Re: [Qemu-devel] [PULL 15/16] spapr_pci: Add a 64-bit MMIO window

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, Nov 04, 2016 at 04:03:31PM +1100, Alexey Kardashevskiy wrote:
> On 17/10/16 13:43, David Gibson wrote:
> > On real hardware, and under pHyp, the PCI host bridges on Power machines
> > typically advertise two outbound MMIO windows from the guest's physical
> > memory space to PCI memory space:
> >   - A 32-bit window which maps onto 2GiB..4GiB in the PCI address space
> >   - A 64-bit window which maps onto a large region somewhere high in PCI
> >     address space (traditionally this used an identity mapping from guest
> >     physical address to PCI address, but that's not always the case)
> > 
> > The qemu implementation in spapr-pci-host-bridge, however, only supports a
> > single outbound MMIO window, however.  At least some Linux versions expect
> > the two windows however, so we arranged this window to map onto the PCI
> > memory space from 2 GiB..~64 GiB, then advertised it as two contiguous
> > windows, the "32-bit" window from 2G..4G and the "64-bit" window from
> > 4G..~64G.
> > 
> > This approach means, however, that the 64G window is not naturally aligned.
> > In turn this limits the size of the largest BAR we can map (which does have
> > to be naturally aligned) to roughly half of the total window.  With some
> > large nVidia GPGPU cards which have huge memory BARs, this is starting to
> > be a problem.
> > 
> > This patch adds true support for separate 32-bit and 64-bit outbound MMIO
> > windows to the spapr-pci-host-bridge implementation, each of which can
> > be independently configured.  The 32-bit window always maps to 2G.. in PCI
> > space, but the PCI address of the 64-bit window can be configured (it
> > defaults to the same as the guest physical address).
> > 
> > So as not to break possible existing configurations, as long as a 64-bit
> > window is not specified, a large single window can be specified.  This
> > will appear the same way to the guest as the old approach, although it's
> > now implemented by two contiguous memory regions rather than a single one.
> > 
> > For now, this only adds the possibility of 64-bit windows.  The default
> > configuration still uses the legacy mode.
> 
> 
> This breaks migration to QEMU v2.7, the destination reports:
> 
> 22901@1478235261.799031:vmstate_load spapr_pci, spapr_pci
> 22901@1478235261.799040:vmstate_load_field_error field "mem_win_size" load
> failed, ret = -22
> qemu-hostos1: error while loading state for instance 0x0 of device 'spapr_pci'
> 22901@1478235261.801324:migrate_set_state new state 7
> qemu-hostos1: load of migration failed: Invalid argument
> 
> 
> mem_win_size decreased from 0xf80000000 to 0x80000000.
> 
> I'd think it should be allowed to migrate like this.

AIUI, we don't generally care (upstream) about migration from newer to
older qemu, only from older to newer.  Trying to maintain backwards
migration makes it almost impossible to fix anything at all, ever.

> 
> 
> The source PHB is:
> 
> (qemu) info qtree
> bus: main-system-bus
>   type System
>   dev: spapr-pci-host-bridge, id ""
>     index = 0 (0x0)
>     buid = 576460752840294400 (0x800000020000000)
>     liobn = 2147483648 (0x80000000)
>     liobn64 = 4294967295 (0xffffffff)
>     mem_win_addr = 1102195982336 (0x100a0000000)
>     mem_win_size = 2147483648 (0x80000000)
>     mem64_win_addr = 1104343465984 (0x10120000000)
>     mem64_win_size = 64424509440 (0xf00000000)
>     mem64_win_pciaddr = 4294967296 (0x100000000)
> 
> 
> The destination PHB is:
> 
> (qemu) info qtree
> bus: main-system-bus
>   type System
>   dev: spapr-pci-host-bridge, id ""
>     index = 0 (0x0)
>     buid = 576460752840294400 (0x800000020000000)
