From: Alex Elder <elder@linaro.org>
To: Elliot Berman <quic_eberman@quicinc.com>,
Alex Elder <elder@linaro.org>,
Bjorn Andersson <quic_bjorande@quicinc.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Murali Nalajala <quic_mnalajal@quicinc.com>
Cc: 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>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Rob Herring <robh+dt@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
Jonathan Corbet <corbet@lwn.net>,
Bagas Sanjaya <bagasdotme@gmail.com>,
Jassi Brar <jassisinghbrar@gmail.com>,
Sudeep Holla <sudeep.holla@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Lorenzo Pieralisi <lpieralisi@kernel.org>,
Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org
Subject: Re: [PATCH v8 05/28] virt: gunyah: Add hypercalls to identify Gunyah
Date: Tue, 17 Jan 2023 13:20:53 -0600 [thread overview]
Message-ID: <08964d93-8118-1176-c2f8-73e14e022a89@linaro.org> (raw)
In-Reply-To: <4e8a7fdf-8c91-cf2f-d369-c67b7584f580@quicinc.com>
On 1/10/23 11:56 AM, Elliot Berman wrote:
>> Is there any need for the endianness of these values to be specified?
>> Does Gunyah operate with a well-defined endianness? Is there any
>> chance a VM can run with an endianness different from Gunyah? I
>> see that the arm_smcc_* structures are defined without endianness.
>> (Sorry if these are dumb questions.)
>>
>
> All of the data transfers for hypercalls happen via registers, so
> endianness doesn't have impact here (there is no "low address" in a
> register).
I don't believe that is technically true. Practically speaking,
it's probably almost *always* little-endian. But for example,
here:
https://developer.arm.com/documentation/102376/0100/Alignment-and-endianness
it says:
Endianness
In Armv8-A, instruction fetches are always treated as
little-endian.
For data accesses, it is IMPLEMENTATION DEFINED whether
both little-endian and big-endian are supported. And if
only one is supported, it is IMPLEMENTATION DEFINED
which one is supported.
For processors that support both big-endian and
little-endian, endianness is configured per Exception
level.
Perhaps that last sentence doesn't apply to HVC exceptions
but to me it *sounds* like it's at least possible for a VM
to be running with an endianness that differs from the
hypervisor (perhaps not other VMs though.)
This is not an area of expertise of mine, so I would love
for someone who knows more to correct me if I'm wrong.
It's likely to be fine as-is, but (other than the work to
do it and get it right) it doesn't hurt to specify it and
do the conversions as data is passes to/from the hypervisor.
-Alex
next prev parent reply other threads:[~2023-01-17 20:38 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-19 22:58 [PATCH v8 00/28] Drivers for gunyah hypervisor Elliot Berman
2022-12-19 22:58 ` [PATCH v8 01/28] docs: gunyah: Introduce Gunyah Hypervisor Elliot Berman
2023-01-09 21:34 ` Alex Elder
2023-01-10 17:54 ` Elliot Berman
2022-12-19 22:58 ` [PATCH v8 02/28] dt-bindings: Add binding for gunyah hypervisor Elliot Berman
2023-01-09 21:34 ` Alex Elder
2022-12-19 22:58 ` [PATCH v8 03/28] gunyah: Common types and error codes for Gunyah hypercalls Elliot Berman
2023-01-09 21:34 ` Alex Elder
2023-01-10 17:55 ` Elliot Berman
2022-12-19 22:58 ` [PATCH v8 04/28] arm64: smccc: Include alternative-macros.h Elliot Berman
2023-01-09 21:34 ` Alex Elder
2023-01-10 22:55 ` Elliot Berman
