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Message-ID: <6A3DF150A5B70D4F9B66A25E3F7C888D071C0A84@039-SN2MPN1-013.039d.mgd.msft.net>
Date: Wed, 16 Oct 2013 17:21:59 +0000
From: Bhushan Bharat-R65777 <R65777@...escale.com>
To: Sethi Varun-B16395 <B16395@...escale.com>,
"joro@...tes.org" <joro@...tes.org>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Yoder Stuart-B08248 <B08248@...escale.com>,
Wood Scott-B07421 <B07421@...escale.com>,
"alex.williamson@...hat.com" <alex.williamson@...hat.com>
Subject: RE: [PATCH 2/3 v2] iommu/fsl: Enable default DMA window for PCIe
devices
> >
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Sethi Varun-B16395
> > > > > Sent: Wednesday, October 16, 2013 4:53 PM
> > > > > To: joro@...tes.org; iommu@...ts.linux-foundation.org; linuxppc-
> > > > > dev@...ts.ozlabs.org; linux-kernel@...r.kernel.org; Yoder
> > > > > Stuart-B08248; Wood Scott-B07421; alex.williamson@...hat.com;
> > > > > Bhushan
> > > > > Bharat-R65777
> > > > > Cc: Sethi Varun-B16395
> > > > > Subject: [PATCH 2/3 v2] iommu/fsl: Enable default DMA window for
> > > > > PCIe devices
> > > > >
> > > > > Once the PCIe device assigned to a guest VM (via VFIO) gets
> > > > > detached from the iommu domain (when guest terminates), its PAMU
> > > > > table entry is disabled. So, this would prevent the device from
> > > > > being used once it's
> > > > assigned back to the host.
> > > > >
> > > > > This patch allows for creation of a default DMA window
> > > > > corresponding to the device and subsequently enabling the PAMU
> > > > > table entry. Before we enable the entry, we ensure that the
> > > > > device's bus master capability is disabled (device quiesced).
> > > > >
> > > > > Signed-off-by: Varun Sethi <Varun.Sethi@...escale.com>
> > > > > ---
> > > > > drivers/iommu/fsl_pamu.c | 43
> > ++++++++++++++++++++++++++++---
> > > > -----
> > > > > drivers/iommu/fsl_pamu.h | 1 +
> > > > > drivers/iommu/fsl_pamu_domain.c | 46
> > > > ++++++++++++++++++++++++++++++++++++---
> > > > > 3 files changed, 78 insertions(+), 12 deletions(-)
> > > > >
> > > > > diff --git a/drivers/iommu/fsl_pamu.c b/drivers/iommu/fsl_pamu.c
> > > > > index
> > > > > cba0498..fb4a031 100644
> > > > > --- a/drivers/iommu/fsl_pamu.c
> > > > > +++ b/drivers/iommu/fsl_pamu.c
> > > > > @@ -225,6 +225,21 @@ static struct paace *pamu_get_spaace(struct
> > > > > paace *paace,
> > > > > u32 wnum)
> > > > > return spaace;
> > > > > }
> > > > >
> > > > > +/*
> > > > > + * Defaul PPAACE settings for an LIODN.
> > > > > + */
> > > > > +static void setup_default_ppaace(struct paace *ppaace) {
> > > > > + pamu_init_ppaace(ppaace);
> > > > > + /* window size is 2^(WSE+1) bytes */
> > > > > + set_bf(ppaace->addr_bitfields, PPAACE_AF_WSE, 35);
> > > > > + ppaace->wbah = 0;
> > > > > + set_bf(ppaace->addr_bitfields, PPAACE_AF_WBAL, 0);
> > > > > + set_bf(ppaace->impl_attr, PAACE_IA_ATM,
> > > > > + PAACE_ATM_NO_XLATE);
> > > > > + set_bf(ppaace->addr_bitfields, PAACE_AF_AP,
> > > > > + PAACE_AP_PERMS_ALL);
> > > > > +}
> > > > > /**
> > > > > * pamu_get_fspi_and_allocate() - Allocates fspi index and
> > > > > reserves
> > > > subwindows
> > > > > * required for primary PAACE in
> > the
> > > > secondary
> > > > > @@ -253,6 +268,24 @@ static unsigned long
> > > > > pamu_get_fspi_and_allocate(u32
> > > > > subwin_cnt)
> > > > > return (spaace_addr - (unsigned long)spaact) / (sizeof(struct
> > > > > paace)); }
> > > > >
> > > > > +/* Reset the PAACE entry to the default state */ void
> > > > > +enable_default_dma_window(int liodn) {
> > > > > + struct paace *ppaace;
> > > > > +
> > > > > + ppaace = pamu_get_ppaace(liodn);
> > > > > + if (!ppaace) {
> > > > > + pr_debug("Invalid liodn entry\n");
> > > > > + return;
> > > > > + }
> > > > > +
> > > > > + memset(ppaace, 0, sizeof(struct paace));
> > > > > +
> > > > > + setup_default_ppaace(ppaace);
> > > > > + mb();
> > > > > + pamu_enable_liodn(liodn);
> > > > > +}
> > > > > +
> > > > > /* Release the subwindows reserved for a particular LIODN */
> > > > > void pamu_free_subwins(int liodn) { @@ -752,15 +785,7 @@ static
> > > > > void __init
> > > > > setup_liodns(void)
> > > > > continue;
> > > > > }
