From mboxrd@z Thu Jan 1 00:00:00 1970 From: Janosch Frank Subject: Re: [RFC/PATCH v2 03/22] s390/mm: add gmap PMD invalidation notification Date: Mon, 22 Jan 2018 15:04:56 +0100 Message-ID: References: <1513169613-13509-1-git-send-email-frankja@linux.vnet.ibm.com> <1513169613-13509-4-git-send-email-frankja@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="zYqKMyGuf3U7KHBwgIanwQM0u0yNpQ0cw" Return-path: In-Reply-To: Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: David Hildenbrand , kvm@vger.kernel.org Cc: schwidefsky@de.ibm.com, borntraeger@de.ibm.com, dominik.dingel@gmail.com, linux-s390@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --zYqKMyGuf3U7KHBwgIanwQM0u0yNpQ0cw Content-Type: multipart/mixed; boundary="m3zn9fQuQCpHfNbN6IAOQ8WhSRIkxNfsT"; protected-headers="v1" From: Janosch Frank To: David Hildenbrand , kvm@vger.kernel.org Cc: schwidefsky@de.ibm.com, borntraeger@de.ibm.com, dominik.dingel@gmail.com, linux-s390@vger.kernel.org Message-ID: Subject: Re: [RFC/PATCH v2 03/22] s390/mm: add gmap PMD invalidation notification References: <1513169613-13509-1-git-send-email-frankja@linux.vnet.ibm.com> <1513169613-13509-4-git-send-email-frankja@linux.vnet.ibm.com> In-Reply-To: --m3zn9fQuQCpHfNbN6IAOQ8WhSRIkxNfsT Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 22.01.2018 14:29, David Hildenbrand wrote: > On 22.01.2018 14:13, Janosch Frank wrote: >> On 22.01.2018 12:46, David Hildenbrand wrote: >>> On 13.12.2017 13:53, Janosch Frank wrote: >>>> For later migration of huge pages we want to write-protect guest >>>> PMDs. While doing this, we have to make absolutely sure, that the >>>> guest's lowcore is always accessible when the VCPU is running. With >>>> PTEs, this is solved by marking the PGSTEs of the lowcore pages with= >>>> the invalidation notification bit and kicking the guest out of the S= IE >>>> via a notifier function if we need to invalidate such a page. >>>> >>>> With PMDs we do not have PGSTEs or some other bits we could use in t= he >>>> host PMD. Instead we pick one of the free bits in the gmap PMD. Ever= y >>>> time a host pmd will be invalidated, we will check if the respective= >>>> gmap PMD has the bit set and in that case fire up the notifier. >>>> >>>> In the first step we only support setting the invalidation bit, but = we >>>> do not support restricting access of guest pmds. It will follow >>>> shortly. >>> >>> I am wondering if we could avoid having invalidation bits on PMDs >>> completely by always splitting up a PMD huge page into PTEs. >>> >>> I assume this would make the code easier - as we need split up of PMD= s >>> either way when protecting for the shadow gmap. >>> >>> This would imply that also our notification handler only has to be >>> called for 4k pages, which also makes that part easier. >> >> Except for 1MB shadowed segments which still need an invalidation hand= ler. >=20 > But that doesn't go via gmap_protect_range() / gmap_call_notifier() if = I > am not mistaking. Yes, my point was that we'd still need pmdp_notify. --m3zn9fQuQCpHfNbN6IAOQ8WhSRIkxNfsT-- --zYqKMyGuf3U7KHBwgIanwQM0u0yNpQ0cw Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJaZe+IAAoJEBcO/8Q8ZEV5BUMQAKRr68C+9mKeOxWMW8n7Aw8c G1o/xESaynnfu76FjyYvNlep3cQgfXfQnhOmsykKBwB6d0jBPHI7FdYjRfHAKOBP ydWvMi/+JuppPW0Fcc0QMiFk8a1sB7fjmx6cAfROZUuAeiHZqcBFXWBvB7tTt7IW K0jpvj4zXjq6j5DJscJTAEM+oA/nW5CCBDNtrJNHpNNV2lhveT62zFyIuxaU6Prr YujfObEEiubJLOKKKcpqG4ybdV10d5Qe8lnobudgjrcydUgwGzDakmfc/f43mtRK eyFqjaiZ8v+oZ06REuHT6qnzZHWFIX3lFvbcWpPpYZhyrxwmHs9Xr6nx97hJyva6 mg1dBnpboUU7jsZLZ3ZWp5+G1DYS4gJ1NRjrGQb1AX/hGnFcOSWk+nPnSV2t7iVK 3/nCnJ3UKRDbnjy8PgkN44KpEbcK5YlBQdH0kMeJNGCxMRAUlezZH97Xv2BYlAHe Iiy5GEsnDxJ6NVEcMqdN1yNqETd5WS3GFR1HiznmrdBY1qVm1dzpJtWH9DZoM1Ye 0TlWDSgIfGyYYnHiZEm+j6aFOOeaTchJIY6bC0QOUPvtGrWU899i7iVvCm0RM5BO NQ9biowPXUBHCqE2eEtboM5D08GNpZdRhVUrA/Q0Id/5N/JC20sAx5F+XRnHlJUg dS0eUW52o4XIY88i2fpY =I62F -----END PGP SIGNATURE----- --zYqKMyGuf3U7KHBwgIanwQM0u0yNpQ0cw--