From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50358) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Yz3NV-0002iA-TT for qemu-devel@nongnu.org; Sun, 31 May 2015 09:34:14 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Yz3NS-0003Qi-LE for qemu-devel@nongnu.org; Sun, 31 May 2015 09:34:13 -0400 Received: from mail-pd0-f181.google.com ([209.85.192.181]:33768) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Yz3NS-0003QV-Fj for qemu-devel@nongnu.org; Sun, 31 May 2015 09:34:10 -0400 Received: by pdbqa5 with SMTP id qa5so88321731pdb.0 for ; Sun, 31 May 2015 06:34:08 -0700 (PDT) Message-ID: <556B0DC9.7020901@ozlabs.ru> Date: Sun, 31 May 2015 23:34:01 +1000 From: Alexey Kardashevskiy MIME-Version: 1.0 References: <1432653754.11375.395.camel@redhat.com> In-Reply-To: <1432653754.11375.395.camel@redhat.com> Content-Type: text/plain; charset=koi8-r; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] VFIO use of HOST_PAGE_ALIGN List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex Williamson , Peter Crosthwaite Cc: Paolo Bonzini , Eric Auger , "qemu-devel@nongnu.org Developers" , Richard Henderson On 05/27/2015 01:22 AM, Alex Williamson wrote: > [cc +alexey] > > On Mon, 2015-05-25 at 00:48 -0700, Peter Crosthwaite wrote: >> Hi Alex and all, >> >> I am working on a patch series to enable multiple CPU architectures to >> run at once. It's a long story, but I have hit a snag in hw/vfio/pci.c >> which AFAICS is the only in-tree system-mode use of HOST_PAGE_ALIGN >> (all usermode code is a non-issue as not looking to support user-mode >> multi-arch yet). >> >> The problem I face, is that this macro depends on translate-all.c's >> qemu_host_page_size which in turn, depends on TARGET_PAGE_SIZE. I'm >> hoping that one day, TARGET_PAGE_SIZE will be a variable and the users >> of it will know to get the correct value depending on their CPU >> specific code location. vfio is the only one I can't handle. My >> knowledge on vfio is near-0, but my thinking is, since this is not >> arch specific code can we instead use the raw host page alignment >> rather that the CPU arch specific one? What is "raw host page" here? I thought qemu_host_page_size is the one, where does it depend on TARGET_PAGE_SIZE? > I think we could replace our use of HOST_PAGE_ALIGN with something based > only on the host's getpagesize(). I don't see that we really care about > the target page size for this usage. Alexey, I think you're the only > arch where host and target page sizes can actually be different, do you > agree? Thanks, Strongly agree. Where it really matters (MSIX), it is already qemu_host_page_size and HOST_PAGE_ALIGN and I am a bit scared by that "raw host page alignment" :) -- Alexey