From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51458) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XXPHc-0002wD-J0 for qemu-devel@nongnu.org; Fri, 26 Sep 2014 02:45:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XXPHT-0007zc-8a for qemu-devel@nongnu.org; Fri, 26 Sep 2014 02:45:36 -0400 Received: from e06smtp12.uk.ibm.com ([195.75.94.108]:33202) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XXPHS-0007yJ-Rd for qemu-devel@nongnu.org; Fri, 26 Sep 2014 02:45:27 -0400 Received: from /spool/local by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 26 Sep 2014 07:45:19 +0100 Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by d06dlp03.portsmouth.uk.ibm.com (Postfix) with ESMTP id 0EFE21B08023 for ; Fri, 26 Sep 2014 07:46:26 +0100 (BST) Received: from d06av03.portsmouth.uk.ibm.com (d06av03.portsmouth.uk.ibm.com [9.149.37.213]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id s8Q6jFup47841394 for ; Fri, 26 Sep 2014 06:45:15 GMT Received: from d06av03.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av03.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s8Q6jFJe031532 for ; Fri, 26 Sep 2014 00:45:15 -0600 Date: Fri, 26 Sep 2014 08:45:14 +0200 From: Frank Blaschka Message-ID: <20140926064514.GA13550@tuxmaker.boeblingen.de.ibm.com> References: <20140919115429.557279920@de.ibm.com> <1411418851.1199.137.camel@ul30vt.home> <20140924084727.GA17378@tuxmaker.boeblingen.de.ibm.com> <1411574757.24563.101.camel@ul30vt.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1411574757.24563.101.camel@ul30vt.home> Subject: Re: [Qemu-devel] [RFC patch 0/6] vfio based pci pass-through for qemu/KVM on s390 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex Williamson Cc: linux-s390@vger.kernel.org, frank.blaschka@de.ibm.com, kvm@vger.kernel.org, agraf@suse.de, qemu-devel@nongnu.org, pbonzini@redhat.com On Wed, Sep 24, 2014 at 10:05:57AM -0600, Alex Williamson wrote: > On Wed, 2014-09-24 at 10:47 +0200, Frank Blaschka wrote: > > On Mon, Sep 22, 2014 at 02:47:31PM -0600, Alex Williamson wrote: > > > On Fri, 2014-09-19 at 13:54 +0200, frank.blaschka@de.ibm.com wrote: > > > > This set of patches implements a vfio based solution for pci > > > > pass-through on the s390 platform. The kernel stuff is pretty > > > > much straight forward, but qemu needs more work. > > > > > > > > Most interesting patch is: > > > > vfio: make vfio run on s390 platform > > > > > > > > I hope Alex & Alex can give me some guidance how to do the changes > > > > in an appropriate way. After creating a separate iommmu address space > > > > for each attached PCI device I can successfully run the vfio type1 > > > > iommu. So If we could extend type1 not registering all guest memory > > > > (see patch) I think we do not need a special vfio iommu for s390 > > > > for the moment. > > > > > > > > The patches implement the base pass-through support. s390 specific > > > > virtualization functions are currently not included. This would > > > > be a second step after the base support is done. > > > > > > > > kernel patches apply to linux-kvm-next > > > > > > > > KVM: s390: Enable PCI instructions > > > > iommu: add iommu for s390 platform > > > > vfio: make vfio build on s390 > > > > > > > > qemu patches apply to qemu-master > > > > > > > > s390: Add PCI bus support > > > > s390: implement pci instruction > > > > vfio: make vfio run on s390 platform > > > > > > > > Thx for feedback and review comments > > > > > > Sending patches as attachments makes it difficult to comment inline. > > > > > Sorry, don't understand this. I sent every patch as separate email so > > you can comment directly on the patch. What do you prefer? > > The patches in each email are showing up as attachments in my mail > client. Is it just me? > > > > 2/6 > > > - careful of the namespace as you're changing functions from static and > > > exporting them > > > - doesn't seem like functions need to be exported, just non-static to > > > call from s390-iommu.c > > > > > Ok, will change this. > > > > > 6/6 > > > - We shouldn't need to globally disable mmap, each VFIO region reports > > > whether it supports mmap and vfio-pci on s390 should indicate mmap is > > > not supported on the platform. > > Yes, this is even better to let the kernel announce a BAR can not be > > mmap'ed. Checking the kernel code I realized the BARs are valid for > > mmap'ing but the s390 platform does simply not allow this. So I feal we > > have to introduce a platform switch in kernel. How about this ... > > > > --- a/drivers/vfio/pci/vfio_pci.c > > +++ b/drivers/vfio/pci/vfio_pci.c > > @@ -377,9 +377,11 @@ static long vfio_pci_ioctl(void *device_ > > > > info.flags = VFIO_REGION_INFO_FLAG_READ | > > VFIO_REGION_INFO_FLAG_WRITE; > > +#ifndef CONFIG_S390 > > if (pci_resource_flags(pdev, info.index) & > > IORESOURCE_MEM && info.size >= PAGE_SIZE) > > info.flags |= VFIO_REGION_INFO_FLAG_MMAP; > > +#endif > > break; > > case VFIO_PCI_ROM_REGION_INDEX: > > { > > Maybe pull it out into a function. Also, is there some capability or > feature we can test rather than just the architecture? I'd prefer it to > be excluded because of a platform feature that prevents it rather than > the overall architecture itself. > Ok, understand this. There is no capability of feature so I will go with the function. > > > - INTx should be done the same way, the interrupt index for INTx should > > > report 0 count. The current code likely doesn't handle this, but it > > > should be easy to fix. > > The current code is fine. Problem is the card reports an interrupt index > > (PCI_INTERRUPT_PIN) but again the platform does not support INTx at all. > > So we need a platform switch as well. > > Yep, let's try to do something consistent with the MMAP testing. > Do you mean let the kernel announce this also? > > > - s390_msix_notify() vs msix_notify() should be abstracted somewhere > > > > Platform does not have have an apic so there is nothing we could emulate > > in qemu to make the existing msix_notify() work. > > > > > else. How would an emulated PCI device with MSI-X support work? > > > - same for add_msi_route > > Same here, we have to setup an adapter route due to the fact MSIX > > notifications are delivered as adapter/thin IRQs on the platform. > > > > Any suggestion or idea how a better abstraction could look like? > > > > With all the platform constraints I was not able to find a suitable > > emulated device. Remember s390: > > - does not support IO BARs > > - does not support INTx only MSIX > > What about MSI (non-X)? In theory MSI should work also but I have not seen in reality. > > > - in reality currently there is only a PCI network card available > > On the physical hardware? > yes > > - platform does not support fancy I/O like usb or audio :-) > > So we don't even have kernel (host and guest) support for this > > kind of devices. > > Does that mean you couldn't? What about virtio-net-pci with MSI-X > interrupts or emulated xhci with MSI-X interrupts, couldn't those be > supported if s390 MSI-X were properly integrated into the QEMU MSI-X > API? vfio-pci isn't the right level to be switching between the > standard API and the s390 API. > Yes, I also think vfio might not be the best place to switch API. Will try to move s390 specifics to MSI-X level. > > > - We can probably come up with a better way to determine which address > > > space to connect to the memory listener. > > Any suggestion or idea for that? > > I imagine you can tell by the address space of the device whether it > lives behind an emulated IOMMU or not and therefore pick the closest > address space for the notifier, the IOMMU or the system. Thanks, > I do not undertand this in detail, can you elaborate a little bit more on this? Or maybe provide a code snip? Thx Frank > Alex > >