On Tue, Mar 8, 2016 at 12:05 PM, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Tue, Mar 8, 2016 at 10:08 AM, Toshi Kani <toshi.kani@xxxxxxx> wrote: >> >> Add device-managed implementaions of insert_resource() and >> remove_resouce() functions. > > Can we get an example of the users and show how much this would actually help? > > insert_resource() is fairly unusual to begin with, and it should > basically *never* be used by a driver at all (it's more of a bus > thing). > > The patch doesn't look _wrong_, but it does look potentially largely > pointless. Adding new interfaces to do things that aren't common > enough to worry about is counter-productive, imho. Here's the usage patch from Toshi [1] (copied below). It is indeed a resource injected by nfit / nvdimm bus implementation. We just happen to support nfit and libnvdimm as modules. The goal of these patches is to use the ACPI NFIT data to create a "Persistent Memory" rather than "reserved" resource. This is for platform-firmware implementations that use E820-Type2 rather than E820-Type7 to describe pmem. [1]: https://patchwork.kernel.org/patch/8485691/ 8<-- From: Toshi Kani <toshi.kani@xxxxxxx> ACPI 6.0 defines persistent memory (PMEM) ranges in multiple firmware interfaces, e820, EFI, and ACPI NFIT table. This EFI change, however, leads to hit a bug in the grub bootloader, which treats EFI_PERSISTENT_MEMORY type as regular memory and corrupts stored user data [1]. Therefore, BIOS may set generic reserved type in e820 and EFI to cover PMEM ranges. The kernel can initialize PMEM ranges from ACPI NFIT table alone. This scheme causes a problem in the iomem table, though. On x86, for instance, e820_reserve_resources() initializes top-level entries (iomem_resource.child) from the e820 table at early boot-time. This creates "reserved" entry for a PMEM range, which does not allow region_intersects() to check with PMEM type. Change acpi_nfit_register_region() to call acpi_nfit_insert_resource(), which calls devm_insert_resource() to insert a PMEM entry from NFIT when the iomem table does not have a PMEM entry already. That is, when a PMEM range is marked as reserved type in e820, it inserts "Persistent Memory" entry, which results as follows. + "Persistent Memory" + "reserved" This allows the EINJ driver, which calls region_intersects() to check PMEM ranges, to work continuously even if BIOS sets reserved type (or sets nothing) to PMEM ranges in e820 and EFI. [1]: https://lists.gnu.org/archive/html/grub-devel/2015-11/msg00209.html Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx> Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/acpi/nfit.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c index fb53db1..d97b53f 100644 --- a/drivers/acpi/nfit.c +++ b/drivers/acpi/nfit.c @@ -1571,6 +1571,30 @@ static int ars_status_process_records(struct nvdimm_bus *nvdimm_bus, return 0; } +static int acpi_nfit_insert_resource(struct acpi_nfit_desc *acpi_desc, + struct nd_region_desc *ndr_desc) +{ + struct resource *res, *nd_res = ndr_desc->res; + size_t size = nd_res->end - nd_res->start + 1; + + /* No operation if the region is already registered as PMEM */ + if (region_intersects(nd_res->start, size, IORESOURCE_MEM, + IORES_DESC_PERSISTENT_MEMORY) == REGION_INTERSECTS) + return 0; + + res = devm_kzalloc(acpi_desc->dev, sizeof(*res), GFP_KERNEL); + if (!res) + return -ENOMEM; + + res->name = "Persistent Memory"; + res->start = nd_res->start; + res->end = nd_res->end; + res->flags = IORESOURCE_MEM; + res->desc = IORES_DESC_PERSISTENT_MEMORY; + + return devm_insert_resource(acpi_desc->dev, &iomem_resource, res); +} + static int acpi_nfit_find_poison(struct acpi_nfit_desc *acpi_desc, struct nd_region_desc *ndr_desc) { @@ -1781,6 +1805,12 @@ static int acpi_nfit_register_region(struct acpi_nfit_desc *acpi_desc, nvdimm_bus = acpi_desc->nvdimm_bus; if (nfit_spa_type(spa) == NFIT_SPA_PM) { + rc = acpi_nfit_insert_resource(acpi_desc, ndr_desc); + if (rc) + dev_warn(acpi_desc->dev, + "failed to insert pmem resource to iomem: %d\n", + rc); + rc = acpi_nfit_find_poison(acpi_desc, ndr_desc); if (rc) { dev_err(acpi_desc->dev, -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
