8JmK370XElmIPsdQAfaD/zZ5r8bW7Q HbnNra3szKy1+pLCnjJZ9jvyLoojTQzaWBUS0SlcXZjiJj7st1vVMLa+3HTtoc4yVG mfY5Zo14I8u3beMHpMIzaVBFTeW2EUSMPTm988HlbGmQLFSn7yWtJ7u941Sa9TH10E NwP6NGy0rLqng== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1vyBF1-0000000GWOW-3IIk; Thu, 05 Mar 2026 16:07:59 +0000 Date: Thu, 05 Mar 2026 16:07:59 +0000 Message-ID: <86ms0m6yzk.wl-maz@kernel.org> From: Marc Zyngier To: Fuad Tabba Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, yangyicong@hisilicon.com, wangzhou1@hisilicon.com Subject: Re: [PATCH v1 2/2] KVM: arm64: Fix vma_shift staleness on nested hwpoison path In-Reply-To: <20260304162222.836152-3-tabba@google.com> References: <20260304162222.836152-1-tabba@google.com> <20260304162222.836152-3-tabba@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: tabba@google.com, kvm@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, yangyicong@hisilicon.com, wangzhou1@hisilicon.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260305_080804_044026_55AF7F51 X-CRM114-Status: GOOD ( 22.23 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Fuad, On Wed, 04 Mar 2026 16:22:22 +0000, Fuad Tabba wrote: > > When user_mem_abort() handles a nested stage-2 fault, it truncates > vma_pagesize to respect the guest's mapping size. However, the local > variable vma_shift is never updated to match this new size. > > If the underlying host page turns out to be hardware poisoned, > kvm_send_hwpoison_signal() is called with the original, larger > vma_shift instead of the actual mapping size. This signals incorrect > poison boundaries to userspace and breaks hugepage memory poison > containment for nested VMs. > > Update vma_shift to match the truncated vma_pagesize when operating > on behalf of a nested hypervisor. > > Fixes: fd276e71d1e7 ("KVM: arm64: nv: Handle shadow stage 2 page faults") > Signed-off-by: Fuad Tabba > --- > arch/arm64/kvm/mmu.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index e1d6a4f591a9..b08240e0cab1 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -1751,6 +1751,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > > force_pte = (max_map_size == PAGE_SIZE); > vma_pagesize = min_t(long, vma_pagesize, max_map_size); > + vma_shift = force_pte ? PAGE_SHIFT : __ffs(vma_pagesize); If force_pte is set, then we know that max_map_size == PAGE_SIZE. From there, vma_pagesize == PAGE_SIZE, since nothing can be smaller. Is there anything preventing us from having: vma_shift = __ffs(vma_pagesize); and be done with it? Thanks, M. -- Without deviation from the norm, progress is not possible.