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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 E1AE7C742BA for ; Fri, 12 Jul 2019 13:12:53 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 729932080A for ; Fri, 12 Jul 2019 13:12:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 729932080A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 45lYJ268lkzDqyB for ; Fri, 12 Jul 2019 23:12:50 +1000 (AEST) Received: from ozlabs.org (bilbo.ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 45lYD00VYYzDqpg for ; Fri, 12 Jul 2019 23:09:20 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 45lYCz49PFz9s3l; Fri, 12 Jul 2019 23:09:19 +1000 (AEST) From: Michael Ellerman To: Suraj Jitindar Singh , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH] powerpc: mm: Limit rma_size to 1TB when running without HV mode In-Reply-To: <20190710052018.14628-1-sjitindarsingh@gmail.com> References: <20190710052018.14628-1-sjitindarsingh@gmail.com> Date: Fri, 12 Jul 2019 23:09:18 +1000 Message-ID: <87o91ze6wx.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: sjitindarsingh@gmail.com, kvm-ppc@vger.kernel.org, david@gibson.dropbear.id.au Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Suraj Jitindar Singh writes: > The virtual real mode addressing (VRMA) mechanism is used when a > partition is using HPT (Hash Page Table) translation and performs > real mode accesses (MSR[IR|DR] = 0) in non-hypervisor mode. In this > mode effective address bits 0:23 are treated as zero (i.e. the access > is aliased to 0) and the access is performed using an implicit 1TB SLB > entry. > > The size of the RMA (Real Memory Area) is communicated to the guest as > the size of the first memory region in the device tree. And because of > the mechanism described above can be expected to not exceed 1TB. In the > event that the host erroneously represents the RMA as being larger than > 1TB, guest accesses in real mode to memory addresses above 1TB will be > aliased down to below 1TB. This means that a memory access performed in > real mode may differ to one performed in virtual mode for the same memory > address, which would likely have unintended consequences. > > To avoid this outcome have the guest explicitly limit the size of the > RMA to the current maximum, which is 1TB. This means that even if the > first memory block is larger than 1TB, only the first 1TB should be > accessed in real mode. > > Signed-off-by: Suraj Jitindar Singh I added: Fixes: c3ab300ea555 ("powerpc: Add POWER9 cputable entry") Cc: stable@vger.kernel.org # v4.6+ Which is not exactly correct, but probably good enough? cheers > diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c > index 28ced26f2a00..4d0e2cce9cd5 100644 > --- a/arch/powerpc/mm/book3s64/hash_utils.c > +++ b/arch/powerpc/mm/book3s64/hash_utils.c > @@ -1901,11 +1901,19 @@ void hash__setup_initial_memory_limit(phys_addr_t first_memblock_base, > * > * For guests on platforms before POWER9, we clamp the it limit to 1G > * to avoid some funky things such as RTAS bugs etc... > + * On POWER9 we limit to 1TB in case the host erroneously told us that > + * the RMA was >1TB. Effective address bits 0:23 are treated as zero > + * (meaning the access is aliased to zero i.e. addr = addr % 1TB) > + * for virtual real mode addressing and so it doesn't make sense to > + * have an area larger than 1TB as it can't be addressed. > */ > if (!early_cpu_has_feature(CPU_FTR_HVMODE)) { > ppc64_rma_size = first_memblock_size; > if (!early_cpu_has_feature(CPU_FTR_ARCH_300)) > ppc64_rma_size = min_t(u64, ppc64_rma_size, 0x40000000); > + else > + ppc64_rma_size = min_t(u64, ppc64_rma_size, > + 1UL << SID_SHIFT_1T); > > /* Finally limit subsequent allocations */ > memblock_set_current_limit(ppc64_rma_size); > -- > 2.13.6