From eeba74747a6634c59887750efcf534b335899993 Mon Sep 17 00:00:00 2001 From: Li Ming Date: Fri, 21 Feb 2025 09:24:47 +0800 Subject: [PATCH 1/7] cxl/core: Use guard() to replace open-coded down_read/write() Some down/up_read() and down/up_write() cases can be replaced by a guard() simply to drop explicit unlock invoked. It helps to align coding style with current CXL subsystem's. Reviewed-by: Jonathan Cameron Reviewed-by: Dave Jiang Reviewed-by: Alison Schofield Reviewed-by: Ira Weiny Acked-by: Davidlohr Bueso Signed-off-by: Li Ming Link: https://patch.msgid.link/20250221012453.126366-2-ming.li@zohomail.com Signed-off-by: Dave Jiang --- drivers/cxl/core/hdm.c | 15 +++++---------- drivers/cxl/core/memdev.c | 9 +++------ drivers/cxl/core/port.c | 8 ++------ drivers/cxl/core/region.c | 8 +++----- 4 files changed, 13 insertions(+), 27 deletions(-) diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c index 50e6a45b30ba..4a578092377e 100644 --- a/drivers/cxl/core/hdm.c +++ b/drivers/cxl/core/hdm.c @@ -213,13 +213,12 @@ void cxl_dpa_debug(struct seq_file *file, struct cxl_dev_state *cxlds) { struct resource *p1, *p2; - down_read(&cxl_dpa_rwsem); + guard(rwsem_read)(&cxl_dpa_rwsem); for (p1 = cxlds->dpa_res.child; p1; p1 = p1->sibling) { __cxl_dpa_debug(file, p1, 0); for (p2 = p1->child; p2; p2 = p2->sibling) __cxl_dpa_debug(file, p2, 1); } - up_read(&cxl_dpa_rwsem); } EXPORT_SYMBOL_NS_GPL(cxl_dpa_debug, "CXL"); @@ -250,9 +249,8 @@ static void __cxl_dpa_release(struct cxl_endpoint_decoder *cxled) static void cxl_dpa_release(void *cxled) { - down_write(&cxl_dpa_rwsem); + guard(rwsem_write)(&cxl_dpa_rwsem); __cxl_dpa_release(cxled); - up_write(&cxl_dpa_rwsem); } /* @@ -362,14 +360,11 @@ EXPORT_SYMBOL_NS_GPL(devm_cxl_dpa_reserve, "CXL"); resource_size_t cxl_dpa_size(struct cxl_endpoint_decoder *cxled) { - resource_size_t size = 0; - - down_read(&cxl_dpa_rwsem); + guard(rwsem_read)(&cxl_dpa_rwsem); if (cxled->dpa_res) - size = resource_size(cxled->dpa_res); - up_read(&cxl_dpa_rwsem); + return resource_size(cxled->dpa_res); - return size; + return 0; } resource_size_t cxl_dpa_resource_start(struct cxl_endpoint_decoder *cxled) diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c index ae3dfcbe8938..98c05426aa4a 100644 --- a/drivers/cxl/core/memdev.c +++ b/drivers/cxl/core/memdev.c @@ -564,10 +564,9 @@ EXPORT_SYMBOL_NS_GPL(is_cxl_memdev, "CXL"); void set_exclusive_cxl_commands(struct cxl_memdev_state *mds, unsigned long *cmds) { - down_write(&cxl_memdev_rwsem); + guard(rwsem_write)(&cxl_memdev_rwsem); bitmap_or(mds->exclusive_cmds, mds->exclusive_cmds, cmds, CXL_MEM_COMMAND_ID_MAX); - up_write(&cxl_memdev_rwsem); } EXPORT_SYMBOL_NS_GPL(set_exclusive_cxl_commands, "CXL"); @@ -579,10 +578,9 @@ EXPORT_SYMBOL_NS_GPL(set_exclusive_cxl_commands, "CXL"); void clear_exclusive_cxl_commands(struct cxl_memdev_state *mds, unsigned long *cmds) { - down_write(&cxl_memdev_rwsem); + guard(rwsem_write)(&cxl_memdev_rwsem); bitmap_andnot(mds->exclusive_cmds, mds->exclusive_cmds, cmds, CXL_MEM_COMMAND_ID_MAX); - up_write(&cxl_memdev_rwsem); } EXPORT_SYMBOL_NS_GPL(clear_exclusive_cxl_commands, "CXL"); @@ -590,9 +588,8 @@ static void cxl_memdev_shutdown(struct device *dev) { struct cxl_memdev *cxlmd = to_cxl_memdev(dev); - down_write(&cxl_memdev_rwsem); + guard(rwsem_write)(&cxl_memdev_rwsem); cxlmd->cxlds = NULL; - up_write(&cxl_memdev_rwsem); } static void cxl_memdev_unregister(void *_cxlmd) diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c index 78a5c2c25982..2c59d65bc18b 100644 --- a/drivers/cxl/core/port.c +++ b/drivers/cxl/core/port.c @@ -549,13 +549,9 @@ static ssize_t decoders_committed_show(struct device *dev, struct device_attribute *attr, char *buf) { struct cxl_port *port = to_cxl_port(dev); - int rc; - down_read(&cxl_region_rwsem); - rc = sysfs_emit(buf, "%d\n", cxl_num_decoders_committed(port)); - up_read(&cxl_region_rwsem); - - return rc; + guard(rwsem_read)(&cxl_region_rwsem); + return sysfs_emit(buf, "%d\n", cxl_num_decoders_committed(port)); } static DEVICE_ATTR_RO(decoders_committed); diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c index e8d11a988fd9..d8a71f9f9fa5 100644 --- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -3208,7 +3208,6 @@ static int match_region_by_range(struct device *dev, const void *data) struct cxl_region_params *p; struct cxl_region *cxlr; const struct range *r = data; - int rc = 0; if (!is_cxl_region(dev)) return 0; @@ -3216,12 +3215,11 @@ static int match_region_by_range(struct device *dev, const void *data) cxlr = to_cxl_region(dev); p = &cxlr->params; - down_read(&cxl_region_rwsem); + guard(rwsem_read)(&cxl_region_rwsem); if (p->res && p->res->start == r->start && p->res->end == r->end) - rc = 1; - up_read(&cxl_region_rwsem); + return 1; - return rc; + return 0; } /* Establish an empty region covering the given HPA range */ From 3ad4f59f38965071e429ace93c75a94a2ede5456 Mon Sep 17 00:00:00 2001 From: Li Ming Date: Fri, 21 Feb 2025 09:24:48 +0800 Subject: [PATCH 2/7] cxl/core: cxl_mem_sanitize() cleanup In cxl_mem_sanitize(), the down_read() and up_read() for cxl_region_rwsem can be simply replaced by a guard(rwsem_read), and the local variable 'rc' can be removed. Reviewed-by: Jonathan Cameron Reviewed-by: Dave Jiang Reviewed-by: Alison Schofield Reviewed-by: Ira Weiny Acked-by: Davidlohr Bueso Signed-off-by: Li Ming Link: https://patch.msgid.link/20250221012453.126366-3-ming.li@zohomail.com Signed-off-by: Dave Jiang --- drivers/cxl/core/mbox.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c index 548564c770c0..0601297af0c9 100644 --- a/drivers/cxl/core/mbox.c +++ b/drivers/cxl/core/mbox.c @@ -1222,23 +1222,19 @@ int cxl_mem_sanitize(struct cxl_memdev *cxlmd, u16 cmd) { struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlmd->cxlds); struct cxl_port *endpoint; - int rc; /* synchronize with cxl_mem_probe() and decoder write operations */ guard(device)(&cxlmd->dev); endpoint = cxlmd->endpoint; - down_read(&cxl_region_rwsem); + guard(rwsem_read)(&cxl_region_rwsem); /* * Require an endpoint to be safe otherwise the driver can not * be sure that the device is unmapped. */ if (endpoint && cxl_num_decoders_committed(endpoint) == 0) - rc = __cxl_mem_sanitize(mds, cmd); - else - rc = -EBUSY; - up_read(&cxl_region_rwsem); + return __cxl_mem_sanitize(mds, cmd); - return rc; + return -EBUSY; } static int add_dpa_res(struct device *dev, struct resource *parent, From a58afda8bfd4a113295f0e12c0697c35a69614b2 Mon Sep 17 00:00:00 2001 From: Li Ming Date: Fri, 21 Feb 2025 09:24:49 +0800 Subject: [PATCH 3/7] cxl/memdev: cxl_memdev_ioctl() cleanup In cxl_memdev_ioctl(), the down_read(&cxl_memdev_rwsem) and up_read(&cxl_memdev_rwsem) can be replaced by a guard(rwsem_read)(&cxl_memdev_rwsem), it helps to remove the open-coded up_read(&cxl_memdev_rwsem). Besides, the local var 'rc' can be also removed to make the code more cleaner. Reviewed-by: Jonathan Cameron Reviewed-by: Dave Jiang Reviewed-by: Alison Schofield Reviewed-by: Ira Weiny Acked-by: Davidlohr Bueso Signed-off-by: Li Ming Link: https://patch.msgid.link/20250221012453.126366-4-ming.li@zohomail.com Signed-off-by: Dave Jiang --- drivers/cxl/core/memdev.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c index 98c05426aa4a..6f90dcd626f9 100644 --- a/drivers/cxl/core/memdev.c +++ b/drivers/cxl/core/memdev.c @@ -668,15 +668,13 @@ static long cxl_memdev_ioctl(struct file *file, unsigned int cmd, { struct cxl_memdev *cxlmd = file->private_data; struct cxl_dev_state *cxlds; - int rc = -ENXIO; - down_read(&cxl_memdev_rwsem); + guard(rwsem_read)(&cxl_memdev_rwsem); cxlds = cxlmd->cxlds; if (cxlds && cxlds->type == CXL_DEVTYPE_CLASSMEM) - rc = __cxl_memdev_ioctl(cxlmd, cmd, arg); - up_read(&cxl_memdev_rwsem); + return __cxl_memdev_ioctl(cxlmd, cmd, arg); - return rc; + return -ENXIO; } static int cxl_memdev_open(struct inode *inode, struct file *file) From 16fe6ec4ac3d828b3976bd36e4d99af73f8e43d2 Mon Sep 17 00:00:00 2001 From: Li Ming Date: Fri, 21 Feb 2025 09:24:50 +0800 Subject: [PATCH 4/7] cxl/core: Use guard() to drop the goto pattern of cxl_dpa_free() cxl_dpa_free() has a goto pattern to call up_write() for cxl_dpa_rwsem, it can be removed by using a guard() to replace the down_write() and up_write(). Reviewed-by: Jonathan Cameron Reviewed-by: Dave Jiang Reviewed-by: Alison Schofield Reviewed-by: Ira Weiny Acked-by: Davidlohr Bueso Signed-off-by: Li Ming Link: https://patch.msgid.link/20250221012453.126366-5-ming.li@zohomail.com Signed-off-by: Dave Jiang --- drivers/cxl/core/hdm.c | 24 ++++++++---------------- 1 file changed, 8 insertions(+), 16 deletions(-) diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c index 4a578092377e..874a791f8292 100644 --- a/drivers/cxl/core/hdm.c +++ b/drivers/cxl/core/hdm.c @@ -382,35 +382,27 @@ int cxl_dpa_free(struct cxl_endpoint_decoder *cxled) { struct cxl_port *port = cxled_to_port(cxled); struct device *dev = &cxled->cxld.dev; - int rc; - down_write(&cxl_dpa_rwsem); - if (!cxled->dpa_res) { - rc = 0; - goto out; - } + guard(rwsem_write)(&cxl_dpa_rwsem); + if (!cxled->dpa_res) + return 0; if (cxled->cxld.region) { dev_dbg(dev, "decoder assigned to: %s\n", dev_name(&cxled->cxld.region->dev)); - rc = -EBUSY; - goto out; + return -EBUSY; } if (cxled->cxld.flags & CXL_DECODER_F_ENABLE) { dev_dbg(dev, "decoder enabled\n"); - rc = -EBUSY; - goto out; + return -EBUSY; } if (cxled->cxld.id != port->hdm_end) { dev_dbg(dev, "expected decoder%d.