Re: [PATCH v3 1/4] nitro_enclaves: Merge contiguous physical memory regions

[Paraschiv, Andra-Irina]

On 09/10/2021 04:32, Longpeng(Mike) wrote:
> From: Longpeng <longpeng2@xxxxxxxxxx>
>
> There can be cases when there are more memory regions that need to be
> set for an enclave than the maximum supported number of memory regions
> per enclave. One example can be when the memory regions are backed by 2
> MiB hugepages (the minimum supported hugepage size).
>
> Let's merge the adjacent regions if they are physical contiguous. This

physical contiguous => physically contiguous

> way the final number of memory regions is less than before merging and
> could potentially avoid reaching maximum.
>
> Signed-off-by: Longpeng <longpeng2@xxxxxxxxxx>
> ---
> Changes v2 -> v3:
>    - update the commit title and commit message.  [Andra]
>    - use 'struct range' to instead of 'struct phys_mem_region'.  [Andra, Greg KH]
>    - add comments before the function definition.  [Andra]
>    - rename several variables, parameters and function.  [Andra]
> ---
>   drivers/virt/nitro_enclaves/ne_misc_dev.c | 79 +++++++++++++++++++++----------
>   1 file changed, 55 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/virt/nitro_enclaves/ne_misc_dev.c b/drivers/virt/nitro_enclaves/ne_misc_dev.c
> index e21e1e8..eea53e9 100644
> --- a/drivers/virt/nitro_enclaves/ne_misc_dev.c
> +++ b/drivers/virt/nitro_enclaves/ne_misc_dev.c
> @@ -26,6 +26,7 @@
>   #include <linux/poll.h>
>   #include <linux/slab.h>
>   #include <linux/types.h>
> +#include <linux/range.h>

Please keep the alphabetical order and move this before "#include 
<linux/slab.h>."

>   #include <uapi/linux/vm_sockets.h>
>
>   #include "ne_misc_dev.h"
> @@ -126,6 +127,16 @@ struct ne_cpu_pool {
>   static struct ne_cpu_pool ne_cpu_pool;
>
>   /**
> + * struct phys_contig_mem_regions - Physical contiguous memory regions

Physical contiguous memory regions => Contiguous physical memory regions

> + * @num:       The number of regions that currently has.
> + * @region:    The array of physical memory regions.
> + */
> +struct phys_contig_mem_regions {
> +       unsigned long num;
> +       struct range region[0];

Should use "struct range *regions" instead, to keep a similar style with 
regard to arrays throughout the code.

Please align the fields name (e.g. [1]) so that it's easier to 
distinguish between fields type and name.

Let's also prefix with "ne" the data structure naming e.g. 
ne_phys_contig_mem_regions. So that is similar to other data structures 
defined in the NE kernel driver codebase.

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/virt/nitro_enclaves/ne_misc_dev.c#n118

> +};
> +
> +/**
>    * ne_check_enclaves_created() - Verify if at least one enclave has been created.
>    * @void:      No parameters provided.
>    *
> @@ -825,6 +836,33 @@ static int ne_sanity_check_user_mem_region_page(struct ne_enclave *ne_enclave,
>   }
>
>   /**
> + * ne_merge_phys_contig_memory_regions() - Add a memory region and merge the adjacent
> + *                                         regions if they are physical contiguous.

physical contiguous => physically contiguous

> + * @regions   : Private data associated with the physical contiguous memory regions.

physical contiguous memory regions => contiguous physical memory regions

@regions => @phys_contig_regions

> + * @page_paddr: Physical start address of the region to be added.
> + * @page_size : Length of the region to be added.
> + *
> + * Return:
> + * * No return value.

Please add "Context: Process context. This function is called with the 
ne_enclave mutex held." before "Return", similar to other defined functions.

Can remove these lines, as for now there is no return value:

* Return:
* * No return value.

And then can add this in the second patch in the series:

* Context: Process context. This function is called with the ne_enclave 
mutex held. (note: already available in the first patch)
* Return: (note: added in the second patch)
* * 0 ...

> + */
> +static void
> +ne_merge_phys_contig_memory_regions(struct phys_contig_mem_regions *regions,
> +                                   u64 page_paddr, u64 page_size)

phys_contig_mem_regions => ne_phys_contig_mem_regions
*regions => *phys_contig_regions

Can define something like this:

unsigned long num = phys_contig_regions->num;

and then use it inside the function, except the last line that 
increments the num.

> +{
> +       /* Physical contiguous, just merge */

Physical contiguous => Physically contiguous

> +       if (regions->num &&
> +           (regions->region[regions->num - 1].end + 1) == page_paddr) {

e.g. phys_contig_regions->regions[num - 1]

> +               regions->region[regions->num - 1].end += page_size;
> +
> +               return;
> +       }
> +
> +       regions->region[regions->num].start = page_paddr;
> +       regions->region[regions->num].end = page_paddr + page_size - 1;
> +       regions->num++;
> +}
> +
> +/**
>    * ne_set_user_memory_region_ioctl() - Add user space memory region to the slot
>    *                                    associated with the current enclave.
>    * @ne_enclave :       Private data associated with the current enclave.
> @@ -843,9 +881,9 @@ static int ne_set_user_memory_region_ioctl(struct ne_enclave *ne_enclave,
>          unsigned long max_nr_pages = 0;
>          unsigned long memory_size = 0;
>          struct ne_mem_region *ne_mem_region = NULL;
> -       unsigned long nr_phys_contig_mem_regions = 0;
>          struct pci_dev *pdev = ne_devs.ne_pci_dev->pdev;
> -       struct page **phys_contig_mem_regions = NULL;
> +       struct phys_contig_mem_regions *phys_contig_mem_regions = NULL;

struct phys_contig_mem_regions *phys_contig_mem_regions = NULL; => 
struct ne_phys_contig_mem_regions phys_contig_mem_regions = {};

