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[91.12.101.198]) by smtp.gmail.com with ESMTPSA id g11sm1326042wrd.97.2021.08.17.00.14.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Aug 2021 00:14:33 -0700 (PDT) Subject: Re: [PATCH-for-6.1 v2] softmmu/physmem: fix wrong assertion in qemu_ram_alloc_internal() To: Peter Xu References: <20210805092350.31195-1-david@redhat.com> From: David Hildenbrand Organization: Red Hat Message-ID: <8812f9e2-3b3e-1bc9-2953-107e4c82880b@redhat.com> Date: Tue, 17 Aug 2021 09:14:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -71 X-Spam_score: -7.2 X-Spam_bar: ------- X-Spam_report: (-7.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.698, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-3.71, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , qemu-devel@nongnu.org, Peter Maydell Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 16.08.21 22:52, Peter Xu wrote: > On Thu, Aug 05, 2021 at 11:23:50AM +0200, David Hildenbrand wrote: >> When adding RAM_NORESERVE, we forgot to remove the old assertion when >> adding the updated one, most probably when reworking the patches or >> rebasing. We can easily crash QEMU by adding >> -object memory-backend-ram,id=mem0,size=500G,reserve=off >> to the QEMU cmdline: >> qemu-system-x86_64: ../softmmu/physmem.c:2146: qemu_ram_alloc_internal: >> Assertion `(ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC)) >> == 0' failed. >> >> Fix it by removing the old assertion. >> >> Fixes: 8dbe22c6868b ("memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap()") >> Reviewed-by: Peter Xu >> Reviewed-by: Philippe Mathieu-Daudé >> Tested-by: Philippe Mathieu-Daudé >> Cc: Paolo Bonzini >> Cc: Peter Xu >> Cc: Philippe Mathieu-Daudé >> Signed-off-by: David Hildenbrand >> --- >> >> v1 -> v2: >> - Added rbs >> - Tagged for 6.1 inclusion >> >> --- >> softmmu/physmem.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/softmmu/physmem.c b/softmmu/physmem.c >> index 3c1912a1a0..2e18947598 100644 >> --- a/softmmu/physmem.c >> +++ b/softmmu/physmem.c >> @@ -2143,7 +2143,6 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size, >> RAMBlock *new_block; >> Error *local_err = NULL; >> >> - assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC)) == 0); >> assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC | >> RAM_NORESERVE)) == 0); >> assert(!host ^ (ram_flags & RAM_PREALLOC)); >> -- >> 2.31.1 >> > > Today I just noticed this patch is still missing for 6.1. How many users are > there with reserve=off? Would it be worth rc4 or not? > Indeed, I forgot to follow up, thanks for bringing this up. Libvirt does not support virtio-mem yet and consequently doesn't support reserve=off yet. (there are use cases without virtio-mem, but I don't think anybody is using it yet) It's an easy way to crash QEMU, but we could also fix in the -stable tree instead. (most probably you and me should also be doing PULL requests for "Memory API", we'll have to discuss with Paolo) -- Thanks, David / dhildenb