From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olaf Hering Subject: Re: [PATCH 0/2] MMIO emulation fixes Date: Wed, 29 Aug 2018 13:00:52 +0200 Message-ID: <20180829110052.GC31376@aepfle.de> References: <5B6DAF9F02000078001DD040@prv1-mh.provo.novell.com> <5B6DB69D02000078001DD06A@prv1-mh.provo.novell.com> <92ca69e5-98b1-61e4-817a-3868f829471a@citrix.com> <5B712A3502000078001DD514@prv1-mh.provo.novell.com> <20180829103614.GA31376@aepfle.de> <75009cae-1c9b-65d9-8269-497f94469983@citrix.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============9071230856918192320==" Return-path: Received: from us1-rack-dfw2.inumbo.com ([104.130.134.6]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1fuyDa-0002AV-Tu for xen-devel@lists.xenproject.org; Wed, 29 Aug 2018 11:00:59 +0000 In-Reply-To: <75009cae-1c9b-65d9-8269-497f94469983@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" To: Andrew Cooper Cc: George Dunlap , xen-devel , Paul Durrant , george.dunlap@citrix.com, Jan Beulich List-Id: xen-devel@lists.xenproject.org --===============9071230856918192320== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="jousvV0MzM2p6OtC" Content-Disposition: inline --jousvV0MzM2p6OtC Content-Type: text/plain; charset=utf-8 Content-Disposition: inline On Wed, Aug 29, Andrew Cooper wrote: > Architecturally speaking, handing #MC back is probably the closest we > can get to sensible behaviour, but it is still a bug that Linux is > touching the ballooned out page in the first place. Well, the issue is that a read crosses a page boundary. If that would be forbidden, load_unaligned_zeropad() would not exist. It can not know what is in the following page. And such page crossing happens also in the unballooned case. Sadly I can not trigger the reported NFS bug myself. But it can be enforced by ballooning enough pages so that an allocated readdir reply eventually is right in front of a ballooned page. Olaf --jousvV0MzM2p6OtC Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iF0EARECAB0WIQSkRyP6Rn//f03pRUBdQqD6ppg2fgUCW4Z84QAKCRBdQqD6ppg2 fp25AJ9W9FgX9595utSXicONFLK6L88fWwCdEUnP48iIKisj450mLwRDnUKpI9o= =IrIQ -----END PGP SIGNATURE----- --jousvV0MzM2p6OtC-- --===============9071230856918192320== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KWGVuLWRldmVs IG1haWxpbmcgbGlzdApYZW4tZGV2ZWxAbGlzdHMueGVucHJvamVjdC5vcmcKaHR0cHM6Ly9saXN0 cy54ZW5wcm9qZWN0Lm9yZy9tYWlsbWFuL2xpc3RpbmZvL3hlbi1kZXZlbA== --===============9071230856918192320==--