On 09/24/2012 10:32 AM, liu ping fan wrote: > On Mon, Sep 24, 2012 at 3:44 PM, Avi Kivity <a...@redhat.com> wrote: >> On 09/24/2012 08:33 AM, liu ping fan wrote: >>> On Wed, Sep 19, 2012 at 5:50 PM, Avi Kivity <a...@redhat.com> wrote: >>> > On 09/19/2012 12:34 PM, Jan Kiszka wrote: >>> >> >>> >> What about the following: >>> >> >>> >> What we really need to support in practice is MMIO access triggers RAM >>> >> access of device model. Scenarios where a device access triggers another >>> >> MMIO access could likely just be rejected without causing troubles. >>> >> >>> >> So, when we dispatch a request to a device, we mark that the current >>> >> thread is in a MMIO dispatch and reject any follow-up c_p_m_rw that does >>> >> _not_ target RAM, ie. is another, nested MMIO request - independent of >>> >> its destination. How much of the known issues would this solve? And what >>> >> would remain open? >>> > >>> > Various iommu-like devices re-dispatch I/O, like changing endianness or >>> > bitband. I don't know whether it targets I/O rather than RAM. >>> > >>> Have not found the exact code. But I think the call chain may look >>> like this: dev mmio-handler --> c_p_m_rw() --> iommu mmio-handler --> >>> c_p_m_rw() >>> And I think you worry about the case for "c_p_m_rw() --> iommu >>> mmio-handler". Right? How about introduce an member can_nest for >>> MemoryRegionOps of iommu's mr? >>> >> >> I would rather push the iommu logic into the memory API: >> >> memory_region_init_iommu(MemoryRegion *mr, const char *name, >> MemoryRegion *target, MemoryRegionIOMMUOps *ops, >> unsigned size) >> >> struct MemoryRegionIOMMUOps { >> target_physical_addr_t (*translate)(target_physical_addr_t addr, >> bool write); >> void (*fault)(target_physical_addr_t addr); >> }; >> > So I guess, after introduce this, the code logic in c_p_m_rw() will > look like this > > c_p_m_rw(dev_virt_addr, ...) > { > mr = phys_page_lookup(); > if (mr->iommu_ops) > real_addr = translate(dev_virt_addr,..); > > ptr = qemu_get_ram_ptr(real_addr); > memcpy(buf, ptr, sz); > } >
Something like that. It will be a while loop, to allow for iommus strung in series. -- error compiling committee.c: too many arguments to function