%d\n", port->id, port->hdm_end); - rc = -EBUSY; - goto out; + return -EBUSY; } + devm_cxl_dpa_release(cxled); - rc = 0; -out: - up_write(&cxl_dpa_rwsem); - return rc; + return 0; } int cxl_dpa_set_mode(struct cxl_endpoint_decoder *cxled, From a81ebe7d19b6fdc6de0159878fbed9945120813e Mon Sep 17 00:00:00 2001 From: Li Ming Date: Fri, 21 Feb 2025 09:24:51 +0800 Subject: [PATCH 5/7] cxl/core: Use guard() to drop goto pattern of cxl_dpa_alloc() In cxl_dpa_alloc(), some checking and operations need to be protected by a rwsem called cxl_dpa_rwsem, so there is a goto pattern in cxl_dpa_alloc() to release the rwsem. The goto pattern can be optimized by using guard() to hold the rwsem. Creating a new function called __cxl_dpa_alloc() to include all checking and operations needed to be protected by cxl_dpa_rwsem. Using guard(rwsem_write()) to hold cxl_dpa_rwsem at the beginning of the new function. Reviewed-by: Jonathan Cameron Reviewed-by: Dave Jiang Reviewed-by: Alison Schofield Reviewed-by: Dan Williams Reviewed-by: Ira Weiny Acked-by: Davidlohr Bueso Signed-off-by: Li Ming Link: https://patch.msgid.link/20250221012453.126366-6-ming.li@zohomail.com Signed-off-by: Dave Jiang --- drivers/cxl/core/hdm.c | 29 ++++++++++++++--------------- 1 file changed, 14 insertions(+), 15 deletions(-) diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c index 874a791f8292..1edbf7873471 100644 --- a/drivers/cxl/core/hdm.c +++ b/drivers/cxl/core/hdm.c @@ -442,29 +442,25 @@ int cxl_dpa_set_mode(struct cxl_endpoint_decoder *cxled, return 0; } -int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size) +static int __cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size) { struct cxl_memdev *cxlmd = cxled_to_memdev(cxled); resource_size_t free_ram_start, free_pmem_start; - struct cxl_port *port = cxled_to_port(cxled); struct cxl_dev_state *cxlds = cxlmd->cxlds; struct device *dev = &cxled->cxld.dev; resource_size_t start, avail, skip; struct resource *p, *last; - int rc; - down_write(&cxl_dpa_rwsem); + guard(rwsem_write)(&cxl_dpa_rwsem); if (cxled->cxld.region) { dev_dbg(dev, "decoder attached to %s\n", dev_name(&cxled->cxld.region->dev)); - rc = -EBUSY; - goto out; + return -EBUSY; } if (cxled->cxld.flags & CXL_DECODER_F_ENABLE) { dev_dbg(dev, "decoder enabled\n"); - rc = -EBUSY; - goto out; + return -EBUSY; } for (p = cxlds->ram_res.child, last = NULL; p; p = p->sibling) @@ -504,21 +500,24 @@ int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size) skip = skip_end - skip_start + 1; } else { dev_dbg(dev, "mode not set\n"); - rc = -EINVAL; - goto out; + return -EINVAL; } if (size > avail) { dev_dbg(dev, "%pa exceeds available %s capacity: %pa\n", &size, cxl_decoder_mode_name(cxled->mode), &avail); - rc = -ENOSPC; - goto out; + return -ENOSPC; } - rc = __cxl_dpa_reserve(cxled, start, size, skip); -out: - up_write(&cxl_dpa_rwsem); + return __cxl_dpa_reserve(cxled, start, size, skip); +} +int cxl_dpa_alloc(struct cxl_endpoint_decoder *cxled, unsigned long long size) +{ + struct cxl_port *port = cxled_to_port(cxled); + int rc; + + rc = __cxl_dpa_alloc(cxled, size); if (rc) return rc; From 9e7b7ab5af69aaa5cd027656529663407da61e6f Mon Sep 17 00:00:00 2001 From: Li Ming Date: Fri, 21 Feb 2025 09:24:52 +0800 Subject: [PATCH 6/7] cxl/region: Drop goto pattern in cxl_dax_region_alloc() In cxl_dax_region_alloc(), there is a goto pattern to release the rwsem cxl_region_rwsem when the function returns, the down_read() and up_read can be replaced by a guard(rwsem_read) then the goto pattern can be removed. Reviewed-by: Jonathan Cameron Reviewed-by: Dave Jiang Reviewed-by: Alison Schofield Reviewed-by: Ira Weiny Acked-by: Davidlohr Bueso Signed-off-by: Li Ming Link: https://patch.msgid.link/20250221012453.126366-7-ming.li@zohomail.com Signed-off-by: Dave Jiang --- drivers/cxl/core/region.c | 16 +++++----------- 1 file changed, 5 insertions(+), 11 deletions(-) diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c index d8a71f9f9fa5..320a3f218131 100644 --- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -3038,17 +3038,13 @@ static struct cxl_dax_region *cxl_dax_region_alloc(struct cxl_region *cxlr) struct cxl_dax_region *cxlr_dax; struct device *dev; - down_read(&cxl_region_rwsem); - if (p->state != CXL_CONFIG_COMMIT) { - cxlr_dax = ERR_PTR(-ENXIO); - goto out; - } + guard(rwsem_read)(&cxl_region_rwsem); + if (p->state != CXL_CONFIG_COMMIT) + return ERR_PTR(-ENXIO); cxlr_dax = kzalloc(sizeof(*cxlr_dax), GFP_KERNEL); - if (!cxlr_dax) { - cxlr_dax = ERR_PTR(-ENOMEM); - goto out; - } + if (!cxlr_dax) + return ERR_PTR(-ENOMEM); cxlr_dax->hpa_range.start = p->res->start; cxlr_dax->hpa_range.end = p->res->end; @@ -3061,8 +3057,6 @@ static struct cxl_dax_region *cxl_dax_region_alloc(struct cxl_region *cxlr) dev->parent = &cxlr->dev; dev->bus = &cxl_bus_type; dev->type = &cxl_dax_region_type; -out: - up_read(&cxl_region_rwsem); return cxlr_dax; } From 5ec67596e368cdddddd6770fc2dd2e577e82fbe8 Mon Sep 17 00:00:00 2001 From: Li Ming Date: Fri, 21 Feb 2025 09:32:05 +0800 Subject: [PATCH 7/7] cxl/region: Drop goto pattern of construct_region() Some operations need to be protected by the cxl_region_rwsem in construct_region(). Currently, construct_region() uses down_write() and up_write() for the cxl_region_rwsem locking, so there is a goto pattern after down_write() invoked to release cxl_region_rwsem. construct region() can be optimized to remove the goto pattern. The changes are creating a new function called __construct_region() which will include all checking and operations protected by the cxl_region_rwsem, and using guard(rwsem_write) to replace down_write() and up_write() in __construct_region(). Reviewed-by: Jonathan Cameron Reviewed-by: Dave Jiang Reviewed-by: Alison Schofield Reviewed-by: Dan Williams Reviewed-by: Ira Weiny Acked-by: Davidlohr Bueso Signed-off-by: Li Ming Link: https://patch.msgid.link/20250221013205.126419-1-ming.li@zohomail.com Signed-off-by: Dave Jiang --- drivers/cxl/core/region.c | 71 +++++++++++++++++++++------------------ 1 file changed, 39 insertions(+), 32 deletions(-) diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c index 320a3f218131..a750107a3bff 100644 --- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -3216,49 +3216,31 @@ static int match_region_by_range(struct device *dev, const void *data) return 0; } -/* Establish an empty region covering the given HPA range */ -static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd, - struct cxl_endpoint_decoder *cxled) +static int __construct_region(struct cxl_region *cxlr, + struct cxl_root_decoder *cxlrd, + struct cxl_endpoint_decoder *cxled) { struct cxl_memdev *cxlmd = cxled_to_memdev(cxled); - struct cxl_port *port = cxlrd_to_port(cxlrd); struct range *hpa = &cxled->cxld.hpa_range; struct cxl_region_params *p; - struct cxl_region *cxlr; struct resource *res; int rc; - do { - cxlr = __create_region(cxlrd, cxled->mode, - atomic_read(&cxlrd->region_id)); - } while (IS_ERR(cxlr) && PTR_ERR(cxlr) == -EBUSY); - - if (IS_ERR(cxlr)) { - dev_err(cxlmd->dev.parent, - "%s:%s: %s failed assign region: %ld\n", - dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev), - __func__, PTR_ERR(cxlr)); - return cxlr; - } - - down_write(&cxl_region_rwsem); + guard(rwsem_write)(&cxl_region_rwsem); p = &cxlr->params; if (p->state >= CXL_CONFIG_INTERLEAVE_ACTIVE) { dev_err(cxlmd->dev.parent, "%s:%s: %s autodiscovery interrupted\n", dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev), __func__); - rc = -EBUSY; - goto err; + return -EBUSY; } set_bit(CXL_REGION_F_AUTO, &cxlr->flags); res = kmalloc(sizeof(*res), GFP_KERNEL); - if (!res) { - rc = -ENOMEM; - goto err; - } + if (!res) + return -ENOMEM; *res = DEFINE_RES_MEM_NAMED(hpa->start, range_len(hpa), dev_name(&cxlr->dev)); @@ -3281,7 +3263,7 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd, rc = sysfs_update_group(&cxlr->dev.kobj, get_cxl_region_target_group()); if (rc) - goto err; + return rc; dev_dbg(cxlmd->dev.parent, "%s:%s: %s %s res: %pr iw: %d ig: %d\n", dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev), __func__, @@ -3290,14 +3272,39 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd, /* ...to match put_device() in cxl_add_to_region() */ get_device(&cxlr->dev); - up_write(&cxl_region_rwsem); + + return 0; +} + +/* Establish an empty region covering the given HPA range */ +static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd, + struct cxl_endpoint_decoder *cxled) +{ + struct cxl_memdev *cxlmd = cxled_to_memdev(cxled); + struct cxl_port *port = cxlrd_to_port(cxlrd); + struct cxl_region *cxlr; + int rc; + + do { + cxlr = __create_region(cxlrd, cxled->mode, + atomic_read(&cxlrd->region_id)); + } while (IS_ERR(cxlr) && PTR_ERR(cxlr) == -EBUSY); + + if (IS_ERR(cxlr)) { + dev_err(cxlmd->dev.parent, + "%s:%s: %s failed assign region: %ld\n", + dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev), + __func__, PTR_ERR(cxlr)); + return cxlr; + } + + rc = __construct_region(cxlr, cxlrd, cxled); + if (rc) { + devm_release_action(port->uport_dev, unregister_region, cxlr); + return ERR_PTR(rc); + } return cxlr; - -err: - up_write(&cxl_region_rwsem); - devm_release_action(port->uport_dev, unregister_region, cxlr); - return ERR_PTR(rc); } int cxl_add_to_region(struct cxl_port *root, struct cxl_endpoint_decoder *cxled)