2022-12-19 22:58 ` [PATCH v8 05/28] virt: gunyah: Add hypercalls to identify Gunyah Elliot Berman
2023-01-09 21:34 ` Alex Elder
2023-01-10 17:56 ` Elliot Berman
2023-01-17 19:20 ` Alex Elder [this message]
2023-01-17 19:20 ` Alex Elder
2023-01-17 22:29 ` Elliot Berman
2022-12-19 22:58 ` [PATCH v8 06/28] virt: gunyah: Identify hypervisor version Elliot Berman
2023-01-09 21:34 ` Alex Elder
2023-01-10 17:56 ` Elliot Berman
2023-01-17 19:21 ` Alex Elder
2023-01-17 22:29 ` Elliot Berman
2022-12-19 22:58 ` [PATCH v8 07/28] mailbox: Allow direct registration to a channel Elliot Berman
2023-01-09 21:34 ` Alex Elder
2023-01-10 17:57 ` Elliot Berman
2023-01-17 19:21 ` Alex Elder
2022-12-19 22:58 ` [PATCH v8 08/28] virt: gunyah: msgq: Add hypercalls to send and receive messages Elliot Berman
2022-12-19 22:58 ` [PATCH v8 09/28] mailbox: Add Gunyah message queue mailbox Elliot Berman
2023-01-02 6:13 ` Srivatsa Vaddagiri
2023-01-04 0:32 ` Elliot Berman
2023-01-09 21:34 ` Alex Elder
2023-01-10 18:16 ` Elliot Berman
2023-01-17 19:21 ` Alex Elder
2022-12-19 22:58 ` [PATCH v8 10/28] gunyah: rsc_mgr: Add resource manager RPC core Elliot Berman
2023-01-17 22:33 ` Alex Elder
2023-01-20 23:18 ` Elliot Berman
2022-12-19 22:58 ` [PATCH v8 11/28] gunyah: rsc_mgr: Add VM lifecycle RPC Elliot Berman
2023-01-09 7:13 ` Srivatsa Vaddagiri
2023-01-09 18:51 ` Elliot Berman
2023-01-18 18:26 ` Alex Elder
2023-01-20 1:31 ` Elliot Berman
2022-12-19 22:58 ` [PATCH v8 12/28] gunyah: vm_mgr: Introduce basic VM Manager Elliot Berman
2023-01-09 9:05 ` Srivatsa Vaddagiri
2023-01-09 19:38 ` Elliot Berman
2022-12-19 22:58 ` [PATCH v8 13/28] gunyah: rsc_mgr: Add RPC for sharing memory Elliot Berman
2023-01-16 8:45 ` Srivatsa Vaddagiri
2022-12-19 22:58 ` [PATCH v8 14/28] gunyah: vm_mgr: Add/remove user memory regions Elliot Berman
2023-01-20 5:34 ` Srivatsa Vaddagiri
2022-12-19 22:58 ` [PATCH v8 15/28] gunyah: vm_mgr: Add ioctls to support basic non-proxy VM boot Elliot Berman
2022-12-19 22:58 ` [PATCH v8 16/28] samples: Add sample userspace Gunyah VM Manager Elliot Berman
2022-12-19 22:58 ` [PATCH v8 17/28] gunyah: rsc_mgr: Add platform ops on mem_lend/mem_reclaim Elliot Berman
2022-12-19 22:58 ` [PATCH v8 18/28] firmware: qcom_scm: Use fixed width src vm bitmap Elliot Berman
2022-12-19 22:58 ` [PATCH v8 19/28] firmware: qcom_scm: Register Gunyah platform ops Elliot Berman
2022-12-23 17:21 ` kernel test robot
2022-12-19 22:58 ` [PATCH v8 20/28] docs: gunyah: Document Gunyah VM Manager Elliot Berman
2022-12-19 22:58 ` [PATCH v8 21/28] virt: gunyah: Translate gh_rm_hyp_resource into gunyah_resource Elliot Berman
2022-12-19 22:58 ` [PATCH v8 22/28] gunyah: vm_mgr: Add framework to add VM Functions Elliot Berman
2022-12-19 22:58 ` [PATCH v8 23/28] virt: gunyah: Add resource tickets Elliot Berman
2022-12-19 22:58 ` [PATCH v8 24/28] virt: gunyah: Add IO handlers Elliot Berman
2022-12-19 22:58 ` [PATCH v8 25/28] virt: gunyah: Add proxy-scheduled vCPUs Elliot Berman
2022-12-19 22:58 ` [PATCH v8 26/28] virt: gunyah: Add hypercalls for sending doorbell Elliot Berman
2022-12-19 22:58 ` [PATCH v8 27/28] virt: gunyah: Add irqfd interface Elliot Berman
2022-12-21 17:00 ` kernel test robot
2022-12-19 22:58 ` [PATCH v8 28/28] virt: gunyah: Add ioeventfd Elliot Berman
2023-01-09 21:34 ` [PATCH v8 00/28] Drivers for gunyah hypervisor Alex Elder
2023-01-10 17:54 ` Elliot Berman
2023-01-10 21:47 ` Elliot Berman
2023-01-17 19:20 ` Alex Elder
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