linux-kernel - Re: [PATCH v10 09/26] gunyah: rsc

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Date:   Thu, 16 Feb 2023 09:18:13 -0800
From:   Elliot Berman <quic_eberman@...cinc.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Alex Elder <elder@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
        Murali Nalajala <quic_mnalajal@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
        Carl van Schaik <quic_cvanscha@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        "Arnd Bergmann" <arnd@...db.de>, Rob Herring <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        Jonathan Corbet <corbet@....net>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Jassi Brar <jassisinghbrar@...il.com>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v10 09/26] gunyah: rsc_mgr: Add VM lifecycle RPC



On 2/15/2023 10:39 PM, Greg Kroah-Hartman wrote:
> On Tue, Feb 14, 2023 at 01:23:42PM -0800, Elliot Berman wrote:
>>
>> Add Gunyah Resource Manager RPC to launch an unauthenticated VM.
>>
>> Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>
>> ---
>>   drivers/virt/gunyah/Makefile      |   2 +-
>>   drivers/virt/gunyah/rsc_mgr.h     |  45 ++++++
>>   drivers/virt/gunyah/rsc_mgr_rpc.c | 226 ++++++++++++++++++++++++++++++
>>   include/linux/gunyah_rsc_mgr.h    |  73 ++++++++++
>>   4 files changed, 345 insertions(+), 1 deletion(-)
>>   create mode 100644 drivers/virt/gunyah/rsc_mgr_rpc.c
>>
>> diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
>> index cc864ff5abbb..de29769f2f3f 100644
>> --- a/drivers/virt/gunyah/Makefile
>> +++ b/drivers/virt/gunyah/Makefile
>> @@ -2,5 +2,5 @@
>>   
>>   obj-$(CONFIG_GUNYAH) += gunyah.o
>>   
>> -gunyah_rsc_mgr-y += rsc_mgr.o
>> +gunyah_rsc_mgr-y += rsc_mgr.o rsc_mgr_rpc.o
>>   obj-$(CONFIG_GUNYAH) += gunyah_rsc_mgr.o
>> diff --git a/drivers/virt/gunyah/rsc_mgr.h b/drivers/virt/gunyah/rsc_mgr.h
>> index d4e799a7526f..7406237bc66d 100644
>> --- a/drivers/virt/gunyah/rsc_mgr.h
>> +++ b/drivers/virt/gunyah/rsc_mgr.h
>> @@ -74,4 +74,49 @@ struct gh_rm;
>>   int gh_rm_call(struct gh_rm *rsc_mgr, u32 message_id, void *req_buff, size_t req_buff_size,
>>   		void **resp_buf, size_t *resp_buff_size);
>>   
>> +/* Message IDs: VM Management */
>> +#define GH_RM_RPC_VM_ALLOC_VMID			0x56000001
>> +#define GH_RM_RPC_VM_DEALLOC_VMID		0x56000002
>> +#define GH_RM_RPC_VM_START			0x56000004
>> +#define GH_RM_RPC_VM_STOP			0x56000005
>> +#define GH_RM_RPC_VM_RESET			0x56000006
>> +#define GH_RM_RPC_VM_CONFIG_IMAGE		0x56000009
>> +#define GH_RM_RPC_VM_INIT			0x5600000B
>> +#define GH_RM_RPC_VM_GET_HYP_RESOURCES		0x56000020
>> +#define GH_RM_RPC_VM_GET_VMID			0x56000024
>> +
>> +struct gh_rm_vm_common_vmid_req {
>> +	__le16 vmid;
>> +	__le16 reserved0;
> 
> reserved for what?  What is a valid value for this field?  Should it be
> checked for 0?

This struct is transmitted "over the wire" and RM makes all of its 
structures 4-byte aligned. The reserved fields are padding for this 
alignment and will be zero but don't need to be checked. Linux 
initializes the reserved fields to zero.

> 
> Same with other "reserved0" fields in this file.
> 
> 
>> +} __packed;
>> +
>> +/* Call: VM_ALLOC */
>> +struct gh_rm_vm_alloc_vmid_resp {
>> +	__le16 vmid;
>> +	__le16 reserved0;
>> +} __packed;
>> +
>> +/* Call: VM_STOP */
>> +struct gh_rm_vm_stop_req {
>> +	__le16 vmid;
>> +#define GH_RM_VM_STOP_FLAG_FORCE_STOP	BIT(0)
>> +	u8 flags;
>> +	u8 reserved;
> 
> Why just "reserved" and not "reserved0"?  Naming is hard :(
> 

Some fields have multiple reserved fields. I'll clean up so "reserved0" 
only appears when there are multiple padding fields.

Thanks,
Elliot