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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-30f0bbd223esm25620535eec.21.2026.07.03.16.36.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 03 Jul 2026 16:36:25 -0700 (PDT) Message-ID: <77d7e748-25d0-4090-8954-ab96bb37f223@redhat.com> Date: Sat, 4 Jul 2026 09:36:13 +1000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v14 29/44] arm64: RMI: Runtime faulting of memory To: Lorenzo Pieralisi Cc: Suzuki K Poulose , Steven Price , kvm@vger.kernel.org, kvmarm@lists.linux.dev, Catalin Marinas , Marc Zyngier , Will Deacon , James Morse , Oliver Upton , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev, Ganapatrao Kulkarni , Shanker Donthineni , Alper Gun , "Aneesh Kumar K . V" , Emi Kisanuki , Vishal Annapurve , WeiLin.Chang@arm.com, Lorenzo.Pieralisi2@arm.com References: <1e39094f-7fa3-4ef1-be54-53d7a8643506@redhat.com> <98d2a0f3-b831-466a-8212-5bcf97ad9d8b@arm.com> <8da87878-2a5d-478a-a280-60dbed7ad1b9@redhat.com> <9482dfbc-4d96-47ba-a615-f4ba0bda833f@arm.com> <8f81ed99-c53a-4196-baa2-adea9239a000@redhat.com> <901398bb-ed6c-4997-b3cd-ce2829b09c87@redhat.com> From: Gavin Shan In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: lCzxF0s_tvPKGdyySeqpo75fXawTw6_eqm9-Q9TAKAM_1783121787 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260703_163632_655982_094C51E8 X-CRM114-Status: GOOD ( 40.05 ) 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 On 7/1/26 11:58 PM, Lorenzo Pieralisi wrote: > On Sun, Jun 28, 2026 at 08:33:01PM +1000, Gavin Shan wrote: >> On 6/27/26 2:44 AM, Lorenzo Pieralisi wrote: >>> On Fri, Jun 26, 2026 at 09:43:03PM +1000, Gavin Shan wrote: >>>> On 6/26/26 6:47 PM, Suzuki K Poulose wrote: >>>>> On 26/06/2026 08:43, Gavin Shan wrote: >>>>>> On 6/26/26 1:58 AM, Suzuki K Poulose wrote: >>>>>>> On 25/06/2026 14:53, Gavin Shan wrote: >>>>>>>> On 6/6/26 12:35 AM, Lorenzo Pieralisi wrote: >>>>>>>>> On Fri, Jun 05, 2026 at 06:11:11PM +1000, Gavin Shan wrote: >>>>>>>>>> On 6/5/26 5:28 PM, Lorenzo Pieralisi wrote: >>>>>>>>>>> On Fri, Jun 05, 2026 at 04:23:15PM +1000, Gavin Shan wrote: >>>>>> >>>>>> [...] >>>>>> >>>>>>>>>> >>>>>>>>>> I tried to rebase Jean's latest QEMU series [1] to upstream QEMU, and found >>>>>>>>>> that memory slots backed by THP are broken. With THP disabled on the host and >>>>>>>>>> other fixes (mentioned in my prevous replies) applied on the top of this (v14) >>>>>>>>>> series, I'm able to boot a realm guest with rebased QEMU series [2], plus more >>>>>>>>>> fxies on the top. >>>>>>>>>> >>>>>>>>>> [1] https://git.codelinaro.org/linaro/dcap/qemu.git  (branch: cca/ latest) >>>>>>>>>> [2] https://git.qemu.org/git/qemu.git                (branch: cca/ gavin) >>>>>>>>>> >>>>>>>>>> Lorenzo, You may be saying there is someone making QEMU to support ARM/CCA? >>>>>>>>> >>>>>>>>> Mathieu and I are working on that yes and with Steven/Suzuki to fix the THP >>>>>>>>> issues you pointed out above. >>>>>>>>> >>>>>>>>>> If so, I'm not sure if there is a QEMU repository for me to try? >>>>>>>>> >>>>>>>>> We should be able to submit patches by end of June - we shall let you know >>>>>>>>> whether we can make something available earlier. >>>>>>>>> >>>>>>>> >>>>>>>> Not sure if there are other known issues in this series. It seems the stage2 >>>>>>>> page fault handling on the shared space isn't working well. In my test, the >>>>>>>> vring (struct vring_desc) of virtio-net-pci is updated by the