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Message-ID: <deff204d-600a-9606-4f77-85779830f2be@quicinc.com>
Date: Mon, 6 Feb 2023 15:23:42 -0800
From: Elliot Berman <quic_eberman@...cinc.com>
To: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
Bjorn Andersson <quic_bjorande@...cinc.com>,
Alex Elder <elder@...aro.org>,
Murali Nalajala <quic_mnalajal@...cinc.com>
CC: Trilok Soni <quic_tsoni@...cinc.com>,
Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
Carl van Schaik <quic_cvanscha@...cinc.com>,
Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
Arnd Bergmann <arnd@...db.de>,
"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
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>,
Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
Jassi Brar <jassisinghbrar@...il.com>,
Sudeep Holla <sudeep.holla@....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 v9 13/27] gunyah: vm_mgr: Add/remove user memory regions
On 2/6/2023 8:12 AM, Srinivas Kandagatla wrote:
>
>
> 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@...cinc.com>
>> Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>
>> Signed-off-by: Elliot Berman <quic_eberman@...cinc.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(®ion, argp, sizeof(region)))
>> + break;
> Why not be explict about the error codes, do something like.
>
> if (copy_from_user(®ion, argp, sizeof(region)))
> return -EFAULT;
>
>
> setting r value everytime before starting any code is making the code
> more reader unfriendly.
>
>
Done.
>> +
>> + 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.
>
This behavior is described in "Document Gunyah VM Manager":
https://lore.kernel.org/all/20230120224627.4053418-20-quic_eberman@quicinc.com/
>> + r = 0;
>> + mapping = gh_vm_mem_mapping_alloc(ghvm, ®ion);
>> + 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.
Done.
>> + 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?
>
Neither, it's used in vm_mgr.c.
>> + 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.
>
Done, and checked throughout the series as well.
>> + if (!region->memory_size || !PAGE_ALIGNED(region->memory_size) ||
>> + !PAGE_ALIGNED(region->userspace_addr))
> Even this alignment needs some documentation.
>
Documented now.
> Or why not just let the user only pass number of pages instead of size?
>
>
KVM, Nitro enclaves, and ACRN all give size directly and not as # of pages.
>> + 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.
>
Done.
>
>> +
>> + 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?
>
The label is unique and userspace is aware of this. One userspace owns
the VM FD.
>
>> + 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?
>
In all our use cases so far, only a few (max 3) mappings are used.
Gunyah and Linux would be similarly bounded by heap-based memory
constraints when adding more memory mappings if you don't hit U32_MAX first.
This could be reworked into a rb tree, but I thought it better to use a
simpler list-based implementation since it was easier to review and
benefits are not seen when only a few mappings used.
[snip]
>> --- 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.
>
Done, as well for the other UAPI structs added later in the series.
>> + __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
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