From: Elliot Berman <quic_eberman@quicinc.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>,
Bjorn Andersson <quic_bjorande@quicinc.com>,
Murali Nalajala <quic_mnalajal@quicinc.com>,
Trilok Soni <quic_tsoni@quicinc.com>,
Srivatsa Vaddagiri <quic_svaddagi@quicinc.com>,
Carl van Schaik <quic_cvanscha@quicinc.com>,
Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>,
Andy Gross <agross@kernel.org>,
Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
"Jassi Brar" <jassisinghbrar@gmail.com>,
<linux-arm-kernel@lists.infradead.org>,
"Mark Rutland" <mark.rutland@arm.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Sudeep Holla <sudeep.holla@arm.com>,
"Marc Zyngier" <maz@kernel.org>, Rob Herring <robh+dt@kernel.org>,
"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
Jonathan Corbet <corbet@lwn.net>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Arnd Bergmann <arnd@arndb.de>, <devicetree@vger.kernel.org>,
<linux-doc@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 14/14] tty: gunyah: Add tty console driver for RM Console Services
Date: Mon, 10 Oct 2022 13:58:00 -0700 [thread overview]
Message-ID: <ca42d89e-9e19-0536-0951-2c123d898892@quicinc.com> (raw)
In-Reply-To: <Y0R/QbysXa6ebNd8@kroah.com>
On 10/10/2022 1:23 PM, Greg Kroah-Hartman wrote:
> On Sun, Oct 09, 2022 at 01:59:21PM -0700, Elliot Berman wrote:
>>
>>
>> On 10/7/2022 12:40 AM, Greg Kroah-Hartman wrote:
>>> On Thu, Oct 06, 2022 at 10:59:51PM -0700, Elliot Berman wrote:
>>>>
>>>> "GH" is the shorthand we've been using for "Gunyah". I didn't find
>>>> documentation for dynamically assigned char devices, but if it exists, I can
>>>> add entry for ttyGH.
>>>
>>> Why use a new name at all? Why not stick with the existing tty names
>>> and device numbers?
>>>
>>
>> I can use hvc framework, although driver-level buffering is needed on
>> both the get_chars/put_chars paths because:
>
> I'm not asking about the framework (although that is a good question,
> you need to document why this has to be new.) I'm asking why pick a new
> name? You will not have a name conflict in your system with this device
> with any other tty name right?
>
That's correct, I didn't see any other instances of "ttyGH" in kernel.
>> - get_chars wants to poll for characters, but Gunyah will push
>> characters to Linux
>> - put_chars can be called in atomic context in the printk console path.
>> Gunyah RM calls can sleep, so we add to buffer and queue work to
>> write the characters.
>>
>> I also chose to use new tty driver because the Gunyah hypervisor call to
>> open the console (gh_rm_console_open) can only be done after starting the
>> VM. Gunyah will only forward characters sent from the other VM to Linux
>> after the gh_rm_console_open call is made. When launching a VM, users would
>> want to open console before VM starts so they can get startup messages from
>> the VM. I planned to use the carrier_raised() to hold
>> tty_port_block_until_ready until the VM is started and the
>> gh_rm_console_open() happens.
>
> I'm sorry, but I don't understand this.
>
> Why is this all a new api at all? What about the virtio api? Why not
> just use that instead?
We want to support virtual machines and Virtual Machine Managers (the
userspace component) that don't support virtio. Qualcomm has some
lightweight VMs that have a Gunyah driver stack but no virtio stack.
Further, implementing a simple userspace VMM to launch a Linux kernel is
much easier with the Gunyah console as no device paravirtualization is
needed to get some output from Linux. I don't anticipate these VMs to be
commonplace, but they do exist.