guest, and the >>>>>>>> data isn't seen by QEMU, I'm suspecting if the host-page-frame-number is properly >>>>>>>> resolved in the s2 page fault handler for shared (unprotected) space. >>>>>>>> >>>>>>>> - I rebased Jean's latest qemu branch to the upstream qemu; >>>>>>>> >>>>>>>> - On the host, which is emulated by qemu/tcg, the THP (transparent huge page) is >>>>>>>>    disabled. >>>>>>>> >>>>>>>> - On the guest, I can see the virtio vring (struct vring_desc) is updated. The >>>>>>>>    S1 page-table entry looks correct because the corresponding physical address >>>>>>>>    0x10046880000 is a sane shared (unprotected) space address. >>>>>>>> >>>>>>>>    [   52.094143] software IO TLB: Memory encryption is active and system is using DMA bounce buffers >>>>>>>>    [   52.289746] virtqueue_add_desc_split: desc[0]@0xffff000006880000, [00000100b983f000  00000640  0002  0001] >>>>>>>>    [   52.432150] PTE 0x00e8010046880707 at address 0xffff000006880000 >>>>>>>> >>>>>>>> - On the host, the s2 page-table-entry is unmapped due to attribute transition (private -> shared). >>>>>>>>    A subsequent S2 page fault is raised against the adress and the s2 page-table-entry is built. >>>>>>>> >>>>>>>>    [  109.259077] ====> realm_unmap_shared_range: tracked_unprot_addr=0x10046880000 >>>>>>>>    [  109.260249] realm_unmap_shared_range: unmapped shared range at 0x10046880000 >>>>>>>>    [  109.317786] realm_unmap_shared_range: unmapped shared range at 0x10046880000 >>>>>>>>    [  109.629939] ====> kvm_handle_guest_abort: fault_ipa=0x10046880000, esr=0x92000007 >>>>>>>>    [  109.630245] realm_map_non_secure: ipa=0x10046880000, pfn=0xb8b59, size=0x1000, prot=0xf >>>>>>>>    [  109.630331] realm_map_non_secure: ipa=0x10046880000, ipa_top=0x10046881000, flags=0x1e0001, range_desc=0xb8b59004 >>>>>>> >>>>>>> Are you able to correlate the order of the transitions and the Guest >>>>>>> access with RMM log ? We haven't seen this from our end. We are aware >>>>>>> of permission fault issues with Unprotected IPA when backing the memslot >>>>>>> with MAP_PRIVATE areas. But this looks different. >>>>>>> >>>>>>> Lorenzo, have you run into this ? >>>>>>> >>>>>> >>>>>> It's hard to correlate the order since the logs are collected from two separate >>>>>> consoles. For the write permission, I add code to the host where the permission >>>>>> is always added for all s2 page faults in the shared space. Otherwise, qemu can >>>>>> be killed by -EFAULT or similar error. >>>>> >>>>> This is the problem. We can't add WRITE permission by default. I believe >>>>> you may have MAP_PRIVATE mapping and it has to be mapped as READ only >>>>> and on a permission fault, we replace it with a writable page. By >>>>> overriding the WRITE permission, you let the guest write to a page >>>>> that may not be seen by the VMM. >>>>> >>>>> We identified this as a bug in the KVM driver in this series (reported >>>>> by Lorenzo) and there is a corresponding tf-RMM change that is required >>>>> to get this working. So, please could you wait until the next series >>>>> when this will be addressed ? Or you could switch to using MAP_SHARED >>>>> for the "shared" memory in the memslot. >>>>> >>>> >>>> Exactly. the syntax for MAP_PRIVATE is broken if the write permission is >>>> enforced for a read fault in the shared space. In my case, the host page can >>>> be the zero page and eventually multiple s2 page-table entries (for multiple >>>> unprotected or