Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753436Ab3JDRXi (ORCPT ); Fri, 4 Oct 2013 13:23:38 -0400 Received: from va3ehsobe002.messaging.microsoft.com ([216.32.180.12]:51777 "EHLO va3outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752810Ab3JDRXg (ORCPT ); Fri, 4 Oct 2013 13:23:36 -0400 X-Forefront-Antispam-Report: CIP:70.37.183.190;KIP:(null);UIP:(null);IPV:NLI;H:mail.freescale.net;RD:none;EFVD:NLI X-SpamScore: -5 X-BigFish: VS-5(zz98dI9371I936eI542I1432I4015Izz1f42h208ch1ee6h1de0h1fdah2073h1202h1e76h1d1ah1d2ah1fc6hzz1de098h17326ah1de097h186068h8275bh8275dhz2dh2a8h839h8e2h8e3h93fhd25hf0ah1288h12a5h12a9h12bdh137ah13b6h1441h1504h1537h153bh15d0h162dh1631h1758h18e1h1946h19b5h19ceh1ad9h1b0ah1b2fh1fb3h1d0ch1d2eh1d3fh1dfeh1dffh1e1dh1fe8h1ff5hbe9i1155h) From: Bhushan Bharat-R65777 To: Alex Williamson CC: "joro@8bytes.org" , "benh@kernel.crashing.org" , "galak@kernel.crashing.org" , "linux-kernel@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-pci@vger.kernel.org" , "agraf@suse.de" , Wood Scott-B07421 , "iommu@lists.linux-foundation.org" Subject: RE: [PATCH 2/7] iommu: add api to get iommu_domain of a device Thread-Topic: [PATCH 2/7] iommu: add api to get iommu_domain of a device Thread-Index: AQHOtQsGaQsPvJ8CfEu+dkEJoOsdkZnWszeAgA2xFOCAAGMFgIAAC5rAgAAM6gCAAABh8A== Date: Fri, 4 Oct 2013 17:23:30 +0000 Message-ID: <6A3DF150A5B70D4F9B66A25E3F7C888D07191143@039-SN2MPN1-011.039d.mgd.msft.net> References: <1379575763-2091-1-git-send-email-Bharat.Bhushan@freescale.com> <1379575763-2091-3-git-send-email-Bharat.Bhushan@freescale.com> <1380127533.3030.319.camel@ul30vt.home> <6A3DF150A5B70D4F9B66A25E3F7C888D0718FD1C@039-SN2MPN1-011.039d.mgd.msft.net> <1380901507.2673.204.camel@ul30vt.home> <6A3DF150A5B70D4F9B66A25E3F7C888D07190F35@039-SN2MPN1-011.039d.mgd.msft.net> <1380906772.25705.19.camel@ul30vt.home> In-Reply-To: <1380906772.25705.19.camel@ul30vt.home> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [192.88.169.1] Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 X-OriginatorOrg: freescale.com X-FOPE-CONNECTOR: Id%0$Dn%*$RO%0$TLS%0$FQDN%$TlsDn% Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id r94HNpOj013291 Content-Length: 9080 Lines: 211 > -----Original Message----- > From: Alex Williamson [mailto:alex.williamson@redhat.com] > Sent: Friday, October 04, 2013 10:43 PM > To: Bhushan Bharat-R65777 > Cc: joro@8bytes.org; benh@kernel.crashing.org; galak@kernel.crashing.org; linux- > kernel@vger.kernel.org; linuxppc-dev@lists.ozlabs.org; linux- > pci@vger.kernel.org; agraf@suse.de; Wood Scott-B07421; iommu@lists.linux- > foundation.org > Subject: Re: [PATCH 2/7] iommu: add api to get iommu_domain of a device > > On Fri, 2013-10-04 at 16:47 +0000, Bhushan Bharat-R65777 wrote: > > > > > -----Original Message----- > > > From: Alex Williamson [mailto:alex.williamson@redhat.com] > > > Sent: Friday, October 04, 2013 9:15 PM > > > To: Bhushan Bharat-R65777 > > > Cc: joro@8bytes.org; benh@kernel.crashing.org; > > > galak@kernel.crashing.org; linux- kernel@vger.kernel.org; > > > linuxppc-dev@lists.ozlabs.org; linux- pci@vger.kernel.org; > > > agraf@suse.de; Wood Scott-B07421; iommu@lists.linux- foundation.org > > > Subject: Re: [PATCH 2/7] iommu: add api to get iommu_domain of a > > > device > > > > > > On Fri, 2013-10-04 at 09:54 +0000, Bhushan Bharat-R65777 wrote: > > > > > > > > > -----Original Message----- > > > > > From: linux-pci-owner@vger.kernel.org > > > > > [mailto:linux-pci-owner@vger.kernel.org] > > > > > On Behalf Of Alex Williamson > > > > > Sent: Wednesday, September 25, 2013 10:16 PM > > > > > To: Bhushan Bharat-R65777 > > > > > Cc: joro@8bytes.org; benh@kernel.crashing.org; > > > > > galak@kernel.crashing.org; linux- kernel@vger.kernel.org; > > > > > linuxppc-dev@lists.ozlabs.org; linux- pci@vger.kernel.org; > > > > > agraf@suse.de; Wood Scott-B07421; iommu@lists.linux- > > > > > foundation.org; Bhushan Bharat-R65777 > > > > > Subject: Re: [PATCH 2/7] iommu: add api to get iommu_domain of a > > > > > device > > > > > > > > > > On Thu, 2013-09-19 at 12:59 +0530, Bharat Bhushan wrote: > > > > > > This api return the iommu domain to which the device is attached. > > > > > > The iommu_domain is required for making API calls related to iommu. > > > > > > Follow up patches which use this API to know iommu maping. > > > > > > > > > > > > Signed-off-by: Bharat Bhushan > > > > > > --- > > > > > > drivers/iommu/iommu.c | 10 ++++++++++ > > > > > > include/linux/iommu.h | 7 +++++++ > > > > > > 2 files changed, 17 insertions(+), 0 deletions(-) > > > > > > > > > > > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > > > > > > index > > > > > > fbe9ca7..6ac5f50 100644 > > > > > > --- a/drivers/iommu/iommu.c > > > > > > +++ b/drivers/iommu/iommu.c > > > > > > @@ -696,6 +696,16 @@ void iommu_detach_device(struct > > > > > > iommu_domain *domain, struct device *dev) } > > > > > > EXPORT_SYMBOL_GPL(iommu_detach_device); > > > > > > > > > > > > +struct iommu_domain *iommu_get_dev_domain(struct device *dev) { > > > > > > + struct iommu_ops *ops = dev->bus->iommu_ops; > > > > > > + > > > > > > + if (unlikely(ops == NULL || ops->get_dev_iommu_domain == NULL)) > > > > > > + return NULL; > > > > > > + > > > > > > + return ops->get_dev_iommu_domain(dev); } > > > > > > +EXPORT_SYMBOL_GPL(iommu_get_dev_domain); > > > > > > > > > > What prevents this from racing iommu_domain_free()? There's no > > > > > references acquired, so there's no reason for the caller to > > > > > assume the > > > pointer is valid. > > > > > > > > Sorry for late query, somehow this email went into a folder and > > > > escaped; > > > > > > > > Just to be sure, there is not lock at generic "struct > > > > iommu_domain", but IP > > > specific structure (link FSL domain) linked in iommu_domain->priv > > > have a lock, so we need to ensure this race in FSL iommu code (say > > > drivers/iommu/fsl_pamu_domain.c), right? > > > > > > No, it's not sufficient to make sure that your use of the interface > > > is race free. The interface itself needs to be designed so that > > > it's difficult to use incorrectly. > > > > So we can define iommu_get_dev_domain()/iommu_put_dev_domain(); > > iommu_get_dev_domain() will return domain with the lock held, and > > iommu_put_dev_domain() will release the lock? And > > iommu_get_dev_domain() must always be followed by > > iommu_get_dev_domain(). > > What lock? get/put are generally used for reference counting, not locking in > the kernel. > > > > That's not the case here. This is a backdoor to get the iommu > > > domain from the iommu driver regardless of who is using it or how. > > > The iommu domain is created and managed by vfio, so shouldn't we be > > > looking at how to do this through vfio? > > > > Let me first describe what we are doing here: > > During initialization:- > > - vfio talks to MSI system to know the MSI-page and size > > - vfio then interacts with iommu to map the MSI-page in iommu (IOVA > > is decided by userspace and physical address is the MSI-page) > > - So the IOVA subwindow mapping is created in iommu and yes VFIO know about > this mapping. > > > > Now do SET_IRQ(MSI/MSIX) ioctl: > > - calls pci_enable_msix()/pci_enable_msi_block(): which is supposed to set > MSI address/data in device. > > - So in current implementation (this patchset) msi-subsystem gets the IOVA > from iommu via this defined interface. > > - Are you saying that rather