>     liobn = 2147483648 (0x80000000)
>     liobn64 = 4294967295 (0xffffffff)
>     mem_win_addr = 1102195982336 (0x100a0000000)
>     mem_win_size = 66571993088 (0xf80000000)
> 
> 
> 
> The source QEMU cmdline:
> 
> /home/aik/p/qemu/ppc64-softmmu/qemu-system-ppc64 -nodefaults \
> -chardev stdio,id=STDIO0,signal=off,mux=on \
> -device spapr-vty,id=svty0,chardev=STDIO0,reg=0x71000100 \
> -mon id=MON0,chardev=STDIO0,mode=readline -nographic -vga none \
> -kernel /home/aik/t/vml450le \
> -initrd /home/aik/t/le.cpio -m 4G \
> -machine pseries-2.6 -enable-kvm \
> 
> 
> The destination (./qemu-hostos1 is v2.7.0 from
> https://github.com/open-power-host-os/qemu/commits/hostos-stable )
> 
> ./qemu-hostos1 -nodefaults \
> -chardev stdio,id=STDIO0,signal=off,mux=on \
> -device spapr-vty,id=svty0,chardev=STDIO0,reg=0x71000100 \
> -mon id=MON0,chardev=STDIO0,mode=readline -nographic -vga none -m 4G \
> -machine pseries-2.6 -enable-kvm \
> -mon chardev=SOCKET0,mode=readline -incoming "tcp:fstn1:22222"
> 
> 
> 
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > Reviewed-by: Laurent Vivier <lvivier@redhat.com>
> > ---
> >  hw/ppc/spapr.c              | 10 +++++--
> >  hw/ppc/spapr_pci.c          | 70 ++++++++++++++++++++++++++++++++++++---------
> >  include/hw/pci-host/spapr.h |  8 ++++--
> >  include/hw/ppc/spapr.h      |  3 +-
> >  4 files changed, 72 insertions(+), 19 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index d747e58..ea5d0e6 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -2371,7 +2371,8 @@ static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
> >  }
> >  
> >  static void spapr_phb_placement(sPAPRMachineState *spapr, uint32_t index,
> > -                                uint64_t *buid, hwaddr *pio, hwaddr *mmio,
> > +                                uint64_t *buid, hwaddr *pio,
> > +                                hwaddr *mmio32, hwaddr *mmio64,
> >                                  unsigned n_dma, uint32_t *liobns, Error **errp)
> >  {
> >      const uint64_t base_buid = 0x800000020000000ULL;
> > @@ -2409,7 +2410,12 @@ static void spapr_phb_placement(sPAPRMachineState *spapr, uint32_t index,
> >  
> >      phb_base = phb0_base + index * phb_spacing;
> >      *pio = phb_base + pio_offset;
> > -    *mmio = phb_base + mmio_offset;
> > +    *mmio32 = phb_base + mmio_offset;
> > +    /*
> > +     * We don't set the 64-bit MMIO window, relying on the PHB's
> > +     * fallback behaviour of automatically splitting a large "32-bit"
> > +     * window into contiguous 32-bit and 64-bit windows
> > +     */
> >  }
> >  
> >  static void spapr_machine_class_init(ObjectClass *oc, void *data)
> > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> > index 8bd7f59..10d5de2 100644
> > --- a/hw/ppc/spapr_pci.c
> > +++ b/hw/ppc/spapr_pci.c
> > @@ -1317,14 +1317,16 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
> >          if ((sphb->buid != (uint64_t)-1) || (sphb->dma_liobn[0] != (uint32_t)-1)
> >              || (sphb->dma_liobn[1] != (uint32_t)-1 && windows_supported == 2)
> >              || (sphb->mem_win_addr != (hwaddr)-1)
> > +            || (sphb->mem64_win_addr != (hwaddr)-1)
> >              || (sphb->io_win_addr != (hwaddr)-1)) {
> >              error_setg(errp, "Either \"index\" or other parameters must"
> >                         " be specified for PAPR PHB, not both");
> >              return;
> >          }
> >  
> > -        smc->phb_placement(spapr, sphb->index, &sphb->buid,
> > -                           &sphb->io_win_addr, &sphb->mem_win_addr,
> > +        smc->phb_placement(spapr, sphb->index,
> > +                           &sphb->buid, &sphb->io_win_addr,
> > +                           &sphb->mem_win_addr, &sphb->mem64_win_addr,
> >                             windows_supported, sphb->dma_liobn, &local_err);
