Re: [PATCH v9 13/27] gunyah: vm_mgr: Add/remove user memory regions

Srinivas Kandagatla
2023-02-06T16:13:40Z

On 20/01/2023 22:46, Elliot Berman wrote:
> When launching a virtual machine, Gunyah userspace allocates memory for
> the guest and informs Gunyah about these memory regions through
> SET_USER_MEMORY_REGION ioctl.
>
> Co-developed-by: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
> Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
> Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
> ---
> drivers/virt/gunyah/Makefile | 2 +-
> drivers/virt/gunyah/vm_mgr.c | 46 +++++++
> drivers/virt/gunyah/vm_mgr.h | 28 +++-
> drivers/virt/gunyah/vm_mgr_mm.c | 223 ++++++++++++++++++++++++++++++++
> include/uapi/linux/gunyah.h | 22 ++++
> 5 files changed, 319 insertions(+), 2 deletions(-)
> create mode 100644 drivers/virt/gunyah/vm_mgr_mm.c
>
> diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
> index 03951cf82023..ff8bc4925392 100644
> --- a/drivers/virt/gunyah/Makefile
> +++ b/drivers/virt/gunyah/Makefile
> @@ -2,5 +2,5 @@
>
> obj-$(CONFIG_GUNYAH) += gunyah.o
>
> -gunyah_rsc_mgr-y += rsc_mgr.o rsc_mgr_rpc.o vm_mgr.o
> +gunyah_rsc_mgr-y += rsc_mgr.o rsc_mgr_rpc.o vm_mgr.o vm_mgr_mm.o
> obj-$(CONFIG_GUNYAH) += gunyah_rsc_mgr.o
> diff --git a/drivers/virt/gunyah/vm_mgr.c b/drivers/virt/gunyah/vm_mgr.c
> index 0864dbd77e28..b847fde63333 100644
> --- a/drivers/virt/gunyah/vm_mgr.c
> +++ b/drivers/virt/gunyah/vm_mgr.c
> @@ -35,14 +35,55 @@ static __must_check struct gunyah_vm *gunyah_vm_alloc(struct gh_rm_rpc *rm)
> ghvm->vmid = vmid;
> ghvm->rm = rm;
>
> + mutex_init(&ghvm->mm_lock);
> + INIT_LIST_HEAD(&ghvm->memory_mappings);
> +
> return ghvm;
> }
>
> static long gh_vm_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> {
> + struct gunyah_vm *ghvm = filp->private_data;
> + void __user *argp = (void __user *)arg;
> long r;
>
> switch (cmd) {
> + case GH_VM_SET_USER_MEM_REGION: {
> + struct gunyah_vm_memory_mapping *mapping;
> + struct gh_userspace_memory_region region;
> +
> + r = -EFAULT;
> + if (copy_from_user(&region, argp, sizeof(region)))
> + break;
Why not be explict about the error codes, do something like.

if (copy_from_user(&region, argp, sizeof(region)))
return -EFAULT;

setting r value everytime before starting any code is making the code
more reader unfriendly.

> +
> + r = -EINVAL;
> + /* All other flag bits are reserved for future use */
> + if (region.flags & ~(GH_MEM_ALLOW_READ | GH_MEM_ALLOW_WRITE | GH_MEM_ALLOW_EXEC |
> + GH_MEM_LENT))
> + break;
> +
> +
> + if (region.memory_size) {

This behaviour allocating memory in presense of valid memory_size and
finding memory in cases of zero size needs to be described properly in
the uapi so that the users are aware of this.