shared pages) point to the zero page. It's why clearing the >>>> 3rd queue (Ctrl queue) also clears the first queue (Rx queue) in my case. >>>> >>>> Yes, this issue can be avoid by using a shared memory backend in qemu, something >>>> like below. With this, I'm able to see virtio-net-pci starts to work... >>>> >>>> -object memory-backend-ram,id=mem0,size=2G,share=yes >>> >>> Yes, as Suzuki said that's what we have been fixing. QEmu patches >>> will be on the mailing lists very shortly - the KVM/tf-RMM fixes >>> to make MAP_PRIVATE work will be included in the next posting. >>> >>> Feel free to drop your QEmu command line so that I can give it >>> a shot and check whether the fixes solve the problem you hit >>> (I think so because that's precisely the kind of issue I got >>> into when I started debugging THP/MAP_PRIVATE but it is better >>> to check). >>> >> >> The virtio-net-pci doesn't work with the following command lines. The guest >> kernel image is built from upstream kernel (v7.1.rc7). >> >> qemu-system-aarch64 -enable-kvm -object rme-guest,id=rme0, \ >> -machine virt,gic-version=3,confidential-guest-support=rme0 \ >> -cpu host,pmu=off \ >> -smp maxcpus=2,cpus=2,sockets=1,clusters=1,cores=1,threads=2 \ >> -m 2G -object memory-backend-ram,id=mem0,size=2G \ >> -numa node,nodeid=0,cpus=0-1,memdev=mem0 \ >> -serial mon:stdio -monitor none -nographic -nodefaults \ >> -kernel /mnt/linux/arch/arm64/boot/Image \ >> -initrd /mnt/buildroot/output/images/rootfs.cpio.xz \ >> -append earlycon=pl011,mmio,0x10009000000 \ >> -device pcie-root-port,bus=pcie.0,chassis=1,id=pcie.1 \ >> -device pcie-root-port,bus=pcie.0,chassis=2,id=pcie.2 \ >> -device pcie-root-port,bus=pcie.0,chassis=3,id=pcie.3 \ >> -device pcie-root-port,bus=pcie.0,chassis=4,id=pcie.4 \ >> -netdev tap,id=tap1,vhost=on,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown \ >> -device virtio-net-pci,bus=pcie.2,netdev=tap1,mac=b8:3f:d2:1d:3e:c0 > > Tested with private RAM backend, THP left enabled (and additional KVM and > RMM patches that will be included in v15) looks like the net interface > comes up cleanly. > > Probably it is best to sync up on the upcoming v15 posting that I am > testing in the background to make sure you don't spend more time chasing > it. > Thanks for your confirmation. For every respin of the arm/cca host series, I try to give it a test to make sure nothing gets broken in my coverage. For this specific revision (v14), more time was actually spent to rebase Jean's qemu (branch: cca/latest) to upstream so that I can do the tests. Lets wait for a while to see what we will have in v15 and the qemu series you're going to post, and I will give it another try. One unrelated question is 64KB granule size, it's not supported by upstream TF-RMM "main" or "topics/rmm-v2.0-poc_2" branch, not sure about the plan when this will be supported in TF-RMM. Since 64KB isn't supported by TF-RMM, I was unable to test 64KB page size. Upstream EDK2 doesn't support realm guest yet even some of related commits have been merged. So I still use linaro's one at "https://git.codelinaro.org /linaro/dcap/edk2 (branch: cca/latest). Thanks, Gavin > Thanks, > Lorenzo > >> >> The virtio-net-pci starts to work with the shareable memory-backend. >> >> -object memory-backend-ram,id=mem0,size=2G,share=yes >> >> Note that THP is disabled on my host. >> >> root@host:~# cat /sys/kernel/mm/transparent_hugepage/enabled >> always madvise [never] >