Re: [PATCH v14 15/25] virt: gunyah: Add Qualcomm Gunyah platform ops

[Bjorn Andersson]

On Tue, Jun 13, 2023 at 10:20:43AM -0700, Elliot Berman wrote:
> Qualcomm platforms have a firmware entity which performs access control
> to physical pages. Dynamically started Gunyah virtual machines use the
> QCOM_SCM_RM_MANAGED_VMID for access. Linux thus needs to assign access
> to the memory used by guest VMs. Gunyah doesn't do this operation for us
> since it is the current VM (typically VMID_HLOS) delegating the access
> and not Gunyah itself. Use the Gunyah platform ops to achieve this so
> that only Qualcomm platforms attempt to make the needed SCM calls.
> 
> Reviewed-by: Alex Elder <elder@xxxxxxxxxx>
> Co-developed-by: Prakruthi Deepak Heragu <quic_pheragu@xxxxxxxxxxx>
> Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@xxxxxxxxxxx>
> Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
> ---
>  drivers/virt/gunyah/Kconfig       |  13 +++
>  drivers/virt/gunyah/Makefile      |   1 +
>  drivers/virt/gunyah/gunyah_qcom.c | 153 ++++++++++++++++++++++++++++++
>  3 files changed, 167 insertions(+)
>  create mode 100644 drivers/virt/gunyah/gunyah_qcom.c
> 
> diff --git a/drivers/virt/gunyah/Kconfig b/drivers/virt/gunyah/Kconfig
> index de815189dab6c..0421b751aad4f 100644
> --- a/drivers/virt/gunyah/Kconfig
> +++ b/drivers/virt/gunyah/Kconfig
> @@ -5,6 +5,7 @@ config GUNYAH
>  	depends on ARM64
>  	depends on MAILBOX
>  	select GUNYAH_PLATFORM_HOOKS
> +	imply GUNYAH_QCOM_PLATFORM if ARCH_QCOM
>  	help
>  	  The Gunyah drivers are the helper interfaces that run in a guest VM
>  	  such as basic inter-VM IPC and signaling mechanisms, and higher level
> @@ -15,3 +16,15 @@ config GUNYAH
>  
>  config GUNYAH_PLATFORM_HOOKS
>  	tristate
> +
> +config GUNYAH_QCOM_PLATFORM
> +	tristate "Support for Gunyah on Qualcomm platforms"
> +	depends on GUNYAH
> +	select GUNYAH_PLATFORM_HOOKS
> +	select QCOM_SCM
> +	help
> +	  Enable support for interacting with Gunyah on Qualcomm
> +	  platforms. Interaction with Qualcomm firmware requires
> +	  extra platform-specific support.
> +
> +	  Say Y/M here to use Gunyah on Qualcomm platforms.
> diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
> index 4fbeee521d60a..2aa9ff038ed02 100644
> --- a/drivers/virt/gunyah/Makefile
> +++ b/drivers/virt/gunyah/Makefile
> @@ -1,6 +1,7 @@
>  # SPDX-License-Identifier: GPL-2.0
>  
>  obj-$(CONFIG_GUNYAH_PLATFORM_HOOKS) += gunyah_platform_hooks.o
> +obj-$(CONFIG_GUNYAH_QCOM_PLATFORM) += gunyah_qcom.o
>  
>  gunyah-y += rsc_mgr.o rsc_mgr_rpc.o vm_mgr.o vm_mgr_mm.o
>  obj-$(CONFIG_GUNYAH) += gunyah.o
> diff --git a/drivers/virt/gunyah/gunyah_qcom.c b/drivers/virt/gunyah/gunyah_qcom.c
> new file mode 100644
> index 0000000000000..f06a598f2e1b3
> --- /dev/null
> +++ b/drivers/virt/gunyah/gunyah_qcom.c
> @@ -0,0 +1,153 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/gunyah_rsc_mgr.h>
> +#include <linux/module.h>
> +#include <linux/firmware/qcom/qcom_scm.h>
> +#include <linux/types.h>
> +#include <linux/uuid.h>
> +
> +#define QCOM_SCM_RM_MANAGED_VMID	0x3A
> +#define QCOM_SCM_MAX_MANAGED_VMID	0x3F
> +
> +static int qcom_scm_gh_rm_pre_mem_share(struct gh_rm *rm, struct gh_rm_mem_parcel *mem_parcel)
> +{
> +	struct qcom_scm_vmperm *new_perms;
> +	u64 src, src_cpy;
> +	int ret = 0, i, n;
> +	u16 vmid;
> +
> +	new_perms = kcalloc(mem_parcel->n_acl_entries, sizeof(*new_perms), GFP_KERNEL);
> +	if (!new_perms)
> +		return -ENOMEM;
> +
> +	for (n = 0; n < mem_parcel->n_acl_entries; n++) {
> +		vmid = le16_to_cpu(mem_parcel->acl_entries[n].vmid);
> +		if (vmid <= QCOM_SCM_MAX_MANAGED_VMID)
> +			new_perms[n].vmid = vmid;
> +		else
> +			new_perms[n].vmid = QCOM_SCM_RM_MANAGED_VMID;
> +		if (mem_parcel->acl_entries[n].perms & GH_RM_ACL_X)
> +			new_perms[n].perm |= QCOM_SCM_PERM_EXEC;
> +		if (mem_parcel->acl_entries[n].perms & GH_RM_ACL_W)
> +			new_perms[n].perm |= QCOM_SCM_PERM_WRITE;
> +		if (mem_parcel->acl_entries[n].perms & GH_RM_ACL_R)
> +			new_perms[n].perm |= QCOM_SCM_PERM_READ;
> +	}
> +
> +	src = BIT_ULL(QCOM_SCM_VMID_HLOS);
> +
> +	for (i = 0; i < mem_parcel->n_mem_entries; i++) {
> +		src_cpy = src;
> +		ret = qcom_scm_assign_mem(le64_to_cpu(mem_parcel->mem_entries[i].phys_addr),
> +						le64_to_cpu(mem_parcel->mem_entries[i].size),
> +						&src_cpy, new_perms, mem_parcel->n_acl_entries);
> +		if (ret)
> +			break;
> +	}
> +
> +	if (!ret)
> +		goto out;

I was going to complain that you don't unroll the assignments on
failure, but now realized that this "error handling" is backwards and
actually represents the success case.

Please don't do that, goto error_handling || kfree(new_perms); return 0;
here instead.


That also means that you don't need to zero-initialize ret, because you
would goto err_reclaim inside the loop.

> +
> +	src = 0;
> +	for (n = 0; n < mem_parcel->n_acl_entries; n++) {
> +		vmid = le16_to_cpu(mem_parcel->acl_entries[n].vmid);
> +		if (vmid <= QCOM_SCM_MAX_MANAGED_VMID)
> +			src |= BIT_ULL(vmid);
> +		else
> +			src |= BIT_ULL(QCOM_SCM_RM_MANAGED_VMID);
> +	}
> +
> +	new_perms[0].vmid = QCOM_SCM_VMID_HLOS;
> +
> +	for (i--; i >= 0; i--) {
> +		src_cpy = src;
> +		WARN_ON_ONCE(qcom_scm_assign_mem(
> +				le64_to_cpu(mem_parcel->mem_entries[i].phys_addr),
> +				le64_to_cpu(mem_parcel->mem_entries[i].size),
> +				&src_cpy, new_perms, 1));
> +	}
> +
> +out:
> +	kfree(new_perms);
> +	return ret;
> +}

Regards,
Bjorn