> > > > > ppaace = pamu_get_ppaace(liodn);
> > > > > - pamu_init_ppaace(ppaace);
> > > > > - /* window size is 2^(WSE+1) bytes */
> > > > > - set_bf(ppaace->addr_bitfields, PPAACE_AF_WSE,
> > 35);
> > > > > - ppaace->wbah = 0;
> > > > > - set_bf(ppaace->addr_bitfields, PPAACE_AF_WBAL,
> > 0);
> > > > > - set_bf(ppaace->impl_attr, PAACE_IA_ATM,
> > > > > - PAACE_ATM_NO_XLATE);
> > > > > - set_bf(ppaace->addr_bitfields, PAACE_AF_AP,
> > > > > - PAACE_AP_PERMS_ALL);
> > > > > + setup_default_ppaace(ppaace);
> > > > > if (of_device_is_compatible(node, "fsl,qman-
> > portal"))
> > > > > setup_qbman_paace(ppaace,
> > QMAN_PORTAL_PAACE);
> > > > > if (of_device_is_compatible(node, "fsl,qman"))
> > diff --
> > > > git
> > > > > a/drivers/iommu/fsl_pamu.h b/drivers/iommu/fsl_pamu.h index
> > > > > 8fc1a12..0edcbbbb
> > > > > 100644
> > > > > --- a/drivers/iommu/fsl_pamu.h
> > > > > +++ b/drivers/iommu/fsl_pamu.h
> > > > > @@ -406,5 +406,6 @@ void get_ome_index(u32 *omi_index, struct
> > > > > device *dev); int pamu_update_paace_stash(int liodn, u32
> > > > > subwin,
> > > > > u32 value); int pamu_disable_spaace(int liodn, u32 subwin);
> > > > > u32 pamu_get_max_subwin_cnt(void);
> > > > > +void enable_default_dma_window(int liodn);
> > > > >
> > > > > #endif /* __FSL_PAMU_H */
> > > > > diff --git a/drivers/iommu/fsl_pamu_domain.c
> > > > > b/drivers/iommu/fsl_pamu_domain.c index 966ae70..dd6cafc 100644
> > > > > --- a/drivers/iommu/fsl_pamu_domain.c
> > > > > +++ b/drivers/iommu/fsl_pamu_domain.c
> > > > > @@ -340,17 +340,57 @@ static inline struct device_domain_info
> > > > > *find_domain(struct device *dev)
> > > > > return dev->archdata.iommu_domain; }
> > > > >
> > > > > +/* Disable device DMA capability and enable default DMA window
> > > > > +*/ static void disable_device_dma(struct device_domain_info *info,
> > > > > + int enable_dma_window)
> > > > > +{
> > > > > +#ifdef CONFIG_PCI
> > > > > + if (info->dev->bus == &pci_bus_type) {
> > > > > + struct pci_dev *pdev = NULL;
> > > > > + pdev = to_pci_dev(info->dev);
> > > > > + if (pci_is_enabled(pdev))
> > > > > + pci_disable_device(pdev);
> > > > > + }
> > > > > +#endif
> > > > > +
> > > > > + if (enable_dma_window)
> > > > > + enable_default_dma_window(info->liodn);
> > > > > +}
> > > > > +
> > > > > +static int check_for_shared_liodn(struct device_domain_info
> > > > > +*info)
> > {
> > > > > + struct device_domain_info *tmp;
> > > > > +
> > > > > + /*
> > > > > + * Sanity check, to ensure that this is not a
> > > > > + * shared LIODN. In case of a PCIe controller
> > > > > + * it's possible that all PCIe devices share
> > > > > + * the same LIODN.
> > > > > + */
> > > > > + list_for_each_entry(tmp, &info->domain->devices, link) {
> > > > > + if (info->liodn == tmp->liodn)
> > > > > + return 1;
> > > > > + }
> > > > > +
> > > > > + return 0;
> > > > > +}
> > > > > +
> > > > > static void remove_device_ref(struct device_domain_info *info,
> > > > > u32
> > > > win_cnt) {
> > > > > unsigned long flags;
> > > > > + int enable_dma_window = 0;
> > > > >
> > > > > list_del(&info->link);
> > > > > spin_lock_irqsave(&iommu_lock, flags);
> > > > > - if (win_cnt > 1)
> > > > > - pamu_free_subwins(info->liodn);
> > > > > - pamu_disable_liodn(info->liodn);
> > > > > + if (!check_for_shared_liodn(info)) {
> > > >
> > > > One query; Do we really need to check for this?
> > > >
> > > [Sethi Varun-B16395] Yes, just a sanity check to ensure that there
> > > are no more devices linked to this LIODN and we can disable it.
> >
> > Varun, trying to understand this; say there are two device under a PCI
> > controller which share the LIODN of PCI controller, So both of the
> > device must be unbound from kernel driver and then bind both to VFIO.
> >
> > Now when guest terminated then remove_device_ref() will be called for
> > both of device but the sanity check will pass for the one which will
> > be called later, is this right?
> >
> Yes, when the first device is detached PAMU LIODN table entry is not disabled.
> The LIODN would only be disabled once all devices are detached.
Ok, thanks for clarification
Patch series looks good to me.
>
> -Varun
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