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Subject: Re: [virtio-comment] RE: [virtio-dev] Re: [virtio-comment] [PATCH] Add virtio rpmb device specification
On Mon, Aug 05, 2019 at 02:39:00AM +0000, Huang, Yang wrote: > > > > > > > > > On 29/07/19 09:48, Huang Yang wrote: > > > > > > > > > > > > > > > > > > But virtualization software like Qemu doesn't provide > > > > > > > > > eMMC/UFS/NVMe RPMB emulation. It blocks the OS like Trusty > > > > > > > > > or OP-TEE running in a virtualization environment. For > > > > > > > > > instance, Google right now uses another way to work around > > > > > > > > > RPMB emulation issue when running Trusty in > > > > > > > > ARM Qemu: > > > > > > > > > https://android.googlesource.com/trusty/external/trusty/+/ > > > > > > > > > refs > > > > > > > > > /hea > > > > > > > > > ds/m > > > > > > > > > aster/test-runner/ > > > > > > > > > > > > > > > > > > Virtio RPMB standardization will definitely benefit > > > > > > > > > OP-TEE, Google Trusty TEE, Qemu, OVMF or other modules to > > > > > > > > > develop the RPMB based secure storage in virtualization. > > > > > > > > > > > > > > > > > > > > > > > > > Is there any reason to use a new virtio-blk device, and not > > > > > > > > add this functionality to virtio-blk? > > > > > > > > > > > > > > > > Paolo > > > > > > > > > > > > > > RPMB does not behave as a blk device. It doesn't have block device > > APIs. > > > > > > > Current virtio blk features or definitions in spec are mostly > > > > > > > useless or > > > > > > inapplicable to virtio rpmb. > > > > > > > It performs a different behaviors from the operations on a blk device. > > > > > > > Key, writer counter or nonce are required to read/write on it. > > > > > > > If add it to blk device, it will not only cause to a higher > > > > > > > complexity, but also > > > > > > cause to two different behaviors on a same device. > > > > > > > > > > > > > > > > > > > > > > > > > Well it seems that current RPMB implementations are all tied to > > > > > > a storage device, like MMC or NVMe. Why is that and why doesn't > > > > > > the same > > > > logic apply here? > > > > > > > > > > > > -- > > > > > > MST > > > > > > > > > > > > > > > > RPMB is a mandatory hardware partition of eMMC, UFS and optional > > > > > for > > > > NVMe. > > > > > It is standardized by JEDEC and NVMe. > > > > > This partition is different from the user data partition that blk device > > emulates. > > > > > It provides a signed access in an authenticated and replay > > > > > protected manner that blk device does not perform. Only RPMB key > > > > > owner can write to it while anybody can access to a user data partition. > > > > > > > > Sorry if I'm being dense, so how is this different from e.g. NVMe? > > > > > > > > -- > > > > MST > > > > > > Do you refer to the difference between NVMe RPMB and eMMC RPMB? > > > Or between NVMe RPMB partition and NVMe user data partition? > > > > I refer to the fact that NVMe and eMMC are storage devices that support an > > RPMB partition. Why is virtio blk different? > > wouldn't it make sense for it to support an RPMB partition? > > RPMB is not a blk device for the reasons: > 1. It does not have blk device APIs, or is not applicable. That's a circular argument, isn't it? > 2. Moreover, it performs different behaviors. > It behaves in an authenticated and anti-replay manner, e.g. RPMB access is signed by the RPMB key, and requires a write counter. > 3. For RPMB and common disks, they are hardware soldered but functions independent. > > What do you think? The question to ask is whether guests use RPMB to protect contents of a storage device from tampering. If yes then it makes sense as part of the storage device it protects. for example mmc creates a bunch of fake block devices for it - it seems likely userspace is used to dealing with it this way. Another question to answer is whether by adding a kernel driver within guest you actually make guest userspace to work. -- MST
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