> + r = 0;
> + mapping = gh_vm_mem_mapping_alloc(ghvm, &region);
> + if (IS_ERR(mapping)) {
> + r = PTR_ERR(mapping);
> + break;
> + }
> + } else {
> + mapping = gh_vm_mem_mapping_find(ghvm, region.label);
> + if (IS_ERR(mapping)) {
> + r = PTR_ERR(mapping);
> + break;
> + }
> + r = 0;
> + if (!mapping)
> + break;
> + gh_vm_mem_mapping_reclaim(ghvm, mapping);
> + kfree(mapping);
> + }
> + break;
> + }
> default:
> r = -ENOTTY;
> break;
> @@ -54,7 +95,12 @@ static long gh_vm_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> static int gh_vm_release(struct inode *inode, struct file *filp)
> {
> struct gunyah_vm *ghvm = filp->private_data;
> + struct gunyah_vm_memory_mapping *mapping, *tmp;
>
Locking?
> + list_for_each_entry_safe(mapping, tmp, &ghvm->memory_mappings, list) {
> + gh_vm_mem_mapping_reclaim(ghvm, mapping);
> + kfree(mapping);
> + }
> put_gh_rm(ghvm->rm);
> kfree(ghvm);
> return 0;
> diff --git a/drivers/virt/gunyah/vm_mgr.h b/drivers/virt/gunyah/vm_mgr.h
> index e47f34de7f9e..6b38bf780f76 100644
> --- a/drivers/virt/gunyah/vm_mgr.h
> +++ b/drivers/virt/gunyah/vm_mgr.h
> @@ -7,14 +7,40 @@
> #define _GH_PRIV_VM_MGR_H
>
> #include <linux/gunyah_rsc_mgr.h>
> +#include <linux/list.h>
> +#include <linux/miscdevice.h>
> +#include <linux/mutex.h>
>
> #include <uapi/linux/gunyah.h>
>
> long gh_dev_vm_mgr_ioctl(struct gh_rm *rm, unsigned int cmd, unsigned long arg);
>
> +enum gunyah_vm_mem_share_type {
> + VM_MEM_SHARE,
> + VM_MEM_LEND,
> +};
> +
> +struct gunyah_vm_memory_mapping {
> + struct list_head list;
> + enum gunyah_vm_mem_share_type share_type;
> + struct gh_rm_mem_parcel parcel;
> +
> + __u64 guest_phys_addr;
> + struct page **pages;
> + unsigned long npages;
> +};
> +
> struct gunyah_vm {
> u16 vmid;
> - struct gh_rm_rpc *rm;
> + struct gh_rm *rm;
> +
> + struct mutex mm_lock;
> + struct list_head memory_mappings;
> };
>
> +struct gunyah_vm_memory_mapping *gh_vm_mem_mapping_alloc(struct gunyah_vm *ghvm,
> + struct gh_userspace_memory_region *region);
> +void gh_vm_mem_mapping_reclaim(struct gunyah_vm *ghvm, struct gunyah_vm_memory_mapping *mapping);
> +struct gunyah_vm_memory_mapping *gh_vm_mem_mapping_find(struct gunyah_vm *ghvm, u32 label);
> +
> #endif
> diff --git a/drivers/virt/gunyah/vm_mgr_mm.c b/drivers/virt/gunyah/vm_mgr_mm.c
> new file mode 100644
> index 000000000000..f2dbdb4ee8ab
> --- /dev/null
> +++ b/drivers/virt/gunyah/vm_mgr_mm.c
> @@ -0,0 +1,223 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#define pr_fmt(fmt) "gh_vm_mgr: " fmt
> +
> +#include <linux/gunyah_rsc_mgr.h>
> +#include <linux/mm.h>
> +
> +#include <uapi/linux/gunyah.h>
> +
> +#include "vm_mgr.h"
> +
> +static inline bool page_contiguous(phys_addr_t p, phys_addr_t t)
> +{
> + return t - p == PAGE_SIZE;
> +}
> +
> +static struct gunyah_vm_memory_mapping *__gh_vm_mem_mapping_find(struct gunyah_vm *ghvm, u32 label)
> +{
> + struct gunyah_vm_memory_mapping *mapping;
> +
> +
only one line.
> + list_for_each_entry(mapping, &ghvm->memory_mappings, list)
> + if (mapping->parcel.label == label)
> + return mapping;
> +
> + return NULL;
> +}
> +
> +void gh_vm_mem_mapping_reclaim(struct gunyah_vm *ghvm, struct gunyah_vm_memory_mapping *mapping)
> +{
> + int i, ret = 0;
> +
> + if (mapping->parcel.mem_handle != GH_MEM_HANDLE_INVAL) {
> + ret = gh_rm_mem_reclaim(ghvm->rm, &mapping->parcel);
> + if (ret)
> + pr_warn("Failed to reclaim memory parcel for label %d: %d\n",
> + mapping->parcel.label, ret);
> + }
> +
> + if (!ret)
> + for (i = 0; i < mapping->npages; i++)
> + unpin_user_page(mapping->pages[i]);
> +
> + kfree(mapping->pages);
> + kfree(mapping->parcel.acl_entries);
> + kfree(mapping->parcel.mem_entries);
> +
> + mutex_lock(&ghvm->mm_lock);
> + list_del(&mapping->list);
> + mutex_unlock(&ghvm->mm_lock);
> +}
> +
> +struct gunyah_vm_memory_mapping *gh_vm_mem_mapping_find(struct gunyah_vm *ghvm, u32 label)
> +{
> + struct gunyah_vm_memory_mapping *mapping;
> + int ret;
> +
> + ret = mutex_lock_interruptible(&ghvm->mm_lock);
> + if (ret)
> + return ERR_PTR(ret);
> + mapping = __gh_vm_mem_mapping_find(ghvm, label);
> + mutex_unlock(&ghvm->mm_lock);
> + return mapping ? : ERR_PTR(-ENODEV);
> +}
> +
> +struct gunyah_vm_memory_mapping *gh_vm_mem_mapping_alloc(struct gunyah_vm *ghvm,
> + struct gh_userspace_memory_region *region)
> +{
Is this a static functoin or an exported symbol?

