Re: [PATCH v9 10/27] gunyah: rsc_mgr: Add VM lifecycle RPC

[Srinivas Kandagatla <srinivas.kandagatla@linaro.org>]

On 20/01/2023 22:46, Elliot Berman wrote:
> Add Gunyah Resource Manager RPC to launch an unauthenticated VM.
> 
> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
> ---
>   drivers/virt/gunyah/Makefile      |   2 +-
>   drivers/virt/gunyah/rsc_mgr.h     |  36 +++++
>   drivers/virt/gunyah/rsc_mgr_rpc.c | 238 ++++++++++++++++++++++++++++++
>   include/linux/gunyah_rsc_mgr.h    |  55 +++++++
>   4 files changed, 330 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 824749e63a54..2f12f31a2ea6 100644
> --- a/drivers/virt/gunyah/rsc_mgr.h
> +++ b/drivers/virt/gunyah/rsc_mgr.h
> @@ -68,4 +68,40 @@ 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_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_vm_common_vmid_req {
> +	__le16 vmid;
> +	__le16 reserved0;
> +} __packed;
> +
> +/* Call: VM_STOP */
> +struct gh_vm_stop_req {
> +	__le16 vmid;
> +	u8 flags; /* currently not used */
> +	u8 reserved;
> +	__le32 stop_reason; /* currently not used */
> +} __packed;
> +
> +/* Call: VM_CONFIG_IMAGE */
> +struct gh_vm_config_image_req {
> +	__le16 vmid;
> +	__le16 auth_mech;
> +	__le32 mem_handle;
> +	__le64 image_offset;
> +	__le64 image_size;
> +	__le64 dtb_offset;
> +	__le64 dtb_size;
> +} __packed;
> +
> +/* Call: GET_HYP_RESOURCES */
> +
>   #endif
> diff --git a/drivers/virt/gunyah/rsc_mgr_rpc.c b/drivers/virt/gunyah/rsc_mgr_rpc.c
> new file mode 100644
> index 000000000000..b6935dfac1fe
> --- /dev/null
> +++ b/drivers/virt/gunyah/rsc_mgr_rpc.c
> @@ -0,0 +1,238 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#include <linux/gunyah_rsc_mgr.h>
> +
> +#include "rsc_mgr.h"
> +
> +/*
> + * Several RM calls take only a VMID as a parameter and give only standard
> + * response back. Deduplicate boilerplate code by using this common call.
> + */
> +static int gh_rm_common_vmid_call(struct gh_rm *rm, u32 message_id, u16 vmid)
> +{
> +	void *resp;
> +	struct gh_vm_common_vmid_req req_payload = {
> +		.vmid = cpu_to_le16(vmid),
> +	};
> +	size_t resp_size;
> +	int ret;
> +
> +	ret = gh_rm_call(rm, message_id, &req_payload, sizeof(req_payload), &resp, &resp_size);
> +	if (!ret && resp_size) {

Am struggling to understand these type of checks in success case, when a 
command is not expecting any response why are we checking for response 
here, This sounds like a bug in either RM or hypervisor.

Or Is this something that happens due to some firmware behaviour?
Could you elobrate on this.


> +		pr_warn("Unexpected payload size: %ld Expected: 0", resp_size);
> +		dump_stack();
> +		kfree(resp);
> +		return -EBADMSG;
> +	}
> +
> +	return ret;
> +}
> +
> +/**
> + * gh_rm_alloc_vmid() - Allocate a new VM in Gunyah. Returns the VM identifier.
> + * @vmid: Use GH_VMID_INVAL or GH_VMID_SELF (0) to dynamically allocate a VM. A reserved VMID can
> + *        be supplied to request allocation of a platform-defined VM.
> + *
> + * Returns - the allocated VMID or negative value on error
> + */
> +int gh_rm_alloc_vmid(struct gh_rm *rm, u16 vmid)
> +{
> +	void *resp;
> +	struct gh_vm_common_vmid_req req_payload = {
> +		.vmid = cpu_to_le16(vmid),
we pass vmid that is recevied  here.

