Re: [PATCH 1/3] Enable non page boundary BAR device assignment

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Dec 15, 2009 at 08:04:10PM +0100, Alexander Graf wrote:
> Michael S. Tsirkin wrote:
> > On Tue, Dec 15, 2009 at 07:47:35PM +0100, Alexander Graf wrote:
> >   
> >> Michael S. Tsirkin wrote:
> >>     
> >>> On Tue, Dec 15, 2009 at 07:30:26PM +0100, Alexander Graf wrote:
> >>>   
> >>>       
> >>>> While trying to get device passthrough working with an emulex hba, kvm
> >>>> refused to pass it through because it has a BAR of 256 bytes:
> >>>>
> >>>>         Region 0: Memory at d2100000 (64-bit, non-prefetchable) [size=4K]
> >>>>         Region 2: Memory at d2101000 (64-bit, non-prefetchable) [size=256]
> >>>>         Region 4: I/O ports at b100 [size=256]
> >>>>
> >>>> Since the page boundary is an arbitrary optimization to allow 1:1 mapping of
> >>>> physical to virtual addresses, we can still take the old MMIO callback route.
> >>>>
> >>>> So let's add a second code path that allows for size & 0xFFF != 0 sized regions
> >>>> by looping it through userspace.
> >>>>
> >>>> I verified that it works by passing through an e1000 with this additional patch
> >>>> applied and the card acted the same way it did without this patch:
> >>>>
> >>>>              map_func = assigned_dev_iomem_map;
> >>>> -            if (cur_region->size & 0xFFF) {
> >>>> +            if (i != PCI_ROM_SLOT){
> >>>>                  fprintf(stderr, "PCI region %d at address 0x%llx "
> >>>>
> >>>> Signed-off-by: Alexander Graf <agraf@suse.de>
> >>>>     
> >>>>         
> >>> Looks good.
> >>> 1 question:
> >>>
> >>>   
> >>>       
> >>>> ---
> >>>>
> >>>> v1 -> v2:
> >>>>
> >>>>   - don't use map_func function pointer
> >>>>   - use the same code for mmap on fast and slow path
> >>>>
> >>>> v2 -> v3:
> >>>>
> >>>>   - address mst's comments
> >>>> ---
> >>>>  hw/device-assignment.c |  117 +++++++++++++++++++++++++++++++++++++++++++++--
> >>>>  1 files changed, 112 insertions(+), 5 deletions(-)
> >>>>
> >>>> diff --git a/hw/device-assignment.c b/hw/device-assignment.c
> >>>> index 13a86bb..000fa61 100644
> >>>> --- a/hw/device-assignment.c
> >>>> +++ b/hw/device-assignment.c
> >>>> @@ -148,6 +148,105 @@ static uint32_t assigned_dev_ioport_readl(void *opaque, uint32_t addr)
> >>>>      return value;
> >>>>  }
> >>>>  
> >>>> +static uint32_t slow_bar_readb(void *opaque, target_phys_addr_t addr)
> >>>> +{
> >>>> +    AssignedDevRegion *d = opaque;
> >>>> +    uint8_t *in = d->u.r_virtbase + addr;
> >>>> +    uint32_t r;
> >>>> +
> >>>> +    r = *in;
> >>>> +    DEBUG("slow_bar_readl addr=0x" TARGET_FMT_plx " val=0x%08x\n", addr, r);
> >>>> +
> >>>> +    return r;
> >>>> +}
> >>>> +
> >>>> +static uint32_t slow_bar_readw(void *opaque, target_phys_addr_t addr)
> >>>> +{
> >>>> +    AssignedDevRegion *d = opaque;
> >>>> +    uint16_t *in = d->u.r_virtbase + addr;
> >>>> +    uint32_t r;
> >>>> +
> >>>> +    r = *in;
> >>>> +    DEBUG("slow_bar_readl addr=0x" TARGET_FMT_plx " val=0x%08x\n", addr, r);
> >>>> +
> >>>> +    return r;
> >>>> +}
> >>>> +
> >>>> +static uint32_t slow_bar_readl(void *opaque, target_phys_addr_t addr)
> >>>> +{
> >>>> +    AssignedDevRegion *d = opaque;
> >>>> +    uint32_t *in = d->u.r_virtbase + addr;
> >>>> +    uint32_t r;
> >>>> +
> >>>> +    r = *in;
> >>>> +    DEBUG("slow_bar_readl addr=0x" TARGET_FMT_plx " val=0x%08x\n", addr, r);
> >>>> +
> >>>> +    return r;
> >>>> +}
> >>>> +
> >>>> +static void slow_bar_writeb(void *opaque, target_phys_addr_t addr, uint32_t val)
> >>>> +{
> >>>> +    AssignedDevRegion *d = opaque;
> >>>> +    uint8_t *out = d->u.r_virtbase + addr;
> >>>> +
> >>>> +    DEBUG("slow_bar_writeb addr=0x" TARGET_FMT_plx " val=0x%02x\n", addr, val);
> >>>> +    *out = val;
> >>>> +}
> >>>> +
> >>>> +static void slow_bar_writew(void *opaque, target_phys_addr_t addr, uint32_t val)
> >>>> +{
> >>>> +    AssignedDevRegion *d = opaque;
> >>>> +    uint16_t *out = d->u.r_virtbase + addr;
> >>>> +
> >>>> +    DEBUG("slow_bar_writew addr=0x" TARGET_FMT_plx " val=0x%04x\n", addr, val);
> >>>> +    *out = val;
> >>>> +}
> >>>> +
> >>>> +static void slow_bar_writel(void *opaque, target_phys_addr_t addr, uint32_t val)
> >>>> +{
> >>>> +    AssignedDevRegion *d = opaque;
> >>>> +    uint32_t *out = d->u.r_virtbase + addr;
> >>>> +
> >>>> +    DEBUG("slow_bar_writel addr=0x" TARGET_FMT_plx " val=0x%08x\n", addr, val);
> >>>> +    *out = val;
> >>>> +}
> >>>> +
