Linux-HyperV Archive on lore.kernel.org
 help / color / Atom feed
From: Dan Williams <dan.j.williams@intel.com>
To: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux MM <linux-mm@kvack.org>,
	virtio-dev@lists.oasis-open.org,
	virtualization@lists.linux-foundation.org,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	Linux ACPI <linux-acpi@vger.kernel.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>,
	linux-hyperv@vger.kernel.org,
	linux-s390 <linux-s390@vger.kernel.org>,
	xen-devel <xen-devel@lists.xenproject.org>,
	Michal Hocko <mhocko@kernel.org>,
	"Michael S . Tsirkin" <mst@redhat.com>,
	Michal Hocko <mhocko@suse.com>,
	Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
	Wei Yang <richard.weiyang@gmail.com>, Baoquan He <bhe@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>
Subject: Re: [PATCH v2 2/3] mm/memory_hotplug: Introduce MHP_NO_FIRMWARE_MEMMAP
Date: Sat, 2 May 2020 11:03:01 -0700
Message-ID: <CAPcyv4iqwh6k40DUy-Pwi2h5pJm9vu7+JU1ghELy=3MGM1naNg@mail.gmail.com> (raw)
In-Reply-To: <467ccba3-80ac-085c-3127-d5618d77d3e0@redhat.com>

On Sat, May 2, 2020 at 2:27 AM David Hildenbrand <david@redhat.com> wrote:
>
> >> Now, let's clarify what I want regarding virtio-mem:
> >>
> >> 1. kexec should not add virtio-mem memory to the initial firmware
> >>    memmap. The driver has to be in charge as discussed.
> >> 2. kexec should not place kexec images onto virtio-mem memory. That
> >>    would end badly.
> >> 3. kexec should still dump virtio-mem memory via kdump.
> >
> > Ok, but then seems to say to me that dax/kmem is a different type of
> > (driver managed) than virtio-mem and it's confusing to try to apply
> > the same meaning. Why not just call your type for the distinct type it
> > is "System RAM (virtio-mem)" and let any other driver managed memory
> > follow the same "System RAM ($driver)" format if it wants?
>
> I had the same idea but discarded it because it seemed to uglify the
> add_memory() interface (passing yet another parameter only relevant for
> driver managed memory). Maybe we really want a new one, because I like
> that idea:
>
> /*
>  * Add special, driver-managed memory to the system as system ram.
>  * The resource_name is expected to have the name format "System RAM
>  * ($DRIVER)", so user space (esp. kexec-tools)" can special-case it.
>  *
>  * For this memory, no entries in /sys/firmware/memmap are created,
>  * as this memory won't be part of the raw firmware-provided memory map
>  * e.g., after a reboot. Also, the created memory resource is flagged
>  * with IORESOURCE_MEM_DRIVER_MANAGED, so in-kernel users can special-
>  * case this memory (e.g., not place kexec images onto it).
>  */
> int add_memory_driver_managed(int nid, u64 start, u64 size,
>                               const char *resource_name);
>
>
> If we'd ever have to special case it even more in the kernel, we could
> allow to specify further resource flags. While passing the driver name
> instead of the resource_name would be an option, this way we don't have
> to hand craft new resource strings for added memory resources.
>
> Thoughts?

Looks useful to me and simplifies walking /proc/iomem. I personally
like the safety of the string just being the $driver component of the
name, but I won't lose sleep if the interface stays freeform like you
propose.

  reply index

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-30 10:29 [PATCH v2 0/3] mm/memory_hotplug: Allow to not create firmware memmap entries David Hildenbrand
2020-04-30 10:29 ` [PATCH v2 1/3] mm/memory_hotplug: Prepare passing flags to add_memory() and friends David Hildenbrand
2020-04-30 10:29 ` [PATCH v2 2/3] mm/memory_hotplug: Introduce MHP_NO_FIRMWARE_MEMMAP David Hildenbrand
2020-04-30 15:38   ` Eric W. Biederman
2020-04-30 15:52     ` David Hildenbrand
2020-04-30 16:04       ` Dave Hansen
2020-04-30 16:33       ` Eric W. Biederman
2020-04-30 16:49         ` David Hildenbrand
2020-04-30 18:06           ` Eric W. Biederman
2020-04-30 18:43             ` David Hildenbrand
2020-04-30 18:58               ` Dan Williams
2020-04-30 22:24               ` Andrew Morton
2020-05-01  9:34                 ` David Hildenbrand
2020-05-01 16:56                   ` Dan Williams
2020-05-01 17:21                     ` David Hildenbrand
2020-05-01 17:39                       ` Dan Williams
2020-05-01 17:45                         ` David Hildenbrand
2020-05-01 17:51                           ` David Hildenbrand
2020-05-01 18:03                             ` Dan Williams
2020-05-01 18:14                               ` David Hildenbrand
2020-05-01 18:43                                 ` Dan Williams
2020-05-01 19:17                                   ` David Hildenbrand
2020-05-01 20:12                                     ` Dan Williams
2020-05-01 21:10                                       ` David Hildenbrand
2020-05-01 21:52                                         ` Dan Williams
2020-05-02  9:26                                           ` David Hildenbrand
2020-05-02 18:03                                             ` Dan Williams [this message]
2020-04-30 10:29 ` [PATCH v2 3/3] device-dax: Add system ram (add_memory()) with MHP_NO_FIRMWARE_MEMMAP David Hildenbrand
2020-04-30 11:23   ` Dave Hansen
2020-04-30 15:28     ` David Hildenbrand

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAPcyv4iqwh6k40DUy-Pwi2h5pJm9vu7+JU1ghELy=3MGM1naNg@mail.gmail.com' \
    --to=dan.j.williams@intel.com \
    --cc=akpm@linux-foundation.org \
    --cc=bhe@redhat.com \
    --cc=dave.hansen@linux.intel.com \
    --cc=david@redhat.com \
    --cc=ebiederm@xmission.com \
    --cc=linux-acpi@vger.kernel.org \
    --cc=linux-hyperv@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-nvdimm@lists.01.org \
    --cc=linux-s390@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=mhocko@kernel.org \
    --cc=mhocko@suse.com \
    --cc=mst@redhat.com \
    --cc=pankaj.gupta.linux@gmail.com \
    --cc=richard.weiyang@gmail.com \
    --cc=virtio-dev@lists.oasis-open.org \
    --cc=virtualization@lists.linux-foundation.org \
    --cc=xen-devel@lists.xenproject.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-HyperV Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-hyperv/0 linux-hyperv/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-hyperv linux-hyperv/ https://lore.kernel.org/linux-hyperv \
		linux-hyperv@vger.kernel.org
	public-inbox-index linux-hyperv

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-hyperv


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git