> +	};
> +	struct gh_vm_alloc_vmid_resp *resp_payload;
> +	size_t resp_size;
> +	int ret;
> +
> +	if (vmid == GH_VMID_INVAL)
> +		vmid = 0;

then we change this to 0.

> +
> +	ret = gh_rm_call(rm, GH_RM_RPC_VM_ALLOC_VMID, &req_payload, sizeof(req_payload), &resp,
> +			&resp_size);
> +	if (ret)
> +		return ret;
> +
> +	if (!vmid) {
then here we check agaist zero.

Why not just do

if (vmid == GH_VMID_INVAL || vmid == GH_VMID_SELF)

this will make core more reader friendly and match to what is in kerneldoc.

> +		if (resp_size != sizeof(*resp_payload)) {
> +			pr_warn("%s: unexpected payload size: %ld Expected: %ld", __func__,
> +				resp_size, sizeof(*resp_payload));
> +			ret = -EBADMSG;
> +		} else {
> +			resp_payload = resp;
> +			ret = le16_to_cpu(resp_payload->vmid);
> +		}
> +	}
> +	kfree(resp);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(gh_rm_alloc_vmid);
> +
> +/**
> + * gh_rm_dealloc_vmid() - Dispose the VMID
> + * @vmid: VM identifier
> + */
> +int gh_rm_dealloc_vmid(struct gh_rm *rm, u16 vmid)
> +{
> +	return gh_rm_common_vmid_call(rm, GH_RM_RPC_VM_DEALLOC_VMID, vmid);
> +}
> +EXPORT_SYMBOL_GPL(gh_rm_dealloc_vmid);
> +
> +/**
> + * gh_rm_vm_start() - Move the VM into "ready to run" state
> + * @vmid: VM identifier
> + *
> + * On VMs which use proxy scheduling, vcpu_run is needed to actually run the VM.
> + * On VMs which use Gunyah's scheduling, the vCPUs start executing in accordance with Gunyah
> + * scheduling policies.
> + */
> +int gh_rm_vm_start(struct gh_rm *rm, u16 vmid)
> +{
> +	return gh_rm_common_vmid_call(rm, GH_RM_RPC_VM_START, vmid);
> +}
> +EXPORT_SYMBOL_GPL(gh_rm_vm_start);
> +
> +/**
> + * gh_rm_vm_stop() - Send a request to Resource Manager VM to stop a VM.
> + * @vmid: VM identifier
> + *
> + * Returns - 0 on success; negative value on failure
> + */
> +int gh_rm_vm_stop(struct gh_rm *rm, u16 vmid)
> +{
> +	struct gh_vm_stop_req req_payload = {
> +		.vmid = cpu_to_le16(vmid),
> +	};
> +	void *resp;
> +	size_t resp_size;
> +	int ret;
> +
> +	ret = gh_rm_call(rm, GH_RM_RPC_VM_STOP, &req_payload, sizeof(req_payload),
> +			&resp, &resp_size);
> +	if (!ret && resp_size) {
same comment as the first one.
> +		pr_warn("%s: unexpected payload size: %ld Expected: 0", __func__, resp_size);
> +		kfree(resp);
> +		return -EBADMSG;
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(gh_rm_vm_stop);
> +
> +int gh_rm_vm_configure(struct gh_rm *rm, u16 vmid, enum gh_rm_vm_auth_mechanism auth_mechanism,
> +		u32 mem_handle, u64 image_offset, u64 image_size, u64 dtb_offset, u64 dtb_size)
> +{
> +	struct gh_vm_config_image_req req_payload = { 0 };
> +	void *resp;
> +	size_t resp_size;
> +	int ret;
> +
> +	req_payload.vmid = cpu_to_le16(vmid);
> +	req_payload.auth_mech = cpu_to_le16(auth_mechanism);
> +	req_payload.mem_handle = cpu_to_le32(mem_handle);
> +	req_payload.image_offset = cpu_to_le64(image_offset);
> +	req_payload.image_size = cpu_to_le64(image_size);
> +	req_payload.dtb_offset = cpu_to_le64(dtb_offset);
> +	req_payload.dtb_size = cpu_to_le64(dtb_size);
> +
> +	ret = gh_rm_call(rm, GH_RM_RPC_VM_CONFIG_IMAGE, &req_payload, sizeof(req_payload),
> +			&resp, &resp_size);
> +	if (!ret && resp_size) {
same comment as the first one.
> +		pr_warn("%s: unexpected payload size: %ld Expected: 0", __func__, resp_size);
> +		kfree(resp);
> +		return -EBADMSG;
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(gh_rm_vm_configure);
> +
> +/**
> + * gh_rm_vm_init() - Move the VM to initialized state.
> + * @vmid: VM identifier
> + *
> + * RM will allocate needed resources for the VM. After gh_rm_vm_init, gh_rm_get_hyp_resources()
> + * can be called to learn of the capabilities we can use with the new VM.
> + *
> + * Returns - 0 on success; negative value on failure
> + */
> +int gh_rm_vm_init(struct gh_rm *rm, u16 vmid)
> +{
> +	return gh_rm_common_vmid_call(rm, GH_RM_RPC_VM_INIT, vmid);
> +}
> +EXPORT_SYMBOL_GPL(gh_rm_vm_init);
> +
> +/**
> + * gh_rm_get_hyp_resources() - Retrieve hypervisor resources (capabilities) associated with a VM
> + * @vmid: VMID of the other VM to get the resources of
> + * @resources: Set by gh_rm_get_hyp_resources and contains the returned hypervisor resources.
> + *
> + * Returns - 0 on success; negative value on failure
> + */
> +int gh_rm_get_hyp_resources(struct gh_rm *rm, u16 vmid,
> +				struct gh_rm_hyp_resources **resources)
> +{
> +	struct gh_rm_hyp_resources *resp;
> +	size_t resp_size;
> +	int ret;
> +	struct gh_vm_common_vmid_req req_payload = {
> +		.vmid = cpu_to_le16(vmid),
> +	};
> +
> +	ret = gh_rm_call(rm, GH_RM_RPC_VM_GET_HYP_RESOURCES,
> +			 &req_payload, sizeof(req_payload),
> +			 (void **)&resp, &resp_size);
we can go upto 100 chars.

