[PATCH v14 10/25] gunyah: rsc_mgr: Add RPC for sharing memory
Bjorn Andersson
andersson at kernel.org
Sat Aug 5 10:55:14 PDT 2023
On Tue, Jun 13, 2023 at 10:20:38AM -0700, Elliot Berman wrote:
> Gunyah resource manager provides API to manipulate stage 2 page tables.
> Manipulations are represented as a memory parcel. Memory parcels
> describe a list of memory regions (intermediate physical address--IPA--and
> size), a list of new permissions for VMs, and the memory type (DDR or
> MMIO). Each memory parcel is uniquely identified by a handle allocated by
> Gunyah. There are a few types of memory parcel sharing which Gunyah
> supports:
>
> - Sharing: the guest and host VM both have access
> - Lending: only the guest has access; host VM loses access
> - Donating: Permanently lent (not reclaimed even if guest shuts down)
>
> Memory parcels that have been shared or lent can be reclaimed by the
> host via an additional call. The reclaim operation restores the original
> access the host VM had to the memory parcel and removes the access to
> other VM.
>
> One point to note that memory parcels don't describe where in the guest
> VM the memory parcel should reside. The guest VM must accept the memory
> parcel either explicitly via a "gh_rm_mem_accept" call (not introduced
> here) or be configured to accept it automatically at boot. When the guest
> VM accepts the memory parcel, it also mentions the IPA it wants to place
> memory parcel. Although the region might be discontiguous on the host,
> the memory parcel is place contiguously in the guest memory at the
> specified IPA.
>
> Reviewed-by: Alex Elder <elder at linaro.org>
> Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla at linaro.org>
> Co-developed-by: Prakruthi Deepak Heragu <quic_pheragu at quicinc.com>
> Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu at quicinc.com>
> Signed-off-by: Elliot Berman <quic_eberman at quicinc.com>
> ---
> drivers/virt/gunyah/rsc_mgr_rpc.c | 227 ++++++++++++++++++++++++++++++
> include/linux/gunyah_rsc_mgr.h | 48 +++++++
> 2 files changed, 275 insertions(+)
>
> diff --git a/drivers/virt/gunyah/rsc_mgr_rpc.c b/drivers/virt/gunyah/rsc_mgr_rpc.c
> index a4a9f0ba4e1fc..25064123a31c3 100644
> --- a/drivers/virt/gunyah/rsc_mgr_rpc.c
> +++ b/drivers/virt/gunyah/rsc_mgr_rpc.c
> @@ -6,6 +6,12 @@
> #include <linux/gunyah_rsc_mgr.h>
> #include "rsc_mgr.h"
>
> +/* Message IDs: Memory Management */
> +#define GH_RM_RPC_MEM_LEND 0x51000012
> +#define GH_RM_RPC_MEM_SHARE 0x51000013
> +#define GH_RM_RPC_MEM_RECLAIM 0x51000015
> +#define GH_RM_RPC_MEM_APPEND 0x51000018
> +
> /* Message IDs: VM Management */
> #define GH_RM_RPC_VM_ALLOC_VMID 0x56000001
> #define GH_RM_RPC_VM_DEALLOC_VMID 0x56000002
> @@ -22,6 +28,46 @@ struct gh_rm_vm_common_vmid_req {
> __le16 _padding;
> } __packed;
>
> +/* Call: MEM_LEND, MEM_SHARE */
> +#define GH_MEM_SHARE_REQ_FLAGS_APPEND BIT(1)
> +
> +struct gh_rm_mem_share_req_header {
> + u8 mem_type;
> + u8 _padding0;
> + u8 flags;
> + u8 _padding1;
> + __le32 label;
> +} __packed;
> +
> +struct gh_rm_mem_share_req_acl_section {
> + __le32 n_entries;
> + struct gh_rm_mem_acl_entry entries[];
> +};
> +
> +struct gh_rm_mem_share_req_mem_section {
> + __le16 n_entries;
> + __le16 _padding;
> + struct gh_rm_mem_entry entries[];
> +};
Any reason why these two are not explicitly packed?
