* RE: [PATCH] scsi: ufs: docs: Describe how to test with QEMU
2026-10-11 10:33 ` [PATCH] scsi: ufs: docs: Describe how to test with QEMU Stanley Jhu
@ 2026-10-12 5:04 ` Alim Akhtar
2026-10-12 11:09 ` Bean Huo
1 sibling, 0 replies; 3+ messages in thread
From: Alim Akhtar @ 2026-10-12 5:04 UTC (permalink / raw)
To: 'Stanley Jhu', 'Martin K. Petersen',
'James E.J. Bottomley', 'Jonathan Corbet'
Cc: 'Bart Van Assche', 'Shuah Khan',
'Randy Dunlap', 'Jeuk Kim', 'Bean Huo',
linux-scsi, linux-doc, linux-kernel
> -----Original Message-----
> From: Stanley Jhu <stanleyjhu@google.com>
> Sent: Sunday, October 11, 2026 4:03 PM
> To: Martin K. Petersen <mkp@kernel.org>; James E.J. Bottomley
> <James.Bottomley@HansenPartnership.com>; Jonathan Corbet
> <corbet@lwn.net>
> Cc: Bart Van Assche <bvanassche@acm.org>; Alim Akhtar
> <alim.akhtar@samsung.com>; Shuah Khan <skhan@linuxfoundation.org>;
> Randy Dunlap <rdunlap@infradead.org>; Jeuk Kim
> <jeuk20.kim@samsung.com>; Bean Huo <beanhuo@iokpp.de>; linux-
> scsi@vger.kernel.org; linux-doc@vger.kernel.org; linux-
> kernel@vger.kernel.org
> Subject: [PATCH] scsi: ufs: docs: Describe how to test with QEMU
>
> QEMU emulates a UFS host controller and logical units, but the kernel tree
> does not mention it, so developers without UFS hardware have no
> documented way to exercise the UFS core.
>
> Add a short section with the required kernel options, an example QEMU
> command line, and what the emulation does not cover.
>
> Signed-off-by: Stanley Jhu <stanleyjhu@google.com>
> ---
Thanks Stanley!
This helps
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] scsi: ufs: docs: Describe how to test with QEMU
2026-10-11 10:33 ` [PATCH] scsi: ufs: docs: Describe how to test with QEMU Stanley Jhu
2026-10-12 5:04 ` Alim Akhtar
@ 2026-10-12 11:09 ` Bean Huo
1 sibling, 0 replies; 3+ messages in thread
From: Bean Huo @ 2026-10-12 11:09 UTC (permalink / raw)
To: Stanley Jhu, Martin K. Petersen, James E.J. Bottomley, Jonathan Corbet
Cc: Bart Van Assche, Alim Akhtar, Shuah Khan, Randy Dunlap, Jeuk Kim,
linux-scsi, linux-doc, linux-kernel
Stanley,
Thanks, this is very useful, a few comments as below:
On Sun, 2026-10-11 at 18:33 +0800, Stanley Jhu wrote:
> QEMU emulates a UFS host controller and logical units, but the kernel
> tree does not mention it, so developers without UFS hardware have no
> documented way to exercise the UFS core.
>
> Add a short section with the required kernel options, an example QEMU
> command line, and what the emulation does not cover.
>
> Signed-off-by: Stanley Jhu <stanleyjhu@google.com>
> ---
> Documentation/scsi/ufs.rst | 33 +++++++++++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
> diff --git a/Documentation/scsi/ufs.rst b/Documentation/scsi/ufs.rst
> index a7b2b2ed1c3a..1ff1c8218bf1 100644
> --- a/Documentation/scsi/ufs.rst
> +++ b/Documentation/scsi/ufs.rst
> @@ -19,6 +19,7 @@ Universal Flash Storage
> 3.4 SCSI Error handling
> 4. BSG Support
> 5. UFS Reference Clock Frequency configuration
> + 6. Testing with QEMU
>
>
> 1. Overview
> @@ -208,3 +209,35 @@ the UFS specification. UFS subsystem will attempt to read
> the value when
> executing common controller initialization. If the value is available, UFS
> subsystem will ensure the bRefClkFreq attribute of the UFS storage device is
> set accordingly and will modify it if there is a mismatch.
> +
> +6. Testing with QEMU
> +====================
> +
> +QEMU emulates a UFS host controller as a PCI device named "ufs" and
> +logical units named "ufs-lu". This can be used to test changes to the
> +UFS core and to ufshcd-pci without UFS hardware.
> +
should here state the minimum QEMU version for the ufs device, and for mcq=on,
since the older version QEMU may not have them or one of them.
> +Enable the following kernel options on top of the architecture
> +defconfig::
> +
> + CONFIG_SCSI_UFSHCD=y
> + CONFIG_SCSI_UFSHCD_PCI=y
> + CONFIG_BLK_DEV_SD=y
> +
> +Example for an arm64 guest with one 1 GiB logical unit::
> +
> + qemu-img create -f raw ufs.img 1G
> + qemu-system-aarch64 -M virt -cpu max -smp 4 -m 2G -nographic \
> + -kernel arch/arm64/boot/Image -initrd rootfs.cpio.gz \
> + -append "console=ttyAMA0" \
> + -drive file=ufs.img,if=none,id=lu0,format=raw \
> + -device ufs,id=ufs0,serial=0001,mcq=on \
> + -device ufs-lu,drive=lu0,bus=ufs0,lun=0
> +
> +The logical unit appears as a SCSI disk (/dev/sda).
maybe here adds "for example"-> The logical unit appears as a SCSI disk (for
example /dev/sda)
> Drop "mcq=on" to
> +test the single doorbell mode instead of MCQ. The same -device options
> +work with qemu-system-x86_64.
> +
> +The emulation does not model UniPro, M-PHY, power mode changes,
I am cconfused by this statement, since I checked QEMU, the latest QEMU accepts
some UIC commands such as hibern8 enter/exit, if I am correct, here "accepts but
does not model" would be more precise, you can check hw/ufs/ufs.c:
static void ufs_process_uiccmd(UfsHc *u, uint32_t val)
> +hibernation or clock gating hardware, and vendor host drivers are not
> +exercised. Changes in those areas still need testing on real hardware.
Kind regards,
Bean
^ permalink raw reply [flat|nested] 3+ messages in thread