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a=rsa-sha256; c=relaxed/relaxed; d= invisiblethingslab.com; h=cc:cc:content-type:date:date:from:from :in-reply-to:message-id:mime-version:reply-to:sender:subject :subject:to:to; s=fm1; t=1652544389; x=1652630789; bh=dl1KQYoQor 7dFAFhpdtNa+47JnMIBmQHVAoY4PnaKqo=; b=WnlthM3QMFEj+Xq1OpWQEBjXhn Zt9iXKJXoLPTs78znRUeUZuvpieT3yiMv+PxzvZm51zjeFyuFH3+ddcMkaRKXttE keBOGVqhJDhH/jkpT9dWyOL5/B+PVdXYL065XT/xW/QzXYkPNFceXa6YoBqLn+UU /NjBicpatJFwFsd22aozATMNCbRiIdzNXfR2joBb2sz+E8HAMC0AuYaDcKIdws5b 8m4Xj4cLXwJYEBjQPcr6W2T8eqWeapQx6YK+w1mvcAWLzLdOMgqAC4blFmobjTuo HLQsEbfKHObprXjc8XoHqIegtoZt32Tq4gM9svo6Hx3DMqYBlro4I/bYtZZA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:date:date:from:from :in-reply-to:message-id:mime-version:reply-to:sender:subject :subject:to:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm1; t=1652544389; x=1652630789; bh=dl1KQYoQor7dF AFhpdtNa+47JnMIBmQHVAoY4PnaKqo=; b=JFVIQTw60eGO61Ai9EOiGrGqPkes0 WzDU0eDlZK2DRQGqt/UZJg+hHrpIW59ZPU2XqAgKEyK4z3mOxfLTiovRQ5TLmiQW 1DD4LdLtSA4ki09d2uBqkBJxLhbb+lXrpr7IYdnRxtJcjTM+QNcvJDn2bwT+atkL Kb39ege6Ta0USh0tZkSqPaB1YHIpG7QAWxrlirYrp0OJ/Z6iTgvhMLF22Djc1OrH PO3pa67ygpqtdBzzE9blGGJ19ajMUfYOS161NGrxUEiJFuMdtink6SVUIc+1+zbb /XBH5EnQF1pMigQnDb5CSC5GCBTWj98raQeSgqDiHItYoc1xpr/ZIxeUA== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvfedrhedugdelhecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenuc fjughrpeffhffvvefukfggtggusehgtderredttdejnecuhfhrohhmpeffvghmihcuofgr rhhivgcuqfgsvghnohhurhcuoeguvghmihesihhnvhhishhisghlvghthhhinhhgshhlrg gsrdgtohhmqeenucggtffrrghtthgvrhhnpeevieefgeeuhefhjedutdejuefhudetveeg geeitddujeelteekgeeigedtteekgeenucffohhmrghinhepghhithhhuhgsrdgtohhmne cuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrhhomhepuggvmhhi sehinhhvihhsihgslhgvthhhihhnghhslhgrsgdrtghomh X-ME-Proxy: Date: Sat, 14 May 2022 11:55:39 -0400 From: Demi Marie Obenour To: Xen developer discussion Cc: Juergen Gross , Boris Ostrovski , Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= , linux-kernel@vger.kernel.org Subject: Hang in 5.17.4+ that appears to be due to Xen Message-ID: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="TNAwTdkDEjbbq6M1" Content-Disposition: inline --TNAwTdkDEjbbq6M1 Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Sat, 14 May 2022 11:55:39 -0400 From: Demi Marie Obenour To: Xen developer discussion Cc: Juergen Gross , Boris Ostrovski , Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= , linux-kernel@vger.kernel.org Subject: Hang in 5.17.4+ that appears to be due to Xen In https://github.com/QubesOS/qubes-issues/issues/7481, a user reported that Xorg locked up when resizing a VM window. While I do not have the same hardware the user does and thus cannot reproduce the bug, the stack trace seems to indicate a deadlock between xen_gntdev and i915. It appears that gnttab_unmap_refs_sync() is waiting for i915 to free the pages, while i915 is waiting for the MMU notifier that called gnttab_unmap_refs_sync() to return. Result: deadlock. The problem appears to be that a mapped grant in PV mode will stay in the =E2=80=9Cinvalidating=E2=80=9D state until it is freed. While MMU noti= fiers are allowed to sleep, it appears that they cannot wait for the page to be freed, as is happening here. That said, I am not very familiar with this code, so my diagnosis might be incorrect. --=20 Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab --TNAwTdkDEjbbq6M1 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEdodNnxM2uiJZBxxxsoi1X/+cIsEFAmJ/04MACgkQsoi1X/+c IsGi2hAArO7G1fAnno/7xTzDfqxcNnOEuHFwZcn55O1E0JJ6qjGj9Uc98Td3TAcw M2i9U0fDpAB3L9naiD86fZHTgbKhEHAJ3d8D7RzA8wLOCdYD5Swh2rib2smYgZHP 7Lsl9IhcMhc0JkgwJ0Acr7qnA/2bar8uz3q4hX/aEiHJo+nD/PvrLnhXYNrfSUHK zP4ceuHJ2DYMBMEE66kdcolWYB2md5oOJXf1ff8MIiGAfxlaAqfBpCTInD6Fx060 SM8JBnDkoDkp8lyMpoklyN0wwtParAdYpQ4au70NctQ0ImQtcEtx8YKQI1qkyCUy oXDX8LwVb4YNpu1/wtfKwM4M2q4zKqvPLRjGA2TVKPOv4fPBw2+3GyhmOPwQDn19 LSbwnBo0mFb05bjQFKHf7sEhFmKZ63Gr2RlU+91tjVaquRQILd5CFW/0wCaNvDhq 6+t28vOl/loFBoQo0OCXL1KMgKQjtPcj+Kd8OflFuOceuD+4L7KzZ2EpUHOTD+V5 q+qchLFuJ9ic0Ohy+m4J1aU0t2Hjk5iyD//lrlA1iWhSM15F0PEPzRbeO02DT0Js bTKbIx62lTo5NHrB6AcHWYUsX9wN51+Kb7/ca/vNVD1gQJPgFaooNnNv2fK0z0ND jGcmREAkW9MAGOovIwBHEU68Ibr0bvwgf5jrcJWERKtOPQXVHs4= =i937 -----END PGP SIGNATURE----- --TNAwTdkDEjbbq6M1--