Thanks,
Elliot
next prev parent reply other threads:[~2022-10-10 20:59 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-28 19:56 [PATCH v4 00/14] Drivers for gunyah hypervisor Elliot Berman
2022-09-28 19:56 ` [PATCH v4 01/14] docs: gunyah: Introduce Gunyah Hypervisor Elliot Berman
2022-09-29 3:43 ` Bagas Sanjaya
2022-09-29 4:02 ` Elliot Berman
2022-09-28 19:56 ` [PATCH v4 02/14] dt-bindings: Add binding for gunyah hypervisor Elliot Berman
2022-09-28 19:56 ` [PATCH v4 03/14] gunyah: Common types and error codes for Gunyah hypercalls Elliot Berman
2022-09-28 19:56 ` [PATCH v4 04/14] arm64: smccc: Include alternative-macros.h Elliot Berman
2022-09-28 19:56 ` [PATCH v4 05/14] virt: gunyah: Add hypercalls to identify Gunyah Elliot Berman
2022-09-28 19:56 ` [PATCH v4 06/14] virt: gunyah: Add sysfs nodes Elliot Berman
2022-09-30 12:09 ` Greg Kroah-Hartman
2022-10-04 23:50 ` Elliot Berman
2022-10-05 6:23 ` Greg Kroah-Hartman
2022-09-28 19:56 ` [PATCH v4 07/14] mailbox: Allow direct registration to a channel Elliot Berman
2022-09-28 19:56 ` [PATCH v4 08/14] virt: gunyah: msgq: Add hypercalls to send and receive messages Elliot Berman
2022-09-28 19:56 ` [PATCH v4 09/14] mailbox: Add Gunyah message queue mailbox Elliot Berman
2022-09-29 16:59 ` Bjorn Andersson
2022-09-29 17:37 ` Jassi Brar
2022-09-28 19:56 ` [PATCH v4 10/14] gunyah: sysfs: Add node to describe supported features Elliot Berman
2022-09-29 7:36 ` Joe Perches
2022-09-29 20:47 ` Elliot Berman
2022-10-02 23:30 ` Jeff Johnson
2022-10-02 23:58 ` Joe Perches
2022-09-30 12:06 ` Greg Kroah-Hartman
2022-10-04 23:53 ` Elliot Berman
2022-09-28 19:56 ` [PATCH v4 11/14] gunyah: rsc_mgr: Add resource manager RPC core Elliot Berman
2022-09-28 19:56 ` [PATCH v4 12/14] gunyah: rsc_mgr: Add RPC for console services Elliot Berman
2022-09-30 12:22 ` Greg Kroah-Hartman
2022-10-03 1:46 ` new checkpatch flexible array test ? (was Re: [PATCH v4 12/14] gunyah: rsc_mgr: Add RPC for console services) Joe Perches
2022-10-03 5:29 ` Greg Kroah-Hartman
2022-10-03 5:38 ` Joe Perches
2022-10-31 18:23 ` Gustavo A. R. Silva
2022-09-28 19:56 ` [PATCH v4 13/14] gunyah: rsc_mgr: Add auxiliary devices for console Elliot Berman
2022-09-30 12:19 ` Greg Kroah-Hartman
2022-10-04 23:49 ` Elliot Berman
2022-10-05 6:21 ` Greg Kroah-Hartman
2022-10-05 21:47 ` Elliot Berman
2022-10-06 6:28 ` Greg Kroah-Hartman
2022-09-28 19:56 ` [PATCH v4 14/14] tty: gunyah: Add tty console driver for RM Console Services Elliot Berman
2022-09-30 12:17 ` Greg Kroah-Hartman
2022-10-07 5:59 ` Elliot Berman
2022-10-07 7:40 ` Greg Kroah-Hartman
2022-10-09 20:59 ` Elliot Berman
2022-10-10 20:23 ` Greg Kroah-Hartman
2022-10-10 20:58 ` Elliot Berman [this message]
2022-10-11 6:22 ` Greg Kroah-Hartman
2022-10-11 22:04 ` Elliot Berman
2022-10-12 6:53 ` Greg Kroah-Hartman
2022-10-08 7:41 ` Zhou Furong
2022-10-08 9:52 ` Greg Kroah-Hartman
2022-10-03 7:01 ` Jiri Slaby
2022-10-10 18:06 ` Elliot Berman
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