> +
> +/* Call: MEM_RELEASE */
> +struct gh_rm_mem_release_req {
> + __le32 mem_handle;
> + u8 flags; /* currently not used */
> + u8 _padding0;
> + __le16 _padding1;
> +} __packed;
> +
> +/* Call: MEM_APPEND */
> +#define GH_MEM_APPEND_REQ_FLAGS_END BIT(0)
> +
> +struct gh_rm_mem_append_req_header {
> + __le32 mem_handle;
> + u8 flags;
> + u8 _padding0;
> + __le16 _padding1;
> +} __packed;
> +
> /* Call: VM_ALLOC */
> struct gh_rm_vm_alloc_vmid_resp {
> __le16 vmid;
> @@ -51,6 +97,8 @@ struct gh_rm_vm_config_image_req {
> __le64 dtb_size;
> } __packed;
>
> +#define GH_RM_MAX_MEM_ENTRIES 512
> +
> /*
> * Several RM calls take only a VMID as a parameter and give only standard
> * response back. Deduplicate boilerplate code by using this common call.
> @@ -64,6 +112,185 @@ static int gh_rm_common_vmid_call(struct gh_rm *rm, u32 message_id, u16 vmid)
> return gh_rm_call(rm, message_id, &req_payload, sizeof(req_payload), NULL, NULL);
> }
>
> +static int _gh_rm_mem_append(struct gh_rm *rm, u32 mem_handle, bool end_append,
> + struct gh_rm_mem_entry *mem_entries, size_t n_mem_entries)
> +{
> + struct gh_rm_mem_share_req_mem_section *mem_section;
"sections" is sufficient.
> + struct gh_rm_mem_append_req_header *req_header;
> + size_t msg_size = 0;
> + void *msg;
> + int ret;
> +
> + msg_size += sizeof(struct gh_rm_mem_append_req_header);
msg_size is sizeof(header) + sizeof(sections), but written this way you
state that it's:
msg_size is X + sizeof(header),
and msg_size is also sizeof(sections)
It's the same thing, but you're forcing the reader to look for the
initial value of msg_size.
> + msg_size += struct_size(mem_section, entries, n_mem_entries);
> +
> + msg = kzalloc(msg_size, GFP_KERNEL);
> + if (!msg)
> + return -ENOMEM;
> +
> + req_header = msg;
Can't you just make msg a strcut gh_rm_mem_append_req_header?
> + mem_section = (void *)(req_header + 1);
> +
> + req_header->mem_handle = cpu_to_le32(mem_handle);
> + if (end_append)
> + req_header->flags |= GH_MEM_APPEND_REQ_FLAGS_END;
> +
> + mem_section->n_entries = cpu_to_le16(n_mem_entries);
> + memcpy(mem_section->entries, mem_entries, sizeof(*mem_entries) * n_mem_entries);
> +
> + ret = gh_rm_call(rm, GH_RM_RPC_MEM_APPEND, msg, msg_size, NULL, NULL);
> + kfree(msg);
> +
> + return ret;
> +}
> +
> +static int gh_rm_mem_append(struct gh_rm *rm, u32 mem_handle,
> + struct gh_rm_mem_entry *mem_entries, size_t n_mem_entries)
You can name these arguments "entries" and "n_entries" (or num_entries)
without loosing any infromation, but saving a whole bunch of characters
that people have to read.
> +{
> + bool end_append;
Iiuc this means "is this the last entry", perhaps calling it "last"
would make its purpose immediately obvious.
> + int ret = 0;
> + size_t n;
> +
> + while (n_mem_entries) {
> + if (n_mem_entries > GH_RM_MAX_MEM_ENTRIES) {
> + end_append = false;
> + n = GH_RM_MAX_MEM_ENTRIES;
> + } else {
> + end_append = true;
> + n = n_mem_entries;
> + }
> +
> + ret = _gh_rm_mem_append(rm, mem_handle, end_append, mem_entries, n);
Every loop here you kzallc() and kfree() the same chunk of scratch
memory. If you inline _gh_rm_mem_append() here and do the allocation
once based on GH_RM_MAX_MEM_ENTRIES this would be faster and seemingly
easier to read/follow.
> + if (ret)
> + break;
> +
> + mem_entries += n;
> + n_mem_entries -= n;
> + }
> +
> + return ret;
> +}
> +
> +static int gh_rm_mem_lend_common(struct gh_rm *rm, u32 message_id, struct gh_rm_mem_parcel *p)
> +{
> + size_t msg_size = 0, initial_mem_entries = p->n_mem_entries, resp_size;
> + size_t acl_section_size, mem_section_size;
You keep all other variables one per line, and in reverse x-mas style.