than getting this from iommu, we should get this > from vfio? What difference does this make? > > Yes, you just said above that vfio knows the msi to iova mapping, so why go > outside of vfio to find it later? The difference is one case you can have a > proper reference to data structures to make sure the pointer you get back > actually has meaning at the time you're using it vs the code here where you're > defining an API that returns a meaningless value With FSL-PAMU we will always get consistant data from iommu or vfio-data structure. > because you can't check or > enforce that an arbitrary caller is using it correctly. I am not sure what is arbitrary caller? pdev is known to vfio, so vfio will only make pci_enable_msix()/pci_enable_msi_block() for this pdev. If anyother code makes then it is some other unexpectedly thing happening in system, no? > It's not maintainable. > Thanks, I do not have any issue with this as well, can you also describe the type of API you are envisioning; I can think of defining some function in vfio.c/vfio_iommu*.c, make them global and declare then in include/Linux/vfio.h And include in caller file (arch/powerpc/kernel/msi.c) Thanks -Bharat > > Alex > > > > It seems like you'd want to use your device to get a vfio group > > > reference, from which you could do something with the vfio external > > > user interface and get the iommu domain reference. Thanks, > > > > > > Alex > > > > > > > > > /* > > > > > > * IOMMU groups are really the natrual working unit of the IOMMU, but > > > > > > * the IOMMU API works on domains and devices. Bridge that > > > > > > gap by diff --git a/include/linux/iommu.h > > > > > > b/include/linux/iommu.h index 7ea319e..fa046bd 100644 > > > > > > --- a/include/linux/iommu.h > > > > > > +++ b/include/linux/iommu.h > > > > > > @@ -127,6 +127,7 @@ struct iommu_ops { > > > > > > int (*domain_set_windows)(struct iommu_domain *domain, u32 > > > w_count); > > > > > > /* Get the numer of window per domain */ > > > > > > u32 (*domain_get_windows)(struct iommu_domain *domain); > > > > > > + struct iommu_domain *(*get_dev_iommu_domain)(struct device > > > > > > +*dev); > > > > > > > > > > > > unsigned long pgsize_bitmap; }; @@ -190,6 +191,7 @@ extern > > > > > > int iommu_domain_window_enable(struct iommu_domain > > > > > *domain, u32 wnd_nr, > > > > > > phys_addr_t offset, u64 size, > > > > > > int prot); > > > > > > extern void iommu_domain_window_disable(struct iommu_domain > > > > > > *domain, > > > > > > u32 wnd_nr); > > > > > > +extern struct iommu_domain *iommu_get_dev_domain(struct > > > > > > +device *dev); > > > > > > /** > > > > > > * report_iommu_fault() - report about an IOMMU fault to the > > > > > > IOMMU > > > framework > > > > > > * @domain: the iommu domain where the fault has happened @@ > > > > > > -284,6 > > > > > > +286,11 @@ static inline void > > > > > > +iommu_domain_window_disable(struct > > > > > > iommu_domain *domain, { } > > > > > > > > > > > > +static inline struct iommu_domain > > > > > > +*iommu_get_dev_domain(struct device > > > > > > +*dev) { > > > > > > + return NULL; > > > > > > +} > > > > > > + > > > > > > static inline phys_addr_t iommu_iova_to_phys(struct > > > > > > iommu_domain *domain, dma_addr_t iova) { > > > > > > return 0; > > > > > > > > > > > > > > > > > > > > -- > > > > > To unsubscribe from this list: send the line "unsubscribe linux-pci" > > > > > in the body of a message to majordomo@vger.kernel.org More > > > > > majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > > > > > > > > > > > > > > ????{.n?+???????+%?????ݶ??w??{.n?+????{??G?????{ay?ʇڙ?,j??f???h?????????z_??(?階?ݢj"???m??????G????????????&???~???iO???z??v?^?m???? ????????I?