lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAA9_cmc9vjChKqs7P1NG9r66TGapw0cYHfcajWh_O+hk433MTg@mail.gmail.com>
Date:	Fri, 4 Mar 2016 18:23:31 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	Toshi Kani <toshi.kani@....com>
Cc:	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	linux-mm <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] libnvdimm, pmem: adjust for section collisions
 with 'System RAM'

On Fri, Mar 4, 2016 at 6:48 PM, Toshi Kani <toshi.kani@....com> wrote:
> On Thu, 2016-03-03 at 13:53 -0800, Dan Williams wrote:
>> On a platform where 'Persistent Memory' and 'System RAM' are mixed
>> within a given sparsemem section, trim the namespace and notify about the
>> sub-optimal alignment.
>>
>> Cc: Toshi Kani <toshi.kani@....com>
>> Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
>> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
>> ---
>>  drivers/nvdimm/namespace_devs.c |    7 ++
>>  drivers/nvdimm/pfn.h            |   10 ++-
>>  drivers/nvdimm/pfn_devs.c       |    5 ++
>>  drivers/nvdimm/pmem.c           |  125 ++++++++++++++++++++++++++++-----
>> ------
>>  4 files changed, 111 insertions(+), 36 deletions(-)
>>
>> diff --git a/drivers/nvdimm/namespace_devs.c
>> b/drivers/nvdimm/namespace_devs.c
>> index 8ebfcaae3f5a..463756ca2d4b 100644
>> --- a/drivers/nvdimm/namespace_devs.c
>> +++ b/drivers/nvdimm/namespace_devs.c
>> @@ -133,6 +133,7 @@ bool nd_is_uuid_unique(struct device *dev, u8 *uuid)
>>  bool pmem_should_map_pages(struct device *dev)
>>  {
>>       struct nd_region *nd_region = to_nd_region(dev->parent);
>> +     struct nd_namespace_io *nsio;
>>
>>       if (!IS_ENABLED(CONFIG_ZONE_DEVICE))
>>               return false;
>> @@ -143,6 +144,12 @@ bool pmem_should_map_pages(struct device *dev)
>>       if (is_nd_pfn(dev) || is_nd_btt(dev))
>>               return false;
>>
>> +     nsio = to_nd_namespace_io(dev);
>> +     if (region_intersects(nsio->res.start, resource_size(&nsio-
>> >res),
>> +                             IORESOURCE_SYSTEM_RAM,
>> +                             IORES_DESC_NONE) == REGION_MIXED)
>
> Should this be != REGION_DISJOINT for safe?

Acutally, it's ok.  It doesn't need to be disjoint.  The problem is
mixing an mm-zone within a given section.  If the region intersects
system-ram then devm_memremap_pages() is a no-op and we can use the
existing page allocation and linear mapping.

>
>> +             return false;
>> +
>
>  :
>
>> @@ -304,21 +311,56 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
>>       }
>>
>>       memset(pfn_sb, 0, sizeof(*pfn_sb));
>> -     npfns = (pmem->size - SZ_8K) / SZ_4K;
>> +
>> +     /*
>> +      * Check if pmem collides with 'System RAM' when section aligned
>> and
>> +      * trim it accordingly
>> +      */
>> +     nsio = to_nd_namespace_io(&ndns->dev);
>> +     start = PHYS_SECTION_ALIGN_DOWN(nsio->res.start);
>> +     size = resource_size(&nsio->res);
>> +     if (region_intersects(start, size, IORESOURCE_SYSTEM_RAM,
>> +                             IORES_DESC_NONE) == REGION_MIXED) {
>> +
>> +             start = nsio->res.start;
>> +             start_pad = PHYS_SECTION_ALIGN_UP(start) - start;
>> +     }
>> +
>> +     start = nsio->res.start;
>> +     size = PHYS_SECTION_ALIGN_UP(start + size) - start;
>> +     if (region_intersects(start, size, IORESOURCE_SYSTEM_RAM,
>> +                             IORES_DESC_NONE) == REGION_MIXED) {
>> +             size = resource_size(&nsio->res);
>> +             end_trunc = start + size - PHYS_SECTION_ALIGN_DOWN(start
>> + size);
>> +     }
>
> This check seems to assume that guest's regular memory layout does not
> change.  That is, if there is no collision at first, there won't be any
> later.  Is this a valid assumption?

If platform firmware changes the physical alignment during the
lifetime of the namespace there's not much we can do.  Another problem
not addressed by this patch is firmware choosing to hot plug system
ram into the same section as persistent memory.  As far as I can see
all we do is ask firmware implementations to respect Linux section
boundaries and otherwise not change alignments.

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