> >>>> +static CPUWriteMemoryFunc * const slow_bar_write[] = {
> >>>> +    &slow_bar_writeb,
> >>>> +    &slow_bar_writew,
> >>>> +    &slow_bar_writel
> >>>> +};
> >>>> +
> >>>> +static CPUReadMemoryFunc * const slow_bar_read[] = {
> >>>> +    &slow_bar_readb,
> >>>> +    &slow_bar_readw,
> >>>> +    &slow_bar_readl
> >>>> +};
> >>>> +
> >>>> +static void assigned_dev_iomem_map_slow(PCIDevice *pci_dev, int region_num,
> >>>> +                                        pcibus_t e_phys, pcibus_t e_size,
> >>>> +                                        int type)
> >>>> +{
> >>>> +    AssignedDevice *r_dev = container_of(pci_dev, AssignedDevice, dev);
> >>>> +    AssignedDevRegion *region = &r_dev->v_addrs[region_num];
> >>>> +    PCIRegion *real_region = &r_dev->real_device.regions[region_num];
> >>>> +    int m;
> >>>> +
> >>>> +    DEBUG("slow map\n");
> >>>> +    m = cpu_register_io_memory(slow_bar_read, slow_bar_write, region);
> >>>> +    cpu_register_physical_memory(e_phys, e_size, m);
> >>>> +
> >>>> +    /* MSI-X MMIO page */
> >>>> +    if ((e_size > 0) &&
> >>>> +        real_region->base_addr <= r_dev->msix_table_addr &&
> >>>> +        real_region->base_addr + real_region->size >= r_dev->msix_table_addr) {
> >>>> +        int offset = r_dev->msix_table_addr - real_region->base_addr;
> >>>> +
> >>>> +        cpu_register_physical_memory(e_phys + offset,
> >>>> +                TARGET_PAGE_SIZE, r_dev->mmio_index);
> >>>> +    }
> >>>> +}
> >>>> +
> >>>>  static void assigned_dev_iomem_map(PCIDevice *pci_dev, int region_num,
> >>>>                                     pcibus_t e_phys, pcibus_t e_size, int type)
> >>>>  {
> >>>> @@ -381,15 +480,22 @@ static int assigned_dev_register_regions(PCIRegion *io_regions,
> >>>>  
> >>>>          /* handle memory io regions */
> >>>>          if (cur_region->type & IORESOURCE_MEM) {
> >>>> +            int slow_map = 0;
> >>>>              int t = cur_region->type & IORESOURCE_PREFETCH
> >>>>                  ? PCI_BASE_ADDRESS_MEM_PREFETCH
> >>>>                  : PCI_BASE_ADDRESS_SPACE_MEMORY;
> >>>> +
> >>>>              if (cur_region->size & 0xFFF) {
> >>>> -                fprintf(stderr, "Unable to assign device: PCI region %d "
> >>>> -                        "at address 0x%llx has size 0x%x, "
> >>>> -                        " which is not a multiple of 4K\n",
> >>>> +                fprintf(stderr, "PCI region %d at address 0x%llx "
> >>>> +                        "has size 0x%x, which is not a multiple of 4K. "
> >>>> +                        "You might experience some performance hit due to that.\n",
> >>>>                          i, (unsigned long long)cur_region->base_addr,
> >>>>                          cur_region->size);
> >>>> +                slow_map = 1;
> >>>> +            }
> >>>> +
> >>>> +            if (slow_map && (i == PCI_ROM_SLOT)) {
> >>>> +                fprintf(stderr, "ROM not aligned - can't continue\n");
> >>>>                  return -1;
> >>>>     
> >>>>         
> >>> Why is this? Can't ROM be handled in the same way?
> >>> I think it was previously ...
> >>>   
> >>>       
> >> You can't execute code from MMIO regions, so slow_map doesn't work there.
> >>     
> >
> > Hmm, how does it work with passthrough?
> > Anyway, I don't think a lot of users run ROM
> > code directly, they just shadow it and run from there.
> >
> >   
> >>>   
> >>>       
> >>>>              }
> >>>>  
> >>>> @@ -405,7 +511,7 @@ static int assigned_dev_register_regions(PCIRegion *io_regions,
> >>>>              } else {
> >>>>                  pci_dev->v_addrs[i].u.r_virtbase =
> >>>>                      mmap(NULL,
> >>>> -                         (cur_region->size + 0xFFF) & 0xFFFFF000,
> >>>> +                         cur_region->size,
> >>>>     
> >>>>         
> >>> Hmm, one assumes this code did work at some point ...
> >>> do you know why was it done this way?
> >>>   
> >>>       
> >> Nope :-).
> >>     
> >
> > So maybe keep it that way or make the change in a separate patch.
> >   
> 
> Well we're sure the normal path is size aligned, no? In fact, you
> recommended I should change the code to what this looks like ;-).
> 
> Alex


Existing code first page aligned address, passes this to mmap,
then adds page offset. I do not know why. Could be e.g. to handle
different libc/kernel versions. If we are not sure it is
not needed, let's keep it this way. If we are sure, let's
cleanup in a separate patch. Makes sense?

-- 
MST