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

Alexander Graf
2009-12-15T19:04:11Z

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