> + phys_addr_t curr_page, prev_page;
> + struct gunyah_vm_memory_mapping *mapping, *tmp_mapping;
> + struct gh_rm_mem_entry *mem_entries;
> + int i, j, pinned, ret = 0;
> + struct gh_rm_mem_parcel *parcel;
> + size_t entry_size;
> + u16 vmid; > +
Reverse christmas tree to sor local variables would be nice.

> + if (!region->memory_size || !PAGE_ALIGNED(region->memory_size) ||
> + !PAGE_ALIGNED(region->userspace_addr))
Even this alignment needs some documentation.

Or why not just let the user only pass number of pages instead of size?

> + return ERR_PTR(-EINVAL);
> +
> + if (!gh_api_has_feature(GH_API_FEATURE_MEMEXTENT))
> + return ERR_PTR(-EOPNOTSUPP);

We should proabably move this as very first check while handling this IOCTL.

> +
> + ret = mutex_lock_interruptible(&ghvm->mm_lock);
> + if (ret)
> + return ERR_PTR(ret);
> + mapping = __gh_vm_mem_mapping_find(ghvm, region->label);

so label is unique and userspace proabably aware of this?
Can we have more than one userspace doing this? and if so how can it
ensure that each label is unique?

> + if (mapping) {
> + mutex_unlock(&ghvm->mm_lock);
> + return ERR_PTR(-EEXIST);
> + }
> +
> + mapping = kzalloc(sizeof(*mapping), GFP_KERNEL);
> + if (!mapping) {
> + ret = -ENOMEM;
> + goto unlock;
> + }
> +
> + mapping->parcel.label = region->label;

> + mapping->guest_phys_addr = region->guest_phys_addr;
> + mapping->npages = region->memory_size >> PAGE_SHIFT;
> + parcel = &mapping->parcel;
> + parcel->mem_handle = GH_MEM_HANDLE_INVAL; /* to be filled later by mem_share/mem_lend */
> + parcel->mem_type = GH_RM_MEM_TYPE_NORMAL;
> +
> + /* Check for overlap */
> + list_for_each_entry(tmp_mapping, &ghvm->memory_mappings, list) {
> + if (!((mapping->guest_phys_addr + (mapping->npages << PAGE_SHIFT) <=
> + tmp_mapping->guest_phys_addr) ||
> + (mapping->guest_phys_addr >=
> + tmp_mapping->guest_phys_addr + (tmp_mapping->npages << PAGE_SHIFT)))) {
> + ret = -EEXIST;
> + goto unlock;
> + }
> + }
This looks like we will loop every mappign for each allocation giving us
an O(n), How frequent and how many max mappings can be there in the system?

