All of lore.kernel.org
 help / color / mirror / Atom feed
From: Ian Jackson <Ian.Jackson@eu.citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Wei Liu <wei.liu2@citrix.com>,
	Ian Campbell <ian.campbell@citrix.com>,
	Razvan Cojocaru <rcojocaru@bitdefender.com>,
	Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
	George Dunlap <george.dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Stefano Stabellini <stefano.stabellini@citrix.com>,
	Tamas Lengyel <tlengyel@novetta.com>,
	xen-devel@lists.xenproject.org, KeirFraser <keir@xen.org>
Subject: Re: [PATCH v2 1/2] altp2m: Merge p2m_set_altp2m_mem_access and p2m_set_mem_access
Date: Mon, 1 Feb 2016 16:58:50 +0000	[thread overview]
Message-ID: <22191.36554.310417.255788@mariner.uk.xensource.com> (raw)
In-Reply-To: <56AF985A02000078000CD1FA@prv-mh.provo.novell.com>

Jan Beulich writes ("Re: [PATCH v2 1/2] altp2m: Merge p2m_set_altp2m_mem_access and p2m_set_mem_access"):
> On 01.02.16 at 16:22, <Ian.Jackson@eu.citrix.com> wrote:
> > It's not like we're short of memory op values.
> 
> Are we not? They need to fit in 6 bits (unless we want to play tricks),
> and numbers up to 27 are already in use.

Maybe I am confused.  It's hard to make sense of the actual ABI which
doesn't seem to be documented yet.

...

I have just read the docs some more and found this:

  /*
   * To allow safe resume of do_memory_op() after preemption, we need
   * to know at what point in the page list to resume. For this
   * purpose I steal the high-order bits of the @cmd parameter, which
   * are otherwise unused and zero.
   *
   * Note that both of these values are effectively part of the ABI,
   * even if we don't need to make them a formal part of it: A guest
   * suspended for migration in the middle of a continuation would
   * fail to work if resumed on a hypervisor using different values.
   */
  #define MEMOP_EXTENT_SHIFT 6 /* cmd[:6] == start_extent */
  #define MEMOP_CMD_MASK     ((1 << MEMOP_EXTENT_SHIFT) - 1)

Urrrrggh!

If we run out of memory_op numbers, can't we just invent a new
hypercall ?

Ian.

  reply	other threads:[~2016-02-01 16:58 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-28 20:58 [PATCH v2 1/2] altp2m: Merge p2m_set_altp2m_mem_access and p2m_set_mem_access Tamas K Lengyel
2016-01-28 20:58 ` [PATCH v2 2/2] altp2m: Implement p2m_get_mem_access for altp2m views Tamas K Lengyel
2016-01-29 11:03 ` [PATCH v2 1/2] altp2m: Merge p2m_set_altp2m_mem_access and p2m_set_mem_access Jan Beulich
2016-01-29 16:12   ` Lengyel, Tamas
2016-01-29 16:19     ` Jan Beulich
2016-01-29 16:32       ` Lengyel, Tamas
2016-01-29 16:47         ` Jan Beulich
2016-02-01 14:45           ` Ian Campbell
2016-02-01 15:22             ` Ian Jackson
2016-02-01 16:39               ` Jan Beulich
2016-02-01 16:58                 ` Ian Jackson [this message]
2016-02-01 17:03                   ` Jan Beulich
2016-02-01 16:21             ` Jan Beulich
2016-02-01 16:30               ` Ian Campbell
2016-02-01 16:35                 ` Lengyel, Tamas
2016-02-01 16:41                   ` Jan Beulich
2016-02-01 16:36                 ` Jan Beulich
2016-02-01 16:36               ` Lengyel, Tamas
2016-02-01 11:02 ` Wei Liu

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=22191.36554.310417.255788@mariner.uk.xensource.com \
    --to=ian.jackson@eu.citrix.com \
    --cc=JBeulich@suse.com \
    --cc=andrew.cooper3@citrix.com \
    --cc=george.dunlap@eu.citrix.com \
    --cc=ian.campbell@citrix.com \
    --cc=keir@xen.org \
    --cc=rcojocaru@bitdefender.com \
    --cc=stefano.stabellini@citrix.com \
    --cc=stefano.stabellini@eu.citrix.com \
    --cc=tlengyel@novetta.com \
    --cc=wei.liu2@citrix.com \
    --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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.