On Thu, Jan 27, 2022 at 4:27 PM Ben Widawsky <ben.widawsky@xxxxxxxxx> wrote:
>
> When a region is not assigned a host physical address,
Curious, is there a way to pick one in the current ABI? Not that I
want one, in fact I think Linux should make it as difficult as
possible to create a region with a fixed address (per the 'HPA' field
of the region label) given all the problems it can cause with decoder
allocation ordering. Unless and until someone identifies a solid use
case for that capability it should be de-emphasized.
> one is picked by
> the driver. As the address will determine which CFMWS contains the
> region, it's usually a better idea to let the driver make this
> determination.
>
> Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
> ---
> drivers/cxl/region.c | 40 ++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 38 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cxl/region.c b/drivers/cxl/region.c
> index cc41939a2f0a..5588873dd250 100644
> --- a/drivers/cxl/region.c
> +++ b/drivers/cxl/region.c
> @@ -1,6 +1,7 @@
> // SPDX-License-Identifier: GPL-2.0-only
> /* Copyright(c) 2021 Intel Corporation. All rights reserved. */
> #include <linux/platform_device.h>
> +#include <linux/genalloc.h>
> #include <linux/device.h>
> #include <linux/module.h>
> #include <linux/pci.h>
> @@ -64,6 +65,20 @@ static struct cxl_port *get_root_decoder(const struct cxl_memdev *endpoint)
> return NULL;
> }
>
> +static void release_cxl_region(void *r)
> +{
> + struct cxl_region *cxlr = (struct cxl_region *)r;
> + struct cxl_decoder *rootd = rootd_from_region(cxlr);
> + struct resource *res = &rootd->platform_res;
> + resource_size_t start, size;
> +
> + start = cxlr->res->start;
> + size = resource_size(cxlr->res);
> +
> + __release_region(res, start, size);
> + gen_pool_free(rootd->address_space, start, size);
If the need to keep the gen_pool in sync is dropped then this
open-coded devm release handler can be replaced with
__devm_request_region().
> +}
> +
> /**
> * sanitize_region() - Check is region is reasonably configured
> * @cxlr: The region to check
> @@ -129,8 +144,29 @@ static int sanitize_region(const struct cxl_region *cxlr)
> */
> static int allocate_address_space(struct cxl_region *cxlr)
> {
> - /* TODO */
The problem with TODOs is now I forget which context calls
allocate_address_space(). If the caller was added in this patch it
would be reviewable, as is, I need to go to another window to search
"allocate_address_space" to recall that it is called from
cxl_region_probe(). That's too late as someone defining a region
should know upfront a region creation time that space has been
reserved, or not.
> - return 0;
> + struct cxl_decoder *rootd = rootd_from_region(cxlr);
> + unsigned long start;
s/unsigned long/resource_size_t/?
> +
> + start = gen_pool_alloc(rootd->address_space, cxlr->config.size);
> + if (!start) {
> + dev_dbg(&cxlr->dev, "Couldn't allocate %lluM of address space",
> + cxlr->config.size >> 20);
> + return -ENOMEM;
> + }
> +
> + cxlr->res =
> + __request_region(&rootd->platform_res, start, cxlr->config.size,
> + dev_name(&cxlr->dev), IORESOURCE_MEM);
> + if (!cxlr->res) {
> + dev_dbg(&cxlr->dev, "Couldn't obtain region from %s (%pR)\n",
> + dev_name(&rootd->dev), &rootd->platform_res);
> + gen_pool_free(rootd->address_space, start, cxlr->config.size);
> + return -ENOMEM;
> + }
> +
> + dev_dbg(&cxlr->dev, "resource %pR", cxlr->res);
> +
> + return devm_add_action_or_reset(&cxlr->dev, release_cxl_region, cxlr);
> }
>
> /**
> --
> 2.35.0
>