> >          if (local_err) {
> >              error_propagate(errp, local_err);
> > @@ -1353,6 +1355,38 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
> >          return;
> >      }
> >  
> > +    if (sphb->mem64_win_size != 0) {
> > +        if (sphb->mem64_win_addr == (hwaddr)-1) {
> > +            error_setg(errp,
> > +                       "64-bit memory window address not specified for PHB");
> > +            return;
> > +        }
> > +
> > +        if (sphb->mem_win_size > SPAPR_PCI_MEM32_WIN_SIZE) {
> > +            error_setg(errp, "32-bit memory window of size 0x%"HWADDR_PRIx
> > +                       " (max 2 GiB)", sphb->mem_win_size);
> > +            return;
> > +        }
> > +
> > +        if (sphb->mem64_win_pciaddr == (hwaddr)-1) {
> > +            /* 64-bit window defaults to identity mapping */
> > +            sphb->mem64_win_pciaddr = sphb->mem64_win_addr;
> > +        }
> > +    } else if (sphb->mem_win_size > SPAPR_PCI_MEM32_WIN_SIZE) {
> > +        /*
> > +         * For compatibility with old configuration, if no 64-bit MMIO
> > +         * window is specified, but the ordinary (32-bit) memory
> > +         * window is specified as > 2GiB, we treat it as a 2GiB 32-bit
> > +         * window, with a 64-bit MMIO window following on immediately
> > +         * afterwards
> > +         */
> > +        sphb->mem64_win_size = sphb->mem_win_size - SPAPR_PCI_MEM32_WIN_SIZE;
> > +        sphb->mem64_win_addr = sphb->mem_win_addr + SPAPR_PCI_MEM32_WIN_SIZE;
> > +        sphb->mem64_win_pciaddr =
> > +            SPAPR_PCI_MEM_WIN_BUS_OFFSET + SPAPR_PCI_MEM32_WIN_SIZE;
> > +        sphb->mem_win_size = SPAPR_PCI_MEM32_WIN_SIZE;
> > +    }
> > +
> >      if (spapr_pci_find_phb(spapr, sphb->buid)) {
> >          error_setg(errp, "PCI host bridges must have unique BUIDs");
> >          return;
> > @@ -1366,12 +1400,19 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
> >      sprintf(namebuf, "%s.mmio", sphb->dtbusname);
> >      memory_region_init(&sphb->memspace, OBJECT(sphb), namebuf, UINT64_MAX);
> >  
> > -    sprintf(namebuf, "%s.mmio-alias", sphb->dtbusname);
> > -    memory_region_init_alias(&sphb->memwindow, OBJECT(sphb),
> > +    sprintf(namebuf, "%s.mmio32-alias", sphb->dtbusname);
> > +    memory_region_init_alias(&sphb->mem32window, OBJECT(sphb),
> >                               namebuf, &sphb->memspace,
> >                               SPAPR_PCI_MEM_WIN_BUS_OFFSET, sphb->mem_win_size);
> >      memory_region_add_subregion(get_system_memory(), sphb->mem_win_addr,
> > -                                &sphb->memwindow);
> > +                                &sphb->mem32window);
> > +
> > +    sprintf(namebuf, "%s.mmio64-alias", sphb->dtbusname);
> > +    memory_region_init_alias(&sphb->mem64window, OBJECT(sphb),
> > +                             namebuf, &sphb->memspace,
> > +                             sphb->mem64_win_pciaddr, sphb->mem64_win_size);
> > +    memory_region_add_subregion(get_system_memory(), sphb->mem64_win_addr,
> > +                                &sphb->mem64window);
> >  
> >      /* Initialize IO regions */
> >      sprintf(namebuf, "%s.io", sphb->dtbusname);
> > @@ -1524,6 +1565,10 @@ static Property spapr_phb_properties[] = {
> >      DEFINE_PROP_UINT64("mem_win_addr", sPAPRPHBState, mem_win_addr, -1),
> >      DEFINE_PROP_UINT64("mem_win_size", sPAPRPHBState, mem_win_size,
> >                         SPAPR_PCI_MMIO_WIN_SIZE),
> > +    DEFINE_PROP_UINT64("mem64_win_addr", sPAPRPHBState, mem64_win_addr, -1),
> > +    DEFINE_PROP_UINT64("mem64_win_size", sPAPRPHBState, mem64_win_size, 0),
> > +    DEFINE_PROP_UINT64("mem64_win_pciaddr", sPAPRPHBState, mem64_win_pciaddr,
> > +                       -1),