> +       size_t size_to_alloc = 0;
>          int rc = -EINVAL;
>
>          rc = ne_sanity_check_user_mem_region(ne_enclave, mem_region);
> @@ -866,8 +904,9 @@ static int ne_set_user_memory_region_ioctl(struct ne_enclave *ne_enclave,
>                  goto free_mem_region;
>          }
>
> -       phys_contig_mem_regions = kcalloc(max_nr_pages, sizeof(*phys_contig_mem_regions),
> -                                         GFP_KERNEL);
> +       size_to_alloc = sizeof(*phys_contig_mem_regions) +
> +                       max_nr_pages * sizeof(struct range);
> +       phys_contig_mem_regions = kzalloc(size_to_alloc, GFP_KERNEL);

Then can alloc memory for the regions field.

phys_contig_mem_regions.regions = kcalloc(max_nr_pages, 
sizeof(*phys_contig_mem_regions.regions), GFP_KERNEL);

The "size_of_alloc" will not be needed in this case.

>          if (!phys_contig_mem_regions) {
>                  rc = -ENOMEM;
>
> @@ -901,26 +940,16 @@ static int ne_set_user_memory_region_ioctl(struct ne_enclave *ne_enclave,
>                  if (rc < 0)
>                          goto put_pages;
>
> -               /*
> -                * TODO: Update once handled non-contiguous memory regions
> -                * received from user space or contiguous physical memory regions
> -                * larger than 2 MiB e.g. 8 MiB.
> -                */
> -               phys_contig_mem_regions[i] = ne_mem_region->pages[i];
> +               ne_merge_phys_contig_memory_regions(phys_contig_mem_regions,

And can pass it here like this: &phys_contig_mem_regions.

> +                                                   page_to_phys(ne_mem_region->pages[i]),
> +                                                   page_size(ne_mem_region->pages[i]));
>
>                  memory_size += page_size(ne_mem_region->pages[i]);
>
>                  ne_mem_region->nr_pages++;
>          } while (memory_size < mem_region.memory_size);
>
> -       /*
> -        * TODO: Update once handled non-contiguous memory regions received
> -        * from user space or contiguous physical memory regions larger than
> -        * 2 MiB e.g. 8 MiB.
> -        */
> -       nr_phys_contig_mem_regions = ne_mem_region->nr_pages;
> -
> -       if ((ne_enclave->nr_mem_regions + nr_phys_contig_mem_regions) >
> +       if ((ne_enclave->nr_mem_regions + phys_contig_mem_regions->num) >
>              ne_enclave->max_mem_regions) {
>                  dev_err_ratelimited(ne_misc_dev.this_device,
>                                      "Reached max memory regions %lld\n",
> @@ -931,9 +960,10 @@ static int ne_set_user_memory_region_ioctl(struct ne_enclave *ne_enclave,
>                  goto put_pages;
>          }
>
> -       for (i = 0; i < nr_phys_contig_mem_regions; i++) {
> -               u64 phys_region_addr = page_to_phys(phys_contig_mem_regions[i]);
> -               u64 phys_region_size = page_size(phys_contig_mem_regions[i]);
> +       for (i = 0; i < phys_contig_mem_regions->num; i++) {
> +               struct range *range = phys_contig_mem_regions->region + i;
> +               u64 phys_region_addr = range->start;
> +               u64 phys_region_size = range_len(range);

With the updated data structure field, could be:

u64 phys_region_addr = phys_contig_mem_regions.regions[i].start;
u64 phys_region_size = range_len(&phys_contig_mem_regions.regions[i]);

>                  if (phys_region_size & (NE_MIN_MEM_REGION_SIZE - 1)) {
>                          dev_err_ratelimited(ne_misc_dev.this_device,
> @@ -959,13 +989,14 @@ static int ne_set_user_memory_region_ioctl(struct ne_enclave *ne_enclave,
>
>          list_add(&ne_mem_region->mem_region_list_entry, &ne_enclave->mem_regions_list);
>
> -       for (i = 0; i < nr_phys_contig_mem_regions; i++) {
> +       for (i = 0; i < phys_contig_mem_regions->num; i++) {
>                  struct ne_pci_dev_cmd_reply cmd_reply = {};
>                  struct slot_add_mem_req slot_add_mem_req = {};
> +               struct range *range = phys_contig_mem_regions->region + i;
>
>                  slot_add_mem_req.slot_uid = ne_enclave->slot_uid;
> -               slot_add_mem_req.paddr = page_to_phys(phys_contig_mem_regions[i]);
> -               slot_add_mem_req.size = page_size(phys_contig_mem_regions[i]);
> +               slot_add_mem_req.paddr = range->start;
> +               slot_add_mem_req.size = range_len(range);

Similarly here:

slot_add_mem_req.paddr = phys_contig_mem_regions.regions[i].start;
slot_add_mem_req.size = range_len(&phys_contig_mem_regions.regions[i]);

Then remain the kfree paths for "phys_contig_mem_regions.regions" 
instead of "phys_contig_mem_regions".

Thanks,
Andra

>                  rc = ne_do_request(pdev, SLOT_ADD_MEM,
>                                     &slot_add_mem_req, sizeof(slot_add_mem_req),
> --
> 1.8.3.1



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