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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id w15-20020a63b74f000000b003f26c2f583asm6842111pgt.61.2022.05.24.12.35.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 May 2022 12:35:56 -0700 (PDT) Date: Tue, 24 May 2022 19:35:52 +0000 From: Sean Christopherson To: zhenwei pi Cc: akpm@linux-foundation.org, naoya.horiguchi@nec.com, mst@redhat.com, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jasowang@redhat.com, virtualization@lists.linux-foundation.org, pbonzini@redhat.com, peterx@redhat.com, qemu-devel@nongnu.org Subject: Re: [PATCH 3/3] virtio_balloon: Introduce memory recover Message-ID: References: <20220520070648.1794132-1-pizhenwei@bytedance.com> <20220520070648.1794132-4-pizhenwei@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220520070648.1794132-4-pizhenwei@bytedance.com> X-Rspamd-Queue-Id: BCA7240023 X-Stat-Signature: agmu915x86ykpqeu5rkw9peid7qu47ys Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=Wq7LLslO; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf17.hostedemail.com: domain of seanjc@google.com designates 209.85.214.176 as permitted sender) smtp.mailfrom=seanjc@google.com X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1653420928-114021 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, May 20, 2022, zhenwei pi wrote: > @@ -59,6 +60,12 @@ enum virtio_balloon_config_read { > VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0, > }; > > +/* the request body to commucate with host side */ > +struct __virtio_balloon_recover { > + struct virtio_balloon_recover vbr; > + __virtio32 pfns[VIRTIO_BALLOON_PAGES_PER_PAGE]; I assume this is copied from virtio_balloon.pfns, which also uses __virtio32, but isn't that horribly broken? PFNs are 'unsigned long', i.e. 64 bits on 64-bit kernels. x86-64 at least most definitely generates 64-bit PFNs. Unless there's magic I'm missing, page_to_balloon_pfn() will truncate PFNs and feed the host bad info. > @@ -494,6 +511,198 @@ static void update_balloon_size_func(struct work_struct *work) > queue_work(system_freezable_wq, work); > } > > +/* > + * virtballoon_memory_failure - notified by memory failure, try to fix the > + * corrupted page. > + * The memory failure notifier is designed to call back when the kernel handled > + * successfully only, WARN_ON_ONCE on the unlikely condition to find out any > + * error(memory error handling is a best effort, not 100% coverd). > + */ > +static int virtballoon_memory_failure(struct notifier_block *notifier, > + unsigned long pfn, void *parm) > +{ > + struct virtio_balloon *vb = container_of(notifier, struct virtio_balloon, > + memory_failure_nb); > + struct page *page; > + struct __virtio_balloon_recover *out_vbr; > + struct scatterlist sg; > + unsigned long flags; > + int err; > + > + page = pfn_to_online_page(pfn); > + if (WARN_ON_ONCE(!page)) > + return NOTIFY_DONE; > + > + if (PageHuge(page)) > + return NOTIFY_DONE; > + > + if (WARN_ON_ONCE(!PageHWPoison(page))) > + return NOTIFY_DONE; > + > + if (WARN_ON_ONCE(page_count(page) != 1)) > + return NOTIFY_DONE; > + > + get_page(page); /* balloon reference */ > + > + out_vbr = kzalloc(sizeof(*out_vbr), GFP_KERNEL); > + if (WARN_ON_ONCE(!out_vbr)) > + return NOTIFY_BAD; Not that it truly matters, but won't failure at this point leak the poisoned page?