Re: [Qemu-ppc] [PATCH qemu v17 11/12] spapr_pci/spapr_pci_vfio: Support Dynamic DMA Windows (DDW)

[Alexey Kardashevskiy]

On 08/06/16 15:57, David Gibson wrote:
> On Mon, Jun 06, 2016 at 06:12:58PM +1000, Alexey Kardashevskiy wrote:
>> On 06/06/16 15:57, David Gibson wrote:
>>> On Wed, Jun 01, 2016 at 06:57:42PM +1000, Alexey Kardashevskiy wrote:
>>>> This adds support for Dynamic DMA Windows (DDW) option defined by
>>>> the SPAPR specification which allows to have additional DMA window(s)
>>>>
>>>> The "ddw" property is enabled by default on a PHB but for compatibility
>>>> the pseries-2.5 machine (TODO: update version) and older disable it.
>>>
>>> Looks like your todo is now todone, but you need to update the commit
>>> message.
>>>
>>>> This also creates a single DMA window for the older machines to
>>>> maintain backward migration.
>>>>
>>>> This implements DDW for PHB with emulated and VFIO devices. The host
>>>> kernel support is required. The advertised IOMMU page sizes are 4K and
>>>> 64K; 16M pages are supported but not advertised by default, in order to
>>>> enable them, the user has to specify "pgsz" property for PHB and
>>>> enable huge pages for RAM.
>>>>
>>>> The existing linux guests try creating one additional huge DMA window
>>>> with 64K or 16MB pages and map the entire guest RAM to. If succeeded,
>>>> the guest switches to dma_direct_ops and never calls TCE hypercalls
>>>> (H_PUT_TCE,...) again. This enables VFIO devices to use the entire RAM
>>>> and not waste time on map/unmap later. This adds a "dma64_win_addr"
>>>> property which is a bus address for the 64bit window and by default
>>>> set to 0x800.0000.0000.0000 as this is what the modern POWER8 hardware
>>>> uses and this allows having emulated and VFIO devices on the same bus.
>>>>
>>>> This adds 4 RTAS handlers:
>>>> * ibm,query-pe-dma-window
>>>> * ibm,create-pe-dma-window
>>>> * ibm,remove-pe-dma-window
>>>> * ibm,reset-pe-dma-window
>>>> These are registered from type_init() callback.
>>>>
>>>> These RTAS handlers are implemented in a separate file to avoid polluting
>>>> spapr_iommu.c with PCI.
>>>>
>>>> This changes sPAPRPHBState::dma_liobn to an array to allow 2 LIOBNs.
>>>>
>>>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
>>>
>>> Looks pretty close to ready.
>>>
>>> There are a handful of nits and one real error noted below.
>>>
>>>> ---
>>>> Changes:
>>>> v17:
>>>> * fixed: "query" did return non-page-shifted value when memory hotplug is 
>>>> enabled
>>>>
>>>> v16:
>>>> * s/dma_liobn/dma_liobn[SPAPR_PCI_DMA_MAX_WINDOWS]/
>>>> * s/SPAPR_PCI_LIOBN()/dma_liobn[]/
>>>>
>>>> v15:
>>>> * moved page mask filtering to PHB realize(), use "-mempath" to know
>>>> if there are huge pages
>>>> * fixed error reporting in RTAS handlers
>>>> * max window size accounts now hotpluggable memory boundaries
>>>> ---
>>>>  hw/ppc/Makefile.objs        |   1 +
>>>>  hw/ppc/spapr.c              |   5 +
>>>>  hw/ppc/spapr_pci.c          |  77 +++++++++---
>>>>  hw/ppc/spapr_rtas_ddw.c     | 293 
>>>> ++++++++++++++++++++++++++++++++++++++++++++
>>>>  include/hw/pci-host/spapr.h |   8 +-
>>>>  include/hw/ppc/spapr.h      |  16 ++-
>>>>  trace-events                |   4 +
>>>>  7 files changed, 383 insertions(+), 21 deletions(-)
>>>>  create mode 100644 hw/ppc/spapr_rtas_ddw.c
>>>>
>>>> diff --git a/hw/ppc/Makefile.objs b/hw/ppc/Makefile.objs
>>>> index c1ffc77..986b36f 100644
>>>> --- a/hw/ppc/Makefile.objs
>>>> +++ b/hw/ppc/Makefile.objs
>>>> @@ -7,6 +7,7 @@ obj-$(CONFIG_PSERIES) += spapr_pci.o spapr_rtc.o 
>>>> spapr_drc.o spapr_rng.o
>>>>  ifeq ($(CONFIG_PCI)$(CONFIG_PSERIES)$(CONFIG_LINUX), yyy)
>>>>  obj-y += spapr_pci_vfio.o
>>>>  endif
>>>> +obj-$(CONFIG_PSERIES) += spapr_rtas_ddw.o
>>>>  # PowerPC 4xx boards
>>>>  obj-y += ppc405_boards.o ppc4xx_devs.o ppc405_uc.o ppc440_bamboo.o
>>>>  obj-y += ppc4xx_pci.o
>>>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>>>> index 44e401a..6ddcda9 100644
>>>> --- a/hw/ppc/spapr.c
>>>> +++ b/hw/ppc/spapr.c
>>>> @@ -2366,6 +2366,11 @@ DEFINE_SPAPR_MACHINE(2_6, "2.6", true);
>>>>          .driver   = "spapr-vlan", \
