From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id AC7132EB859; Fri, 26 Jun 2026 08:53:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782463995; cv=none; b=t6oLeug9aisy6j0DLhSNWFoQ4LwTpBgyAkbak3AlSIiHPZppzDv4sBKFHMY4Sz46u+zPjR4ZHoSfl11wqAU3bq6niTUl5Ed0Y468idmV2e5NaPlGIyKQuVcMWQ1ZfSV46VYH9TM5vaE5C2vTw2HlQuWHu2gm6TM5BSyc/m71HEo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782463995; c=relaxed/simple; bh=p9vOkbqaBZi9cvX5i54t8dgEDQi2LWFk1zzsZEJpODY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pHnvLJZm4EfC3rjg0BRrYgkDy+B4pNx+8ozM+0V8ydrhBkT50Yl9t09VJrPOg4FIuWLYHDxrxWRFLBx3zjWYLa5B+cQIMZdPFds7qUz2q9LEyfXnhi8t8mZcdlvMDEXUqfarXBRZLqJHzIufc1BsEynnU2+pGDOu8Qwrl4PsrK4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=JQR2Jx0O; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="JQR2Jx0O" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7F1752247; Fri, 26 Jun 2026 01:47:13 -0700 (PDT) Received: from [10.57.28.79] (unknown [10.57.28.79]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D819B3F905; Fri, 26 Jun 2026 01:47:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1782463638; bh=p9vOkbqaBZi9cvX5i54t8dgEDQi2LWFk1zzsZEJpODY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=JQR2Jx0OWyoQ0O6coNwSG0GeGJhuSAJTr/ID0QDqM9rD++MHxvkPahYtcDC8vrT1I CArES9Vov5l7eK0s/nZuq8ROmyxo6kDWjlW1se5CL/5VQKBPapEeN0uyQrUcZj6FIZ gwXB8AZmlEq2CJhAq6Xy5+g4TdrbgoOcm5UrJ5yQ= Message-ID: <9482dfbc-4d96-47ba-a615-f4ba0bda833f@arm.com> Date: Fri, 26 Jun 2026 09:47:13 +0100 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev 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 Content-Language: en-GB To: Gavin Shan , 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> <8da87878-2a5d-478a-a280-60dbed7ad1b9@redhat.com> From: Suzuki K Poulose In-Reply-To: <8da87878-2a5d-478a-a280-60dbed7ad1b9@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 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. Suzuki > > 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 >