Re: [PATCH v1] virtio-blk: Add inline encryption support
Linlin Zhang <[email protected]> Tue, 3 Feb 2026 18:06:33 +0800
| Newsgroups | dev.linux.lists.virtio-dev |
|---|---|
| Message-ID | <[email protected]> |
On 2/2/2026 11:56 PM, Stefan Hajnoczi wrote: > On Fri, Jan 30, 2026 at 06:23:55PM +0800, Linlin Zhang wrote: >> Thank you for the review. I’ve added some clarifications and potential updates. >> Could you please take another look before I send a new patch? >> >> On 1/28/2026 5:09 AM, Stefan Hajnoczi wrote: >>> On Tue, Jan 27, 2026 at 10:20:32PM +0800, Linlin Zhang wrote: >>>> From: linlzhan <[email protected]> >>>> >>>> Inline encryption on virtio block can only be supported when >>>> the new feature bit VIRTIO_BLK_F_ICE is negotiated. >>>> >>>> Extend struct virtio_blk_config and struct virtio_blk_req, >>>> so that crypto capabilities can be got in the frontend and >>>> encryption metadata can be sent to the backend, together with >>>> each I/O transaction. >>> >>> This looks like a Self-Encrypting Drives feature along the lines of TCG >>> Opal: >>> https://en.wikipedia.org/wiki/Opal_Storage_Specification >>> >>> Would it make sense to implement TCG Opal instead of defining a new >>> interface? That would make this more familiar to users and simplify >>> integration into existing tools like sedutil and cryptsetup (e.g. by >>> supporting the <linux/sed-opal.h> ioctl interface). >> >> This patch is for the FBE (File Based Encryption) support on UFS/EMMC >> storage with ICE (Inline Crypto Engine) enabled. TCG Opal is only applicable >> to SED (self-encrypting drives), not applicable to ICE (Inline Crypto Engine). >> >> In Automotive or Embedded scenario, UFS/EMMC generally is used. The disk >> encryption on them is supported by the ICE pipeline of SOC, rather SSD >> controller, so we couldn't use TCG Opal here. > > Okay. Is there a specification that this interface needs to comply with? > > If not, you can include a link to the Linux inline encryption > documentation in the commit description: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/block/inline-encryption.rst > > Having a reference will will help the discussion. That way we can be > confident the VIRTIO spec changes will be widely useful beyond a single > use case and easy to implement in drivers because they follow an > existing interface. ACK > >> >>> >>>> Fixes: https://github.com/oasis-tcs/virtio-spec/issues/238 >>>> >>>> Change-Id: Ic23b2137e5d9a599d826e06c279f1b614d79abdf >>>> Signed-off-by: linlzhan <[email protected]> >>>> --- >>>> device-types/blk/description.tex | 69 ++++++++++++++++++++++++++++++++ >>>> 1 file changed, 69 insertions(+) >>>> >>>> diff --git a/device-types/blk/description.tex b/device-types/blk/description.tex >>>> index 2712ada..23d8dc0 100644 >>>> --- a/device-types/blk/description.tex >>>> +++ b/device-types/blk/description.tex >>>> @@ -66,6 +66,11 @@ \subsection{Feature bits}\label{sec:Device Types / Block Device / Feature bits} >>>> (ZNS). For brevity, these standard documents are referred as "ZBD standards" >>>> from this point on in the text. >>>> >>>> +\item[VIRTIO_BLK_F_ICE(22)] Inline Crypto Extensions are supported. When this >>>> + is negotiated, the device exposes crypto characteristics in configuration >>>> + space and the driver SHALL provide an extended request header containing a >>> >>> SHALL, MUST, MAY, etc are only used in the normative sections of the >>> spec. >>> >>> Why "SHALL"? Does this mean the device must be prepared to receive >>> requests without the payload field when VIRTIO_BLK_F_ICE is negotiated? >>> How should the device behave in that case: fail the request or perform >>> I/O without crypto? >> >> This section - 5.2.3 Feature bits - is a normative section. > > \section{Block Device}\label{sec:Device Types / Block Device} > ... > \subsection{Feature bits}\label{sec:Device Types / Block Device / Feature bits} > > No, this is a non-normative section. The normative sections are the > "Device Requirements" (\devicenormative) and "Driver Requirements" > (\drivernormative) sections. OK, as this is a non-normative section, can I use lowercase 'shall', 'must'.etc here? > >> >> What's expected for VIRTIO_BLK_F_ICE feature bit is that configuration space >> must be prepared with the exposed crypto characteristics and the virtio block >> frontend must sent a virtblk request with encryption metadata packed into >> when VIRTIO_BLK_F_ICE is negotiated and hardware crypto is supported. >> >> By replacing 'SHALL' with 'MUST' here, Is the following rewording fine? >> >> Inline Crypto Extensions are supported. When this is negotiated, the device MUST >> expose crypto characteristics in configuration space and the driver MUST provide >> an extended request header containing a crypto payload for block I/O if the >> hardware supports inline crypto. If this feature bit is negotiated, but hardware >> inline crypto doesn't support, the device SHOULD perform I/O without crypto. >> >> I'll add hw_enabled (type: u8) to virtio_blk_crypto_characteristics to indicate >> whether the host supports hardware inline encryption. > > I still have a question about this: why would a device advertise > VIRTIO_BLK_F_ICE but report hw_enabled = 0? I'm not sure how this is > functionally different from a device that does not report > VIRTIO_BLK_F_ICE. It seems simpler for devices to only advertise > VIRTIO_BLK_F_ICE when they support inline encryption. ACK. Previously I assume VIRTIO_BLK_F_ICE is negotiated even ICE (Inline Crypto Engine) isn't enabled. Seems it isn't needed. a device should only advertise VIRTIO_BLK_F_ICE when ICE is enabled. Correct the statement as the following. Inline Crypto Extensions are supported. Only when this feature b is negotiated, the device need expose crypto characteristics in configuration space and the driver need provide an extended request header containing a crypto payload for block I/O. > >>> >>>> + crypto payload for block I/O. >>>> + >>>> \end{description} >>>> >>>> \subsubsection{Legacy Interface: Feature bits}\label{sec:Device Types / Block Device / Feature bits / Legacy Interface: Feature bits} >>>> @@ -128,6 +133,11 @@ \subsection{Device configuration layout}\label{sec:Device Types / Block Device / >>>> u8 model; >>>> u8 unused2[3]; >>>> } zoned; >>>> + struct virtio_blk_crypto_characteristics { >>>> + __virtio16 slot_info; >>>> + __virtio16 reserved; >>>> + __virtio32 capability; >>>> + } crypto; >>>> }; >>>> \end{lstlisting} >>>> >>>> @@ -215,6 +225,25 @@ \subsection{Device configuration layout}\label{sec:Device Types / Block Device / >>>> terminated by the device with a "zone resources exceeded" error as defined for >>>> specific commands later. >>>> >>>> +If the VIRTIO_BLK_F_ICE feature is negotiated, then in >>>> +\field{virtio_blk_crypto_characteristics}, >>>> +\begin{itemize} >>>> +\item \field{slot_info} value packs two 8-bits values: >>>> + \begin{itemize} >>>> + \item Bits~\[15:8] (\emph{max\_slots}): the maximum number of supported >>>> + crypto key slots. >>>> + \item Bits~\[7:0] (\emph{slot\_offset}): an offset applied to slot numbering. >>>> + \end{itemize} >>>> +\item \field{capability} value packs four 8-bits values: >>>> + \begin{itemize} >>>> + \item Bits~\[31:24]: crypto algorithm id. >>>> + \item Bits~\[23:16]: mask of data unit size. >>>> + \item Bits~\[15:8]: crypto key size. >>>> + \item Bits~\[7:0]: unused. >>>> + \end{itemize} >>> >>> Why are these fields packed? Configuration Space can have u8 fields. >> >> Given that §. 