> +
> + list_add(&mapping->list, &ghvm->memory_mappings);
> +unlock:
> + mutex_unlock(&ghvm->mm_lock);
> + if (ret)
> + goto free_mapping;
> +
> + mapping->pages = kcalloc(mapping->npages, sizeof(*mapping->pages), GFP_KERNEL);
> + if (!mapping->pages) {
> + ret = -ENOMEM;
> + goto reclaim;
> + }
> +
> + pinned = pin_user_pages_fast(region->userspace_addr, mapping->npages,
> + FOLL_WRITE | FOLL_LONGTERM, mapping->pages);
> + if (pinned < 0) {
> + ret = pinned;
> + goto reclaim;
> + } else if (pinned != mapping->npages) {
> + ret = -EFAULT;
> + mapping->npages = pinned; /* update npages for reclaim */
> + goto reclaim;
> + }
> +
> + if (region->flags & GH_MEM_LENT) {
> + parcel->n_acl_entries = 1;
> + mapping->share_type = VM_MEM_LEND;
> + } else {
> + parcel->n_acl_entries = 2;
> + mapping->share_type = VM_MEM_SHARE;
> + }
> + parcel->acl_entries = kcalloc(parcel->n_acl_entries,
> + sizeof(*parcel->acl_entries),
> + GFP_KERNEL);
> + if (!parcel->acl_entries) {
> + ret = -ENOMEM;
> + goto reclaim;
> + }
> +
> + parcel->acl_entries[0].vmid = cpu_to_le16(ghvm->vmid);
> + if (region->flags & GH_MEM_ALLOW_READ)
> + parcel->acl_entries[0].perms |= GH_RM_ACL_R;
> + if (region->flags & GH_MEM_ALLOW_WRITE)
> + parcel->acl_entries[0].perms |= GH_RM_ACL_W;
> + if (region->flags & GH_MEM_ALLOW_EXEC)
> + parcel->acl_entries[0].perms |= GH_RM_ACL_X;
> +
> + if (mapping->share_type == VM_MEM_SHARE) {
> + ret = gh_rm_get_vmid(ghvm->rm, &vmid);
> + if (ret) {
> + if (ret > 0) {
> + pr_warn("RM failed to get this VM's VMID: %d", ret);
> + ret = -EINVAL;
> + }
> + goto reclaim;
> + }
> +
> + parcel->acl_entries[1].vmid = cpu_to_le16(vmid);
> + /* Host assumed to have all these permissions. Gunyah will not
> + * grant new permissions if host actually had less than RWX
> + */
> + parcel->acl_entries[1].perms |= GH_RM_ACL_R | GH_RM_ACL_W | GH_RM_ACL_X;
> + }
> +
> + mem_entries = kcalloc(mapping->npages, sizeof(*mem_entries), GFP_KERNEL);
> + if (!mem_entries) {
> + ret = -ENOMEM;
> + goto reclaim;
> + }
> +
> + /* reduce number of entries by combining contiguous pages into single memory entry */
> + prev_page = page_to_phys(mapping->pages[0]);
> + mem_entries[0].ipa_base = cpu_to_le64(prev_page);
> + entry_size = PAGE_SIZE;
> + for (i = 1, j = 0; i < mapping->npages; i++) {
> + curr_page = page_to_phys(mapping->pages[i]);
> + if (page_contiguous(prev_page, curr_page)) {
> + entry_size += PAGE_SIZE;
> + } else {
> + mem_entries[j].size = cpu_to_le64(entry_size);
> + j++;
> + mem_entries[j].ipa_base = cpu_to_le64(curr_page);
> + entry_size = PAGE_SIZE;
> + }
> +
> + prev_page = curr_page;
> + }
> + mem_entries[j].size = cpu_to_le64(entry_size);
> +
> + parcel->n_mem_entries = j + 1;
> + parcel->mem_entries = kmemdup(mem_entries, sizeof(*mem_entries) * parcel->n_mem_entries,
> + GFP_KERNEL);
> + kfree(mem_entries);
> + if (!parcel->mem_entries) {
> + ret = -ENOMEM;
> + goto reclaim;
> + }
> +
> + return mapping;
> +reclaim:
> + gh_vm_mem_mapping_reclaim(ghvm, mapping);
> +free_mapping:
> + kfree(mapping);
> + return ERR_PTR(ret);
> +}
> diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
> index 88a40d6e0b96..574f33b198d0 100644
> --- a/include/uapi/linux/gunyah.h
> +++ b/include/uapi/linux/gunyah.h
> @@ -20,4 +20,26 @@
> */
> #define GH_CREATE_VM _IO(GH_IOCTL_TYPE, 0x0) /* Returns a Gunyah VM fd */
>
> +/*
> + * ioctls for VM fds
> + */
> +struct gh_userspace_memory_region {

This struct needs some kernedoc.

> + __u32 label;

> +#define GH_MEM_ALLOW_READ (1UL << 0)
> +#define GH_MEM_ALLOW_WRITE (1UL << 1)
> +#define GH_MEM_ALLOW_EXEC (1UL << 2)
> +/*
> + * The guest will be lent the memory instead of shared.
> + * In other words, the guest has exclusive access to the memory region and the host loses access.
> + */
> +#define GH_MEM_LENT (1UL << 3)
> + __u32 flags;
> + __u64 guest_phys_addr;
> + __u64 memory_size;
if we are only expecting pages, this should probably be make explict by
using nr_pages instead of size

> + __u64 userspace_addr;
> +};
> +
> +#define GH_VM_SET_USER_MEM_REGION _IOW(GH_IOCTL_TYPE, 0x1, \
> + struct gh_userspace_memory_region)
> +
> #endif