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device-dax: add dis-contiguous resource support

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Break the requirement that device-dax instances are physically contiguous.
With this constraint removed it allows fragmented available capacity to
be fully allocated.

This capability is useful to mitigate the "noisy neighbor" problem with
memory-side-cache management for virtual machines, or any other scenario
where a platform address boundary also designates a performance boundary.
For example a direct mapped memory side cache might rotate cache colors at
1GB boundaries.  With dis-contiguous allocations a device-dax instance
could be configured to contain only 1 cache color.

It also satisfies Joao's use case (see link) for partitioning memory for
exclusive guest access.  It allows for a future potential mode where the
host kernel need not allocate 'struct page' capacity up-front.

Reported-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brice Goglin <Brice.Goglin@inria.fr>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: David Hildenbrand <david@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Hulk Robot <hulkci@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Jason Yan <yanaijie@huawei.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Jia He <justin.he@arm.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Paul Mackerras <paulus@ozlabs.org>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/lkml/20200110190313.17144-1-joao.m.martins@oracle.com/
Link: https://lkml.kernel.org/r/159643104304.4062302.16561669534797528660.stgit@dwillia2-desk3.amr.corp.intel.com
Link: https://lkml.kernel.org/r/160106116875.30709.11456649969327399771.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dan Williams
2020-10-13 16:50:39 -07:00
committed by Linus Torvalds
parent b7b3c01b19
commit 60e93dc097
5 changed files with 320 additions and 121 deletions
Download Patch File Download Diff File Expand all files Collapse all files

126
drivers/dax/kmem.c
View File

@@ -19,24 +19,28 @@ static const char *kmem_name;
/* Set if any memory will remain added when the driver will be unloaded. */
static bool any_hotremove_failed;
static struct range dax_kmem_range(struct dev_dax *dev_dax)
static int dax_kmem_range(struct dev_dax *dev_dax, int i, struct range *r)
{
struct range range;
struct dev_dax_range *dax_range = &dev_dax->ranges[i];
struct range *range = &dax_range->range;
/* memory-block align the hotplug range */
range.start = ALIGN(dev_dax->range.start, memory_block_size_bytes());
range.end = ALIGN_DOWN(dev_dax->range.end + 1, memory_block_size_bytes()) - 1;
return range;
r->start = ALIGN(range->start, memory_block_size_bytes());
r->end = ALIGN_DOWN(range->end + 1, memory_block_size_bytes()) - 1;
if (r->start >= r->end) {
r->start = range->start;
r->end = range->end;
return -ENOSPC;
}
return 0;
}
static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
{
struct range range = dax_kmem_range(dev_dax);
struct device *dev = &dev_dax->dev;
struct resource *res;
int i, mapped = 0;
char *res_name;
int numa_node;
int rc;
/*
* Ensure good NUMA information for the persistent memory.
@@ -55,31 +59,58 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
if (!res_name)
return -ENOMEM;
/* Region is permanently reserved if hotremove fails. */
res = request_mem_region(range.start, range_len(&range), res_name);
if (!res) {
dev_warn(dev, "could not reserve region [%#llx-%#llx]\n", range.start, range.end);
kfree(res_name);
return -EBUSY;
}
for (i = 0; i < dev_dax->nr_range; i++) {
struct resource *res;
struct range range;
int rc;
/*
* Set flags appropriate for System RAM. Leave ..._BUSY clear
* so that add_memory() can add a child resource. Do not
* inherit flags from the parent since it may set new flags
* unknown to us that will break add_memory() below.
*/
res->flags = IORESOURCE_SYSTEM_RAM;
rc = dax_kmem_range(dev_dax, i, &range);
if (rc) {
dev_info(dev, "mapping%d: %#llx-%#llx too small after alignment\n",
i, range.start, range.end);
continue;
}
/*
* Ensure that future kexec'd kernels will not treat this as RAM
* automatically.
*/
rc = add_memory_driver_managed(numa_node, range.start, range_len(&range), kmem_name);
if (rc) {
release_mem_region(range.start, range_len(&range));
kfree(res_name);
return rc;
/* Region is permanently reserved if hotremove fails. */
res = request_mem_region(range.start, range_len(&range), res_name);
if (!res) {
dev_warn(dev, "mapping%d: %#llx-%#llx could not reserve region\n",
i, range.start, range.end);
/*
* Once some memory has been onlined we can't
* assume that it can be un-onlined safely.
*/
if (mapped)
continue;
kfree(res_name);
return -EBUSY;
}
/*
* Set flags appropriate for System RAM. Leave ..._BUSY clear
* so that add_memory() can add a child resource. Do not
* inherit flags from the parent since it may set new flags
* unknown to us that will break add_memory() below.
*/
res->flags = IORESOURCE_SYSTEM_RAM;
/*
* Ensure that future kexec'd kernels will not treat
* this as RAM automatically.
*/
rc = add_memory_driver_managed(numa_node, range.start,
range_len(&range), kmem_name);
if (rc) {
dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
i, range.start, range.end);
release_mem_region(range.start, range_len(&range));
if (mapped)
continue;
kfree(res_name);
return rc;
}
mapped++;
}
dev_set_drvdata(dev, res_name);
@@ -90,9 +121,8 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
#ifdef CONFIG_MEMORY_HOTREMOVE
static int dev_dax_kmem_remove(struct dev_dax *dev_dax)
{
int rc;
int i, success = 0;
struct device *dev = &dev_dax->dev;
struct range range = dax_kmem_range(dev_dax);
const char *res_name = dev_get_drvdata(dev);
/*
@@ -101,17 +131,31 @@ static int dev_dax_kmem_remove(struct dev_dax *dev_dax)
* there is no way to hotremove this memory until reboot because device
* unbind will succeed even if we return failure.
*/
rc = remove_memory(dev_dax->target_node, range.start, range_len(&range));
if (rc) {
for (i = 0; i < dev_dax->nr_range; i++) {
struct range range;
int rc;
rc = dax_kmem_range(dev_dax, i, &range);
if (rc)
continue;
rc = remove_memory(dev_dax->target_node, range.start,
range_len(&range));
if (rc == 0) {
release_mem_region(range.start, range_len(&range));
success++;
continue;
}
any_hotremove_failed = true;
dev_err(dev, "%#llx-%#llx cannot be hotremoved until the next reboot\n",
range.start, range.end);
return rc;
dev_err(dev,
"mapping%d: %#llx-%#llx cannot be hotremoved until the next reboot\n",
i, range.start, range.end);
}
/* Release and free dax resources */
release_mem_region(range.start, range_len(&range));
kfree(res_name);
if (success >= dev_dax->nr_range) {
kfree(res_name);
dev_set_drvdata(dev, NULL);
}
return 0;
}