4.2.2.2 saying "For the device-specific configuration space, >> the driver MUST use 8 bit wide accesses for 8 bit wide fields, 16 bit wide >> and aligned accesses for 16 bit wide fields and 32 bit wide and aligned >> accesses for 32 and 64 bit wide fields.", these fields are packed for a >> efficient read from the configuration space. > > I see. I suggest mentioning this explicitly: "value packs two 8-bits > values to reduce the number of Configuration Space reads". ACK > >>> >>> These fields are not sufficiently documented. Where are the crypto >>> algorithm ids listed, etc? >> >> Can I reword it as the following? > > Yes, looks good in general. I have some comments below. > >> >> \item Bits~\[31:24]: crypto algorithm identifiers. >> The device SHALL support reporting and negotiating cryptographic >> algorithms using the following algorithm identifiers: >> \begin{lstlisting} >> CRYPTO_ALG_AES_XTS = 0x0 >> CRYPTO_ALG_BITLOCKER_AES_CBC = 0x1 >> CRYPTO_ALG_AES_ECB = 0x2 >> CRYPTO_ALG_ESSIV_AES_CBC = 0x3 >> \end{lstlisting} >> These identifiers abstract the underlying hardware crypto implementation >> and MUST NOT assume any operating‑system‑specific data structures or >> constants. > > (The MUST NOT part needs to be in a \devicenormative or \drivernormative > sections, but I think "MUST NOT" can be replaced with "does not" here > because it actually describes the design of the interface rather than > imposing requirements on device implementors.) ACK > >> \item Bits~\[23:16]: mask of data unit size. When bit j in this field >> (j=0......7)is set, a data unit size of 512*2^j bytes is slected. > > s/)is set/) is set/ > s/slected/selected/ ACK > > How is the data unit size used? Does it affect the allowed request sizes > of the device? > > For example, if the mask is 0x2, so that mean request sizes must be > multiples of 1 KiB? The data unit size is only used in the control flow of programing a key into ICE slot. It hasn't impact on the virtblk request size. For instance, if the mask is 0x2, so that mean the encryption granularity is (2^1 * 512 = ) 1024 bytes. I.e. ICE hardware increase DUN (Date Unit Number) per 1024 bytes to do encryption/decryption. > > By the way, I'm not sure whether "j=0......7" mean that a mask value of > 0x2 has j=1 or j=6? Usually bits are numbered right-to-left from least > significant bit to most significant bit. A mask value of 0x2 has j=1. It comply with right-to-left number sequence. > >> \item Bits~\[15:8]: crypto key size identifiers. >> \begin{lstlisting} >> CRYPTO_KEY_SIZE_INVALID = 0x0 >> CRYPTO_KEY_SIZE_128_BITS = 0x1 >> CRYPTO_KEY_SIZE_192_BITS = 0x2 >> CRYPTO_KEY_SIZE_256_BITS = 0x3 >> CRYPTO_KEY_SIZE_512_BITS = 0x4 >> \end{lstlisting} >> >>> >>> How can a device support multiple algorithms? I think Configuration >>> Space may not be flexible enough for this. You could introduce a >>> GET_CRYPTO_INFO request type that allows the driver to fetch arrays of >>> crypto algorithm characteristics. >> >> Virtio block driver need register crypto capability for request_queue of >> virtio block device. That means virtio block frontend need get crypto >> capability before virtio block device is ready. But the request can only >> be sent after the virtio block device is ready. Thus I think it's impossible >> to get such capabilities from the backend via a new request type, event >> though the hardware in the host may support a few algorithms (the actual >> number of algorithms will change depending on the vendor manufacturer.). >> Thus I assume the host only configure and expose one hardware crypto >> capability to the virtual machine and virtio block frontend gets is >> through configuration space. > > The zoned storage feature also needs to use the virtqueues during driver > initialization in order to report zones. Here is the Linux virtio_blk.c > driver code: > > static int virtblk_probe(struct virtio_device *vdev) > { > ... > virtio_device_ready(vdev); > > /* > * All steps that follow use the VQs therefore they need to be > * placed after the virtio_device_ready() call above. > */ > if (IS_ENABLED(CONFIG_BLK_DEV_ZONED) && > (lim.features & BLK_FEAT_ZONED)) { > err = blk_revalidate_disk_zones(vblk->disk); > if (err) > goto out_cleanup_disk; > } > > err = device_add_disk(&vdev->dev, vblk->disk, virtblk_attr_groups); > > Is it possible to call blk_crypto_register() between > virtio_device_read() and device_add_disk()? Thanks! Referring to zoned storage feature, if we use the virtqueues to get crypto capabilities, we need extend in_hdr