> +	if (ret)
> +		return ret;
> +
> +	if (!resp_size)
> +		return -EBADMSG;

This is again another check that falls under the first category, how can 
a command pass and return incorrect responses?

Or are we doing to many unnecessary checks?

> +
> +	if (resp_size < struct_size(resp, entries, 0) ||
> +		resp_size != struct_size(resp, entries, le32_to_cpu(resp->n_entries))) {
> +		kfree(resp);
> +		return -EBADMSG;
> +	}
> +
> +	*resources = resp;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(gh_rm_get_hyp_resources);
> +
> +/**
> + * gh_rm_get_vmid() - Retrieve VMID of this virtual machine
> + * @vmid: Filled with the VMID of this VM
> + */
> +int gh_rm_get_vmid(struct gh_rm *rm, u16 *vmid)
> +{
> +	static u16 cached_vmid = GH_VMID_INVAL;
> +	__le16 *resp;
> +	size_t resp_size;
> +	int ret;
> +
> +	if (cached_vmid != GH_VMID_INVAL) {
> +		*vmid = cached_vmid;
> +		return 0;
> +	}
> +
> +	ret = gh_rm_call(rm, GH_RM_RPC_VM_GET_VMID, NULL, 0, (void **)&resp, &resp_size);
> +	if (ret)
> +		return ret;
> +
> +	if (resp_size != sizeof(*resp)) {
> +		pr_warn("%s: unexpected payload size: %ld Expected: %ld", __func__,
> +			resp_size, sizeof(*resp));
> +		ret = -EBADMSG;
> +		goto out;
> +	}
> +
> +	*vmid = cached_vmid = le16_to_cpu(*resp);
> +out:
> +	kfree(resp);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(gh_rm_get_vmid);