> >      DEFINE_PROP_UINT64("io_win_addr", sPAPRPHBState, io_win_addr, -1),
> >      DEFINE_PROP_UINT64("io_win_size", sPAPRPHBState, io_win_size,
> >                         SPAPR_PCI_IO_WIN_SIZE),
> > @@ -1759,10 +1804,6 @@ int spapr_populate_pci_dt(sPAPRPHBState *phb,
> >      int bus_off, i, j, ret;
> >      char nodename[FDT_NAME_MAX];
> >      uint32_t bus_range[] = { cpu_to_be32(0), cpu_to_be32(0xff) };
> > -    const uint64_t mmiosize = memory_region_size(&phb->memwindow);
> > -    const uint64_t w32max = (1ULL << 32) - SPAPR_PCI_MEM_WIN_BUS_OFFSET;
> > -    const uint64_t w32size = MIN(w32max, mmiosize);
> > -    const uint64_t w64size = (mmiosize > w32size) ? (mmiosize - w32size) : 0;
> >      struct {
> >          uint32_t hi;
> >          uint64_t child;
> > @@ -1777,15 +1818,16 @@ int spapr_populate_pci_dt(sPAPRPHBState *phb,
> >          {
> >              cpu_to_be32(b_ss(2)), cpu_to_be64(SPAPR_PCI_MEM_WIN_BUS_OFFSET),
> >              cpu_to_be64(phb->mem_win_addr),
> > -            cpu_to_be64(w32size),
> > +            cpu_to_be64(phb->mem_win_size),
> >          },
> >          {
> > -            cpu_to_be32(b_ss(3)), cpu_to_be64(1ULL << 32),
> > -            cpu_to_be64(phb->mem_win_addr + w32size),
> > -            cpu_to_be64(w64size)
> > +            cpu_to_be32(b_ss(3)), cpu_to_be64(phb->mem64_win_pciaddr),
> > +            cpu_to_be64(phb->mem64_win_addr),
> > +            cpu_to_be64(phb->mem64_win_size),
> >          },
> >      };
> > -    const unsigned sizeof_ranges = (w64size ? 3 : 2) * sizeof(ranges[0]);
> > +    const unsigned sizeof_ranges =
> > +        (phb->mem64_win_size ? 3 : 2) * sizeof(ranges[0]);
> >      uint64_t bus_reg[] = { cpu_to_be64(phb->buid), 0 };
> >      uint32_t interrupt_map_mask[] = {
> >          cpu_to_be32(b_ddddd(-1)|b_fff(0)), 0x0, 0x0, cpu_to_be32(-1)};
> > diff --git a/include/hw/pci-host/spapr.h b/include/hw/pci-host/spapr.h
> > index 8c9ebfd..23dfb09 100644
> > --- a/include/hw/pci-host/spapr.h
> > +++ b/include/hw/pci-host/spapr.h
> > @@ -53,8 +53,10 @@ struct sPAPRPHBState {
> >      bool dr_enabled;
> >  
> >      MemoryRegion memspace, iospace;
> > -    hwaddr mem_win_addr, mem_win_size, io_win_addr, io_win_size;
> > -    MemoryRegion memwindow, iowindow, msiwindow;
> > +    hwaddr mem_win_addr, mem_win_size, mem64_win_addr, mem64_win_size;
> > +    uint64_t mem64_win_pciaddr;
> > +    hwaddr io_win_addr, io_win_size;
> > +    MemoryRegion mem32window, mem64window, iowindow, msiwindow;
> >  
> >      uint32_t dma_liobn[SPAPR_PCI_DMA_MAX_WINDOWS];
> >      hwaddr dma_win_addr, dma_win_size;
> > @@ -80,6 +82,8 @@ struct sPAPRPHBState {
> >  };
> >  
> >  #define SPAPR_PCI_MEM_WIN_BUS_OFFSET 0x80000000ULL
> > +#define SPAPR_PCI_MEM32_WIN_SIZE     \
> > +    ((1ULL << 32) - SPAPR_PCI_MEM_WIN_BUS_OFFSET)
> >  
> >  #define SPAPR_PCI_MMIO_WIN_SIZE      0xf80000000
> >  #define SPAPR_PCI_IO_WIN_SIZE        0x10000
> > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > index a05783c..aeaba3e 100644
> > --- a/include/hw/ppc/spapr.h
> > +++ b/include/hw/ppc/spapr.h
> > @@ -41,7 +41,8 @@ struct sPAPRMachineClass {
> >      bool use_ohci_by_default;  /* use USB-OHCI instead of XHCI */
> >      const char *tcg_default_cpu; /* which (TCG) CPU to simulate by default */
> >      void (*phb_placement)(sPAPRMachineState *spapr, uint32_t index,
> > -                          uint64_t *buid, hwaddr *pio, hwaddr *mmio,
> > +                          uint64_t *buid, hwaddr *pio, 
> > +                          hwaddr *mmio32, hwaddr *mmio64,
> >                            unsigned n_dma, uint32_t *liobns, Error **errp);
> >  };
> >  
> > 
> 
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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