>>>>          .property = "use-rx-buffer-pools", \
>>>>          .value    = "off", \
>>>> +    }, \
>>>> +    {\
>>>> +        .driver   = TYPE_SPAPR_PCI_HOST_BRIDGE,\
>>>> +        .property = "ddw",\
>>>> +        .value    = stringify(off),\
>>>>      },
>>>>  
>>>>  static void spapr_machine_2_5_instance_options(MachineState *machine)
>>>> diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
>>>> index 68de523..bcf0360 100644
>>>> --- a/hw/ppc/spapr_pci.c
>>>> +++ b/hw/ppc/spapr_pci.c
>>>> @@ -35,6 +35,7 @@
>>>>  #include "hw/ppc/spapr.h"
>>>>  #include "hw/pci-host/spapr.h"
>>>>  #include "exec/address-spaces.h"
>>>> +#include "exec/ram_addr.h"
>>>>  #include <libfdt.h>
>>>>  #include "trace.h"
>>>>  #include "qemu/error-report.h"
>>>> @@ -45,6 +46,7 @@
>>>>  #include "hw/ppc/spapr_drc.h"
>>>>  #include "sysemu/device_tree.h"
>>>>  #include "sysemu/kvm.h"
>>>> +#include "sysemu/hostmem.h"
>>>>  
>>>>  #include "hw/vfio/vfio.h"
>>>>  
>>>> @@ -1088,7 +1090,7 @@ static void 
>>>> spapr_phb_add_pci_device(sPAPRDRConnector *drc,
>>>>      int fdt_start_offset = 0, fdt_size;
>>>>  
>>>>      if (object_dynamic_cast(OBJECT(pdev), "vfio-pci")) {
>>>> -        sPAPRTCETable *tcet = spapr_tce_find_by_liobn(phb->dma_liobn);
>>>> +        sPAPRTCETable *tcet = spapr_tce_find_by_liobn(phb->dma_liobn[0]);
>>>>  
>>>>          spapr_tce_set_need_vfio(tcet, true);
>>>>      }
>>>
>>> Hang on.. I thought you'd got rid of the need for this explicit
>>> set_need_vfio() stuff.
>>
>>
>> It is in 12/12 (which I'll split in 2 halves when I respin this), I moved
>> it to the end as it is not essential for DDW itself.
> 
> Yes, sorry, I saw that shortly after writing this.
> 
>>>> @@ -1310,11 +1312,14 @@ static void spapr_phb_realize(DeviceState *dev, 
>>>> Error **errp)
>>>>      PCIBus *bus;
>>>>      uint64_t msi_window_size = 4096;
>>>>      sPAPRTCETable *tcet;
>>>> +    const unsigned windows_supported =
>>>> +        sphb->ddw_enabled ? SPAPR_PCI_DMA_MAX_WINDOWS : 1;
>>>>  
>>>>      if (sphb->index != (uint32_t)-1) {
>>>>          hwaddr windows_base;
>>>>  
>>>> -        if ((sphb->buid != (uint64_t)-1) || (sphb->dma_liobn != 
>>>> (uint32_t)-1)
>>>> +        if ((sphb->buid != (uint64_t)-1) || (sphb->dma_liobn[0] != 
>>>> (uint32_t)-1)
>>>> +            || ((sphb->dma_liobn[1] != (uint32_t)-1) && 
>>>> (windows_supported > 1))
>>>>              || (sphb->mem_win_addr != (hwaddr)-1)
>>>>              || (sphb->io_win_addr != (hwaddr)-1)) {
>>>>              error_setg(errp, "Either \"index\" or other parameters must"
>>>> @@ -1329,7 +1334,9 @@ static void spapr_phb_realize(DeviceState *dev, 
>>>> Error **errp)
>>>>          }
>>>>  
>>>>          sphb->buid = SPAPR_PCI_BASE_BUID + sphb->index;
>>>> -        sphb->dma_liobn = SPAPR_PCI_LIOBN(sphb->index, 0);
>>>> +        for (i = 0; i < windows_supported; ++i) {
>>>> +            sphb->dma_liobn[i] = SPAPR_PCI_LIOBN(sphb->index, i);
>>>> +        }
>>>>  
>>>>          windows_base = SPAPR_PCI_WINDOW_BASE
>>>>              + sphb->index * SPAPR_PCI_WINDOW_SPACING;
>>>> @@ -1342,8 +1349,9 @@ static void spapr_phb_realize(DeviceState *dev, 
>>>> Error **errp)
>>>>          return;
>>>>      }
>>>>  
>>>> -    if (sphb->dma_liobn == (uint32_t)-1) {
>>>> -        error_setg(errp, "LIOBN not specified for PHB");
>>>> +    if ((sphb->dma_liobn[0] == (uint32_t)-1) ||
>>>> +        ((sphb->dma_liobn[1] == (uint32_t)-1) && (windows_supported > 
>>>> 1))) {
>>>> +        error_setg(errp, "LIOBN(s) not specified for PHB");
>>>>          return;
>>>>      }
>>>
>>> Hrm.. there's a bit of false generality here, since this would break
>>> if windows_supported > 2, and dma_liobn[2] was not specified.  Not
>>> urgent for the initial commit though.
>>
>>
>> Is s/windows_supported > 1/windows_supported == 2/ any better here?
> 
> Not really.  Unless you also have a windows_supported > 2 case (which
> could just error / abort / whatever).


It cannot be >2 as SPAPR_PCI_DMA_MAX_WINDOWS is defined as "2" now and it
is quite unlikely to change in the future.

What do I do right now? :)


-- 
Alexey

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