Messages in this thread | | | Date | Fri, 17 Apr 2015 20:09:29 +1000 | From | Alexey Kardashevskiy <> | Subject | Re: [PATCH kernel v8 14/31] vfio: powerpc/spapr: powerpc/powernv/ioda2: Rework IOMMU ownership control |
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On 04/16/2015 04:07 PM, David Gibson wrote: > On Fri, Apr 10, 2015 at 04:30:56PM +1000, Alexey Kardashevskiy wrote: >> At the moment the iommu_table struct has a set_bypass() which enables/ >> disables DMA bypass on IODA2 PHB. This is exposed to POWERPC IOMMU code >> which calls this callback when external IOMMU users such as VFIO are >> about to get over a PHB. >> >> The set_bypass() callback is not really an iommu_table function but >> IOMMU/PE function. This introduces a iommu_table_group_ops struct and >> adds a set_ownership() callback to it which is called when an external >> user takes control over the IOMMU. > > Do you really need separate ops structures at both the single table > and table group level? The different tables in a group will all > belong to the same basic iommu won't they?
IOMMU tables exist alone in VIO. Also, the platform code uses just a table (or it is in bypass mode) and does not care about table groups. It looked more clean for myself to keep them separated. Should I still merge those?
> >> This renames set_bypass() to set_ownership() as it is not necessarily >> just enabling bypassing, it can be something else/more so let's give it >> more generic name. The bool parameter is inverted. >> >> The callback is implemented for IODA2 only. Other platforms (P5IOC2, >> IODA1) will use the old iommu_take_ownership/iommu_release_ownership API. >> >> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> >> --- >> arch/powerpc/include/asm/iommu.h | 14 +++++++++++++- >> arch/powerpc/platforms/powernv/pci-ioda.c | 30 ++++++++++++++++++++++-------- >> drivers/vfio/vfio_iommu_spapr_tce.c | 25 +++++++++++++++++++++---- >> 3 files changed, 56 insertions(+), 13 deletions(-) >> >> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h >> index b9e50d3..d1f8c6c 100644 >> --- a/arch/powerpc/include/asm/iommu.h >> +++ b/arch/powerpc/include/asm/iommu.h >> @@ -92,7 +92,6 @@ struct iommu_table { >> unsigned long it_page_shift;/* table iommu page size */ >> struct iommu_table_group *it_group; >> struct iommu_table_ops *it_ops; >> - void (*set_bypass)(struct iommu_table *tbl, bool enable); >> }; >> >> /* Pure 2^n version of get_order */ >> @@ -127,11 +126,24 @@ extern struct iommu_table *iommu_init_table(struct iommu_table * tbl, >> >> #define IOMMU_TABLE_GROUP_MAX_TABLES 1 >> >> +struct iommu_table_group; >> + >> +struct iommu_table_group_ops { >> + /* >> + * Switches ownership from the kernel itself to an external >> + * user. While onwership is enabled, the kernel cannot use IOMMU >> + * for itself. >> + */ >> + void (*set_ownership)(struct iommu_table_group *table_group, >> + bool enable); > > The meaning of "enable" in a function called "set_ownership" is > entirely obscure.
Suggest something better please :) I have nothing better...
> >> +}; >> + >> struct iommu_table_group { >> #ifdef CONFIG_IOMMU_API >> struct iommu_group *group; >> #endif >> struct iommu_table tables[IOMMU_TABLE_GROUP_MAX_TABLES]; >> + struct iommu_table_group_ops *ops; >> }; >> >> #ifdef CONFIG_IOMMU_API >> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c >> index a964c50..9687731 100644 >> --- a/arch/powerpc/platforms/powernv/pci-ioda.c >> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c >> @@ -1255,10 +1255,8 @@ static void pnv_pci_ioda_setup_dma_pe(struct pnv_phb *phb, >> __free_pages(tce_mem, get_order(TCE32_TABLE_SIZE * segs)); >> } >> >> -static void pnv_pci_ioda2_set_bypass(struct iommu_table *tbl, bool enable) >> +static void pnv_pci_ioda2_set_bypass(struct pnv_ioda_pe *pe, bool enable) >> { >> - struct pnv_ioda_pe *pe = container_of(tbl->it_group, struct pnv_ioda_pe, >> - table_group); >> uint16_t window_id = (pe->pe_number << 1 ) + 1; >> int64_t rc; >> >> @@ -1286,7 +1284,8 @@ static void pnv_pci_ioda2_set_bypass(struct iommu_table *tbl, bool enable) >> * host side. >> */ >> if (pe->pdev) >> - set_iommu_table_base(&pe->pdev->dev, tbl); >> + set_iommu_table_base(&pe->pdev->dev, >> + &pe->table_group.tables[0]); >> else >> pnv_ioda_setup_bus_dma(pe, pe->pbus, false); >> } >> @@ -1302,13 +1301,27 @@ static void pnv_pci_ioda2_setup_bypass_pe(struct pnv_phb *phb, >> /* TVE #1 is selected by PCI address bit 59 */ >> pe->tce_bypass_base = 1ull << 59; >> >> - /* Install set_bypass callback for VFIO */ >> - pe->table_group.tables[0].set_bypass = pnv_pci_ioda2_set_bypass; >> - >> /* Enable bypass by default */ >> - pnv_pci_ioda2_set_bypass(&pe->table_group.tables[0], true); >> + pnv_pci_ioda2_set_bypass(pe, true); >> } >> >> +static void pnv_ioda2_set_ownership(struct iommu_table_group *table_group, >> + bool enable) >> +{ >> + struct pnv_ioda_pe *pe = container_of(table_group, struct pnv_ioda_pe, >> + table_group); >> + if (enable) >> + iommu_take_ownership(table_group); >> + else >> + iommu_release_ownership(table_group); >> + >> + pnv_pci_ioda2_set_bypass(pe, !enable); >> +} >> + >> +static struct iommu_table_group_ops pnv_pci_ioda2_ops = { >> + .set_ownership = pnv_ioda2_set_ownership, >> +}; >> + >> static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb, >> struct pnv_ioda_pe *pe) >> { >> @@ -1376,6 +1389,7 @@ static void pnv_pci_ioda2_setup_dma_pe(struct pnv_phb *phb, >> } >> tbl->it_ops = &pnv_iommu_ops; >> iommu_init_table(tbl, phb->hose->node); >> + pe->table_group.ops = &pnv_pci_ioda2_ops; >> iommu_register_group(&pe->table_group, phb->hose->global_number, >> pe->pe_number); >> >> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c >> index 9f38351..d5d8c50 100644 >> --- a/drivers/vfio/vfio_iommu_spapr_tce.c >> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c >> @@ -535,9 +535,22 @@ static int tce_iommu_attach_group(void *iommu_data, >> goto unlock_exit; >> } >> >> - ret = iommu_take_ownership(table_group); >> - if (!ret) >> - container->grp = iommu_group; >> + if (!table_group->ops || !table_group->ops->set_ownership) { >> + ret = iommu_take_ownership(table_group); >> + } else { >> + /* >> + * Disable iommu bypass, otherwise the user can DMA to all of >> + * our physical memory via the bypass window instead of just >> + * the pages that has been explicitly mapped into the iommu >> + */ >> + table_group->ops->set_ownership(table_group, true); > > And here to disable bypass you call it with enable=true, so it doesn't > even have the same meaning as it used to.
I do not disable bypass per se (even if it what set_ownership(true) does) as it is IODA business and VFIO has no idea about it. I do take control over the group. I am not following you here - what used to have the same meaning?
> > Plus, you should fold the logic to call the callback if necessary into > iommu_take_ownership().
I really want to keep VFIO stuff out of arch/powerpc/kernel/iommu.c as much as possible as it is for platform DMA/IOMMU, not VFIO (which got SPAPR driver for that). ops->set_ownership() is one of these things.
iommu_take_ownership()/iommu_release_ownership() are helpers for old-style commercially-unsupported P5IOC2/IODA1, and this is kind of a hack while ops->set_ownership() is an interface for VFIO to do dynamic windows thing.
If it makes sense, I could fold the previous patch into this one and move iommu_take_ownership()/iommu_release_ownership() to vfio_iommu_spapr_tce.c, should I? Or leave things are they are now.
>> + ret = 0; >> + } >> + >> + if (ret) >> + goto unlock_exit; >> + >> + container->grp = iommu_group; >> >> unlock_exit: >> mutex_unlock(&container->lock); >> @@ -572,7 +585,11 @@ static void tce_iommu_detach_group(void *iommu_data, >> table_group = iommu_group_get_iommudata(iommu_group); >> BUG_ON(!table_group); >> >> - iommu_release_ownership(table_group); >> + /* Kernel owns the device now, we can restore bypass */ >> + if (!table_group->ops || !table_group->ops->set_ownership) >> + iommu_release_ownership(table_group); >> + else >> + table_group->ops->set_ownership(table_group, false); > > Likewise fold this if into iommu_release_ownership(). > >> unlock_exit: >> mutex_unlock(&container->lock); >
-- Alexey
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