in struct virtblk_req to add new fields for crypto capability. Like the following field crypto_append. Is it fine? we can not use a fixed-size array for crypto capabilities. Because the number of the capabilities differs for different OEMs and storage devices. struct virtblk_req { /* Out header */ struct virtio_blk_outhdr out_hdr; /* In header */ union { u8 status; /* * The zone append command has an extended in header. * The status field in zone_append_in_hdr must always * be the last byte. */ struct { __virtio64 sector; u8 status; } zone_append; struct { u8 num; __virtio32 *capabilities; } crypto_append; } in_hdr; size_t in_hdr_len; struct sg_table sg_table; struct scatterlist sg[]; }; > >> >>> >>>> +\end{itemize} >>>> + >>>> + >>>> \subsubsection{Legacy Interface: Device configuration layout}\label{sec:Device Types / Block Device / Device configuration layout / Legacy Interface: Device configuration layout} >>>> When using the legacy interface, transitional devices and drivers >>>> MUST format the fields in struct virtio_blk_config >>>> @@ -278,6 +307,10 @@ \subsection{Device Initialization}\label{sec:Device Types / Block Device / Devic >>>> \field{zoned} can be read by the driver to determine the zone >>>> characteristics of the device. All \field{zoned} fields are read-only. >>>> >>>> +\item If the VIRTIO_BLK_F_ICE feature is negotiated, the fields in >>>> + \field{crypto} can be read by the driver to determine the inline crypto >>>> + characteristics of the device. All \field{crypto} fields are read-only. >>>> + >>>> \end{enumerate} >>>> >>>> \drivernormative{\subsubsection}{Device Initialization}{Device Types / Block Device / Device Initialization} >>>> @@ -317,6 +350,9 @@ \subsection{Device Initialization}\label{sec:Device Types / Block Device / Devic >>>> driver SHOULD ignore all other fields in \field{zoned}. >>>> \end{itemize} >>>> >>>> +If the VIRTIO_BLK_F_ICE feature is negotiated, then the driver must validate >>>> + the max_slots in \field{slot_info} before the slot usage. >>>> + >>>> \devicenormative{\subsubsection}{Device Initialization}{Device Types / Block Device / Device Initialization} >>>> >>>> Devices SHOULD always offer VIRTIO_BLK_F_FLUSH, and MUST offer it >>>> @@ -402,6 +438,16 @@ \subsection{Device Initialization}\label{sec:Device Types / Block Device / Devic >>>> \item the device MUST initialize padding bytes \field{unused2} to 0. >>>> \end{itemize} >>>> >>>> +If the VIRTIO_BLK_F_ICE feature is negotiated, then the fields in \field{cryto} >>> >>> s/cryto/crypto/ >> >> Thanks for the correction. Update it in new patch. >> >>> >>>> +struct in the configuration space MUST be set by the device. >>>> +\begin{itemize} >>>> +\item the \field{slot_info} field of \field{crypto} MUST be set by the device to a >>>> + max_slots in the higher 8 bits and slot_offset in the lower 8 bits. >>>> + >>>> +\item the \field{capability} field of \field{crypto} MUST be set by the device >>>> + to a crypto capability read from the storage register. >>>> +\end{itemize} >>>> + >>>> \subsubsection{Legacy Interface: Device Initialization}\label{sec:Device Types / Block Device / Device Initialization / Legacy Interface: Device Initialization} >>>> >>>> Because legacy devices do not have FEATURES_OK, transitional devices >>>> @@ -436,6 +482,13 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope >>>> le32 type; >>>> le32 reserved; >>>> le64 sector; >>>> + struct virtio_blk_crypto_payload { >>>> + u8 slot; >>>> + u8 activate; >>>> + le16 reserved1; >>>> + le32 reserved2; >>>> + le64 data_unit_num; >>>> + } payload; >>>> u8 data[]; >>>> u8 status; >>>> }; >>>> @@ -463,6 +516,20 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope >>>> the read or write is to occur. This field is unused and set to 0 for >>>> commands other than read, write and some zone operations. >>>> >>>> +The \field{payload} consists of the encryption information for current >>>> +request. It need to be set by the driver only when the feature VIRTIO_BLK_F_ICE >>>> +is