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[175.34.8.244]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2c7f63b27f4sm34866665ad.53.2026.06.26.00.43.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 26 Jun 2026 00:43:47 -0700 (PDT) Message-ID: <8da87878-2a5d-478a-a280-60dbed7ad1b9@redhat.com> Date: Fri, 26 Jun 2026 17:43:34 +1000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v14 29/44] arm64: RMI: Runtime faulting of memory To: Suzuki K Poulose , Lorenzo Pieralisi Cc: 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: <20260513131757.116630-1-steven.price@arm.com> <20260513131757.116630-30-steven.price@arm.com> <3359f788-07fa-41a1-9ac7-45c58577c1fa@redhat.com> <1e39094f-7fa3-4ef1-be54-53d7a8643506@redhat.com> <98d2a0f3-b831-466a-8212-5bcf97ad9d8b@arm.com> Content-Language: en-US From: Gavin Shan In-Reply-To: <98d2a0f3-b831-466a-8212-5bcf97ad9d8b@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 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. There are more findings after more experiments: this virtio-net-pci device has 3 queues or vrings (Rx/Tx/Ctrl). The Rx/Tx/Ctrl queue are populated in order one after one. In the guest kernel, I intentionally write fixed data (0x0123456789abcdef) to the first 8 bytes of the queue when it gets populated, and stop the guest at random points to see if the data is gone. I found that the data written to Rx/Tx queue are lost after Ctrl queue is allocated. The data written to Rx/Tx queue is lost if the guest stops (B). The data written to Rx/Tx queue isn't lost if the guest stops at (A). I can see the pattern (0x0123...cdef) by dumping the physcial memory through 'pmemsave' command in qemu. DMA allocation ============== dma_alloc_coherent dma_alloc_attrs dma_direct_alloc __dma_direct_alloc_pages dma_set_decrypted // (A) No data lost if being stopped here for the Ctrl queue memset(ret, 0, size) // (B) Data lost after being stopped after memset() for the Ctrl queue The memset() on the Ctrl queue should trigger a stage2 page fault. It seems the page fault enforces the shared pages for Rx/Tx queue to be dropped? I need to add more debugging code and track it down. > Suzuki > > >> >> - On QEMU, the updated vring (struct vring_desc) at GPA 0x46880000 isn't seen. All the >>    data in that adress are zeros. >> >>    ====> virtqueue_split_pop: vdev=, sz=0x38, queue_index=0x0, vq->vring.num=0x100 >>    virtqueue_split_pop: last_avail_idx=0x0, head=0x0 >>    address_space_read_cached_slow: cache@0xffff1c036440, addr=0x0, buf=0xffffeee34880, len=0x10 >>    address_space_read_cached_slow: cache: ptr=0x0, xlat=0x10046880000, len=0x1000, mrs=, is_write=no >>    address_space_read_cached_slow: translated to mr=, mr_addr=0x6880000, l=0x10 >>    flatview_read_continue_step: mr=, host=0xffff23e00000, mr_addr=0x6880000, ram_ptr=0xffff2a680000 >>    virtqueue_split_pop: desc: 0000000000000000 - 00000000 - 00000000 - 00000000 >>    qemu-system-aarch64: virtio: zero sized buffers are not allowed >> >> Thanks, Gavin