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From: Juergen Gross <jgross@suse.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: xen-devel@lists.xenproject.org, Ian Jackson <iwj@xenproject.org>,
	Wei Liu <wl@xen.org>, Julien Grall <julien@xen.org>
Subject: Re: [PATCH DNA 5/6] tools/xenstored: restore support for mapping ring as foreign memory
Date: Mon, 20 Sep 2021 12:51:55 +0200	[thread overview]
Message-ID: <1cff7e8e-613f-629e-99b9-0407767900ae@suse.com> (raw)
In-Reply-To: <YUhlfuPWEqnT0/42@MacBook-Air-de-Roger.local>


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On 20.09.21 12:42, Roger Pau Monné wrote:
> On Mon, Sep 20, 2021 at 10:24:45AM +0200, Juergen Gross wrote:
>> On 17.09.21 17:46, Roger Pau Monne wrote:
>>> Restore the previous way of mapping the xenstore ring using foreign
>>> memory. Use xenforeignmemory instead of libxc in order to avoid adding
>>> another dependency on a unstable interface.
>>
>> Mapping a guest page via xenforeignmemory is no good move IMO. A guest
>> not supporting a grant table for security reasons is a rather strange
>> idea, as it needs to trade that for a general memory access by any
>> backend without a way to restrict such accesses. This contradicts one
>> of the main concepts of the Xen security architecture.
> 
> I've done this in order to be able to assert that the switch to
> disable grant tables was working correctly, I don't intended this
> specific mode to be something that is desirable or that should be used
> in production, but I do think it's useful to be able to create such
> guests in order to assert that the option is taking effect.
> 
> The main problem of xenstore not being correctly initialized on a
> domain is that the "@introduceDomain" watch doesn't fire, and thus
> other components don't get notified of the newly created domain.
> 
> This seems to be a limitation of the current design, where the only
> way to get notifications of new domain creation is using
> "@introduceDomain", even when the caller doesn't care of whether the
> created domain as a working xenstore connection.
> 
> Maybe I can workaround this differently in xenstore, so that the watch
> fires even when the shared xenstore ring cannot be initialized.

Yes, I think this would be the way to go.


Juergen

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  reply	other threads:[~2021-09-20 10:52 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-17 15:46 [PATCH 0/6] gnttab: add per-domain controls Roger Pau Monne
2021-09-17 15:46 ` [PATCH 1/6] gnttab: allow setting max version per-domain Roger Pau Monne
2021-09-17 15:46 ` [PATCH 2/6] gnttab: allow per-domain control over transitive grants Roger Pau Monne
2021-09-20  9:32   ` Andrew Cooper
2021-09-20 11:45     ` Roger Pau Monné
2021-09-17 15:46 ` [PATCH 3/6] tools/console: use xenforeigmemory to map console ring Roger Pau Monne
2021-09-20 10:32   ` Ian Jackson
2021-09-17 15:46 ` [PATCH 4/6] tools/xenstored: use atexit to close interfaces Roger Pau Monne
2021-09-20  7:17   ` Roger Pau Monné
2021-09-20  9:22   ` Juergen Gross
2021-09-20 10:53     ` Roger Pau Monné
2021-09-20 10:57       ` Ian Jackson
2021-09-20 11:02         ` Juergen Gross
2021-09-20 12:21           ` Ian Jackson
2021-09-20 10:34   ` Ian Jackson
2021-09-20 10:39     ` Juergen Gross
2021-09-17 15:46 ` [PATCH DNA 5/6] tools/xenstored: restore support for mapping ring as foreign memory Roger Pau Monne
2021-09-20  8:24   ` Juergen Gross
2021-09-20 10:42     ` Roger Pau Monné
2021-09-20 10:51       ` Juergen Gross [this message]
2021-09-20 10:35   ` Ian Jackson
2021-09-17 15:46 ` [PATCH 6/6] gnttab: allow disabling grant table per-domain Roger Pau Monne
2021-09-17 16:06 ` [PATCH 0/6] gnttab: add per-domain controls Christian Lindig
2021-09-20  7:26   ` Roger Pau Monné
2021-09-20  8:24     ` Edwin Torok

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