Please do the same for this.
Naming these acl_size and mem_size would be beneficial.
> + struct gh_rm_mem_share_req_acl_section *acl_section;
> + struct gh_rm_mem_share_req_mem_section *mem_section;
Naming these acl and mem will make below easier to read.
> + struct gh_rm_mem_share_req_header *req_header;
> + u32 *attr_section;
> + __le32 *resp;
> + void *msg;
> + int ret;
> +
> + if (!p->acl_entries || !p->n_acl_entries || !p->mem_entries || !p->n_mem_entries ||
> + p->n_acl_entries > U8_MAX || p->mem_handle != GH_MEM_HANDLE_INVAL)
> + return -EINVAL;
> +
> + if (initial_mem_entries > GH_RM_MAX_MEM_ENTRIES)
> + initial_mem_entries = GH_RM_MAX_MEM_ENTRIES;
> +
> + acl_section_size = struct_size(acl_section, entries, p->n_acl_entries);
> + mem_section_size = struct_size(mem_section, entries, initial_mem_entries);
An empty line here seems reasonable.
> + /* The format of the message goes:
> + * request header
> + * ACL entries (which VMs get what kind of access to this memory parcel)
> + * Memory entries (list of memory regions to share)
> + * Memory attributes (currently unused, we'll hard-code the size to 0)
> + */
> + msg_size += sizeof(struct gh_rm_mem_share_req_header);
Hidden above is the confirmation that msg_size was initialized to 0,
drop the '+' here to make it clear.
> + msg_size += acl_section_size;
> + msg_size += mem_section_size;
> + msg_size += sizeof(u32); /* for memory attributes, currently unused */
> +
> + msg = kzalloc(msg_size, GFP_KERNEL);
> + if (!msg)
> + return -ENOMEM;
> +
> + req_header = msg;
I don't think you need to keep req_header and msg separately.
> + acl_section = (void *)req_header + sizeof(*req_header);
> + mem_section = (void *)acl_section + acl_section_size;
> + attr_section = (void *)mem_section + mem_section_size;
> +
> + req_header->mem_type = p->mem_type;
> + if (initial_mem_entries != p->n_mem_entries)
I think this will only happen if p->n_mem_entries >
GH_RM_MAX_MEM_ENTRIES, for which you already have a condition earlier.
Set the flag in that condition rather than spreading it over two (three)
code paths.
> + req_header->flags |= GH_MEM_SHARE_REQ_FLAGS_APPEND;
> + req_header->label = cpu_to_le32(p->label);
> +
> + acl_section->n_entries = cpu_to_le32(p->n_acl_entries);
> + memcpy(acl_section->entries, p->acl_entries,
> + flex_array_size(acl_section, entries, p->n_acl_entries));
> +
> + mem_section->n_entries = cpu_to_le16(initial_mem_entries);
> + memcpy(mem_section->entries, p->mem_entries,
> + flex_array_size(mem_section, entries, initial_mem_entries));
> +
> + /* Set n_entries for memory attribute section to 0 */
> + *attr_section = 0;
> +
> + ret = gh_rm_call(rm, message_id, msg, msg_size, (void **)&resp, &resp_size);
> + kfree(msg);
> +
> + if (ret)
> + return ret;
> +
> + p->mem_handle = le32_to_cpu(*resp);
> + kfree(resp);
> +
> + if (initial_mem_entries != p->n_mem_entries) {
Another "we took that conditional path above", please make it obvious.
Can you please also write a comment describing that this operation is
split in a main one, followed by one of more appended operations as
necessary. This took me too long time to realize...
In particular I was wondering why "initial" didn't mean "the original
value", but now I see that it probably means "the value relevant for the
initial request".
> + ret = gh_rm_mem_append(rm, p->mem_handle,
> + &p->mem_entries[initial_mem_entries],
> + p->n_mem_entries - initial_mem_entries);
> + if (ret) {
> + gh_rm_mem_reclaim(rm, p);
> + p->mem_handle = GH_MEM_HANDLE_INVAL;
What happens to the entries that was already lended or shared?
Regards,
Bjorn
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