Re: [Qemu-devel] [PATCH v3 23/23] pci: honor PCI_COMMAND_MASTER

[liu ping fan]

On Wed, Oct 10, 2012 at 12:32 AM, Avi Kivity <address@hidden> wrote:
> Currently we ignore PCI_COMMAND_MASTER completely: DMA succeeds even when
> the bit is clear.
>
> Honor PCI_COMMAND_MASTER by inserting a memory region into the device's
> bus master address space, and tying its enable status to PCI_COMMAND_MASTER.
>
> Tested using
>
>   setpci -s 03 COMMAND=3
>
> while a ping was running on a NIC in slot 3.  The kernel (Linux) detected
> the stall and recovered after the command
>
>   setpci -s 03 COMMAND=7
>
> was issued.
>
> Signed-off-by: Avi Kivity <address@hidden>
> ---
>  hw/pci.c | 13 +++++++++++--
>  hw/pci.h |  1 +
>  2 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/hw/pci.c b/hw/pci.c
> index 8e8e030..7adf61b 100644
> --- a/hw/pci.c
> +++ b/hw/pci.c
> @@ -782,7 +782,11 @@ static PCIDevice *do_pci_register_device(PCIDevice 
> *pci_dev, PCIBus *bus,
>          /* FIXME: Make dma_context_fn use MemoryRegions instead, so this 
> path is
>           * taken unconditionally */
>          /* FIXME: inherit memory region from bus creator */
> -        address_space_init(&pci_dev->bus_master_as, get_system_memory());
> +        memory_region_init_alias(&pci_dev->bus_master_enable_region, "bus 
> master",
> +                                 get_system_memory(), 0,
> +                                 memory_region_size(get_system_memory()));

Could we achieve that  hiding special mr from some address space?  I
think one approach is to limit the iommu's lookup table, but that is
the guest's willing.  The other one is use dummy-mr to overlap some
piece of region of system_memory.
This method will require changing the render sequence of alias mr.

diff --git a/memory.c b/memory.c
index 2f68d67..cf67c66 100644
--- a/memory.c
+++ b/memory.c
@@ -499,6 +499,11 @@ static void render_memory_region(FlatView *view,

     clip = addrrange_intersection(tmp, clip);

+    /* Render subregions in priority order. */
+    QTAILQ_FOREACH(subregion, &mr->subregions, subregions_link) {
+        render_memory_region(view, subregion, base, clip, readonly);
+    }
+
     if (mr->alias) {
         int128_subfrom(&base, int128_make64(mr->alias->addr));
         int128_subfrom(&base, int128_make64(mr->alias_offset));
@@ -506,11 +511,6 @@ static void render_memory_region(FlatView *view,
         return;
     }

-    /* Render subregions in priority order. */
-    QTAILQ_FOREACH(subregion, &mr->subregions, subregions_link) {
-        render_memory_region(view, subregion, base, clip, readonly);
-    }
-

Regards,
pingfan

> +        memory_region_set_enabled(&pci_dev->bus_master_enable_region, false);
> +        address_space_init(&pci_dev->bus_master_as, 
> &pci_dev->bus_master_enable_region);
>          pci_dev->dma = g_new(DMAContext, 1);
>          dma_context_init(pci_dev->dma, &pci_dev->bus_master_as, NULL, NULL, 
> NULL);
>      }
> @@ -841,6 +845,7 @@ static void do_pci_unregister_device(PCIDevice *pci_dev)
>
>      if (!pci_dev->bus->dma_context_fn) {
>          address_space_destroy(&pci_dev->bus_master_as);
> +        memory_region_destroy(&pci_dev->bus_master_enable_region);
>          g_free(pci_dev->dma);
>          pci_dev->dma = NULL;
>      }
> @@ -1065,8 +1070,12 @@ void pci_default_write_config(PCIDevice *d, uint32_t 
> addr, uint32_t val, int l)
>          range_covers_byte(addr, l, PCI_COMMAND))
>          pci_update_mappings(d);
>
> -    if (range_covers_byte(addr, l, PCI_COMMAND))
> +    if (range_covers_byte(addr, l, PCI_COMMAND)) {
>          pci_update_irq_disabled(d, was_irq_disabled);
> +        memory_region_set_enabled(&d->bus_master_enable_region,
> +                                  pci_get_word(d->config + PCI_COMMAND)
> +                                    & PCI_COMMAND_MASTER);
> +    }
>
>      msi_write_config(d, addr, val, l);
>      msix_write_config(d, addr, val, l);
> diff --git a/hw/pci.h b/hw/pci.h
> index 3192d81..a65e490 100644
> --- a/hw/pci.h
> +++ b/hw/pci.h
> @@ -212,6 +212,7 @@ struct PCIDevice {
>      char name[64];
>      PCIIORegion io_regions[PCI_NUM_REGIONS];
>      AddressSpace bus_master_as;
> +    MemoryRegion bus_master_enable_region;
>      DMAContext *dma;
>
>      /* do not access the following fields */
> --
> 1.7.12
>