From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754956AbbFBBkj (ORCPT ); Mon, 1 Jun 2015 21:40:39 -0400 Received: from ozlabs.org ([103.22.144.67]:44065 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753884AbbFBBkT (ORCPT ); Mon, 1 Jun 2015 21:40:19 -0400 Date: Tue, 2 Jun 2015 11:40:33 +1000 From: David Gibson To: Alexey Kardashevskiy Cc: linuxppc-dev@lists.ozlabs.org, Alex Williamson , Benjamin Herrenschmidt , Gavin Shan , Paul Mackerras , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH kernel v11 32/34] powerpc/mmu: Add userspace-to-physical addresses translation cache Message-ID: <20150602014033.GE3186@voom.fritz.box> References: <1432889098-22924-1-git-send-email-aik@ozlabs.ru> <1432889098-22924-33-git-send-email-aik@ozlabs.ru> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="+JUInw4efm7IfTNU" Content-Disposition: inline In-Reply-To: <1432889098-22924-33-git-send-email-aik@ozlabs.ru> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --+JUInw4efm7IfTNU Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, May 29, 2015 at 06:44:56PM +1000, Alexey Kardashevskiy wrote: > We are adding support for DMA memory pre-registration to be used in > conjunction with VFIO. The idea is that the userspace which is going to > run a guest may want to pre-register a user space memory region so > it all gets pinned once and never goes away. Having this done, > a hypervisor will not have to pin/unpin pages on every DMA map/unmap > request. This is going to help with multiple pinning of the same memory. >=20 > Another use of it is in-kernel real mode (mmu off) acceleration of > DMA requests where real time translation of guest physical to host > physical addresses is non-trivial and may fail as linux ptes may be > temporarily invalid. Also, having cached host physical addresses > (compared to just pinning at the start and then walking the page table > again on every H_PUT_TCE), we can be sure that the addresses which we put > into TCE table are the ones we already pinned. >=20 > This adds a list of memory regions to mm_context_t. Each region consists > of a header and a list of physical addresses. This adds API to: > 1. register/unregister memory regions; > 2. do final cleanup (which puts all pre-registered pages); > 3. do userspace to physical address translation; > 4. manage usage counters; multiple registration of the same memory > is allowed (once per container). >=20 > This implements 2 counters per registered memory region: > - @mapped: incremented on every DMA mapping; decremented on unmapping; > initialized to 1 when a region is just registered; once it becomes zero, > no more mappings allowe; > - @used: incremented on every "register" ioctl; decremented on > "unregister"; unregistration is allowed for DMA mapped regions unless > it is the very last reference. For the very last reference this checks > that the region is still mapped and returns -EBUSY so the userspace > gets to know that memory is still pinned and unregistration needs to > be retried; @used remains 1. >=20 > Host physical addresses are stored in vmalloc'ed array. In order to > access these in the real mode (mmu off), there is a real_vmalloc_addr() > helper. In-kernel acceleration patchset will move it from KVM to MMU code. >=20 > Signed-off-by: Alexey Kardashevskiy There's a bunch of ways this could be cleaned up, but those can be done later. So, Reviewed-by: David Gibson --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson --+JUInw4efm7IfTNU Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJVbQmRAAoJEGw4ysog2bOSzMsQAJlZUNMtTLvs1OHxMBvGXqu7 BTp+djsOO7pbWjT7DJZ4MhXGqAFdZSksyfAZ6q7Bi4IOnZPp7JuanwzlsnT+3n+M iANNbyq7wLoktOdj6cQjcOGRt2FZRD9HVmQyppUreYAytfH/SVBlhda/Xj5cXaTk U8QVs3HEoXYvZJN/0MQVCyLDzstHQMKg16U/4vrn/0No7vQTi3k+pEfF19FV8DsQ a/bhQsuu2+tfYOvQlSfD3KE6SQxYt6eM3n6fq8fejVYqulgS5gFvvCzXlhRDS9f3 uCIG9R4XHtwKHBINLf4v3RboBXRy24BmVT/+Tj7ECicbUzH7v0vfAHM6+crPa8OY Bs9lhNlQNPcOBvHGzgaV9B0w1BGhrdEmnW3b+fLHZnJpywCHZnVFra11/+fJFEX1 boMI8RAUxmtmxThb4hW0ITFj7bNwOfi6cj6/zcwYtHANpkd97R2CaBikNWXcTVol qERenPGDk6ighx8QekybKL2334hTZig3IIyYDbeGNfa3lfam7G7v5bVK7qjyXWTZ Qxu2aR34R4Z40QMRaGaTKzNkT2OrweOZrlo+hDJNDR+h7qHZn2KOy1mF34XDuhPB xz6AFq8SSPw+0XfxBfScaZuXMQf7oEXjjf2urr2C82G3QCcGQPw9VhwUztcMDCD1 ZrH/o4UHYoHcI3Vnu7W6 =xHH3 -----END PGP SIGNATURE----- --+JUInw4efm7IfTNU--