negotiated. >>> >>> "set" is ambiguous: does it meaning filling in the fields or does it >>> mean the fields are only present when VIRTIO_BLK_F_ICE is negotiated >>> (this distinction is important if other features add more fields after >>> payload in the future). >>> >>> The sentence could be reworded: >>> >>> It is only present when the VIRTIO_BLK_F_ICE feature is negotiated and >>> \field{type} is VIRTIO_BLK_T_IN or VIRTIO_BLK_T_OUT. >>> >>> (I'm not sure whether DISCARD, WRITE_ZEROES, or SECURE_ERASE also need >>> the payload field. It seems like GET_ID and GET_LIFETIME do not need the >>> payload field.) >> >> Accept and update it as the following. >> >> It is only present when the VIRTIO_BLK_F_ICE feature is negotiated and >> +\field{type} is VIRTIO_BLK_T_IN, VIRTIO_BLK_T_OUT or VIRTIO_BLK_T_FLUSH. > > Thanks. > >> >>> >>>> +\begin{itemize} >>>> +\item The \field{slot} filed in \field{payload} indicates the ICE >>> >>> s/filed/field/ >> >> Thanks for the correction. Update it in new patch. >> >>> >>>> + (Inline Crypto Encryption) slot index where the key resides in. >>> >>> s/where the key resides in/where the key resides/ >> >> Thanks for the correction. Update it in new patch. >> >>> >>>> + >>>> +\item The \field{activate} filed in \field{payload} implies this is a >>> >>> s/filed/field/ >> >> Thanks for the correction. Update it in new patch. >> >>> >>>> + encryption request. >>> >>> Does "encryption" really mean just encryption or does it mean >>> encryption for writes and decryption for reads? >> >> Actually encryption request here means both encryption for writes and >> decryption for reads. Need I modify it as the following? > > If writing "encryption/decryption" is too tedious, maybe use the feature > name ("inline encryption"). That way it's clear we're talking about the > feature and not specifically about an encryption operation (vs a > decryption operation). ACK > >> >> \item The \field{activate} field in \field{payload} implies this is a >> encryption write request or decryption read request. >> >>> >>>> + >>>> +\item The \field{data_unit_num} filed in \field{payload} indicates the >>> >>> s/filed/field/ >> >> Thanks for the correction. Update it in new patch. >> >>> >>>> + starting block of the request. >>>> +\end{itemize} >>>> + >>>> VIRTIO_BLK_T_IN requests populate \field{data} with the contents of sectors >>>> read from the block device (in multiples of 512 bytes). VIRTIO_BLK_T_OUT >>>> requests write the contents of \field{data} to the block device (in multiples >>>> @@ -912,6 +979,8 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope >>>> successfully, failed, or were processed by the device at all if the request >>>> failed with VIRTIO_BLK_S_IOERR. >>>> >>>> +A driver MUST set \field{activate} to 0 for a non VIRTIO_BLK_F_ICE request. >>> >>> Please explicitly list request types where the payload field is present >>> and where activate is optional. >> >> How about adding the following supplement? >> >> \begin{itemize} >> \item only when the block request contains crypto context and the request type > > I'm not sure what "when the block request contains crypto context" > means. Is that the same as "when VIRTIO_BLK_F_ICE has been negotiated"? No, crypto context means bio_crypt_ctx in BIO struct. struct bio { ... #ifdef CONFIG_BLK_INLINE_ENCRYPTION struct bio_crypt_ctx *bi_crypt_context; #endif ... } When VIRTIO_BLK_F_ICE has been negotiated, virtio block backend receives crypto payload from virtio block frontend, and the crypto payload, together with I/O transaction, is sent to block layer of the host finally. The crypto payload is used to construct the bio_crypt_ctx filed of BIO. > >> is one of VIRTIO_BLK_T_IN, VIRTIO_BLK_T_OUT and VIRTIO_BLK_T_FLUSH, >> \field{activate} MUST be set to 1. >> >> \item \field{activate} should be set to 0 for all the other cases. >> \end{itemize} >> >>> >>>> + >>>> The following requirements only apply if the VIRTIO_BLK_F_ZONED feature is >>>> negotiated. >>>> >>>> -- >>>> 2.34.1 >>>> >>>> >>