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Re: [PATCH] docs: fix INTRODUCE description in xenstore.txt


  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • From: Jürgen Groß <jgross@xxxxxxxx>
  • Date: Thu, 6 Mar 2025 08:09:41 +0100
  • Autocrypt: addr=jgross@xxxxxxxx; keydata= xsBNBFOMcBYBCACgGjqjoGvbEouQZw/ToiBg9W98AlM2QHV+iNHsEs7kxWhKMjrioyspZKOB ycWxw3ie3j9uvg9EOB3aN4xiTv4qbnGiTr3oJhkB1gsb6ToJQZ8uxGq2kaV2KL9650I1SJve dYm8Of8Zd621lSmoKOwlNClALZNew72NjJLEzTalU1OdT7/i1TXkH09XSSI8mEQ/ouNcMvIJ NwQpd369y9bfIhWUiVXEK7MlRgUG6MvIj6Y3Am/BBLUVbDa4+gmzDC9ezlZkTZG2t14zWPvx XP3FAp2pkW0xqG7/377qptDmrk42GlSKN4z76ELnLxussxc7I2hx18NUcbP8+uty4bMxABEB AAHNH0p1ZXJnZW4gR3Jvc3MgPGpncm9zc0BzdXNlLmNvbT7CwHkEEwECACMFAlOMcK8CGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRCw3p3WKL8TL8eZB/9G0juS/kDY9LhEXseh mE9U+iA1VsLhgDqVbsOtZ/S14LRFHczNd/Lqkn7souCSoyWsBs3/wO+OjPvxf7m+Ef+sMtr0 G5lCWEWa9wa0IXx5HRPW/ScL+e4AVUbL7rurYMfwCzco+7TfjhMEOkC+va5gzi1KrErgNRHH kg3PhlnRY0Udyqx++UYkAsN4TQuEhNN32MvN0Np3WlBJOgKcuXpIElmMM5f1BBzJSKBkW0Jc Wy3h2Wy912vHKpPV/Xv7ZwVJ27v7KcuZcErtptDevAljxJtE7aJG6WiBzm+v9EswyWxwMCIO RoVBYuiocc51872tRGywc03xaQydB+9R7BHPzsBNBFOMcBYBCADLMfoA44MwGOB9YT1V4KCy vAfd7E0BTfaAurbG+Olacciz3yd09QOmejFZC6AnoykydyvTFLAWYcSCdISMr88COmmCbJzn sHAogjexXiif6ANUUlHpjxlHCCcELmZUzomNDnEOTxZFeWMTFF9Rf2k2F0Tl4E5kmsNGgtSa aMO0rNZoOEiD/7UfPP3dfh8JCQ1VtUUsQtT1sxos8Eb/HmriJhnaTZ7Hp3jtgTVkV0ybpgFg w6WMaRkrBh17mV0z2ajjmabB7SJxcouSkR0hcpNl4oM74d2/VqoW4BxxxOD1FcNCObCELfIS auZx+XT6s+CE7Qi/c44ibBMR7hyjdzWbABEBAAHCwF8EGAECAAkFAlOMcBYCGwwACgkQsN6d 1ii/Ey9D+Af/WFr3q+bg/8v5tCknCtn92d5lyYTBNt7xgWzDZX8G6/pngzKyWfedArllp0Pn fgIXtMNV+3t8Li1Tg843EXkP7+2+CQ98MB8XvvPLYAfW8nNDV85TyVgWlldNcgdv7nn1Sq8g HwB2BHdIAkYce3hEoDQXt/mKlgEGsLpzJcnLKimtPXQQy9TxUaLBe9PInPd+Ohix0XOlY+Uk QFEx50Ki3rSDl2Zt2tnkNYKUCvTJq7jvOlaPd6d/W0tZqpyy7KVay+K4aMobDsodB3dvEAs6 ScCnh03dDAFgIq5nsB11j3KPKdVoPlfucX2c7kGNH+LUMbzqV6beIENfNexkOfxHfw==
  • Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
  • Delivery-date: Thu, 06 Mar 2025 07:10:02 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 05.03.25 23:57, Andrew Cooper wrote:
On 05/03/2025 8:52 am, Juergen Gross wrote:
The description of the Xenstore INTRODUCE command is still referencing
xend. Fix that.

While at it, make clear that the Xenstore implementation is allowed
to ignore the specified gfn and use the Xenstore reserved grant id
GNTTAB_RESERVED_XENSTORE instead.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
  docs/misc/xenstore.txt | 6 +++++-
  1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/docs/misc/xenstore.txt b/docs/misc/xenstore.txt
index 38015835b1..d894d24d11 100644
--- a/docs/misc/xenstore.txt
+++ b/docs/misc/xenstore.txt
@@ -286,7 +286,7 @@ TRANSACTION_END             F|
  INTRODUCE             <domid>|<gfn>|<evtchn>|?
        Notifies xenstored to communicate with this domain.
- INTRODUCE is currently only used by xend (during domain
+       INTRODUCE is currently only used by xen tools (during domain
        startup and various forms of restore and resume), and
        xenstored prevents its use other than by dom0.
@@ -299,6 +299,10 @@ INTRODUCE <domid>|<gfn>|<evtchn>|?
        for example passing a high-bit-set 32-bit gfn as an unsigned
        decimal will attempt to use 0x7fffffff instead (!).
+ Xenstored might ignore the <gfn> value and use the reserved
+       grant table entry GNTTAB_RESERVED_XENSTORE instead for mapping
+       the Xenstore interface page of the guest.

I'd suggest making a stronger statement than this.

---
The <gfn> field is used by xenstoreds which use foreign mapping to
access the ring page.

Alternatively, Grant 1 (GNTTAB_RESERVED_XENSTORE) is reserved for the
same purpose, and is populated by the domain builder on behalf of the
guest.  This mechanism is preferred because reduces the permissions that
xenstored needs in order to function.

Both <gfn> and Grant 1 need to agree, because implementations of
xenstored will use one and ignore the other.

Fine with me.


Juergen

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