Re: [Qemu-devel] [PATCH V2 4/7] exec: allow to get a pointer for some mmio memory region

[Frederic Konrad]

On 03/03/2017 02:44 PM, Edgar E. Iglesias wrote:
> On Fri, Feb 17, 2017 at 09:17:10PM +0100, address@hidden wrote:
>> From: KONRAD Frederic <address@hidden>
>>
>> This introduces a special callback which allows to run code from some MMIO
>> devices.
>>
>> SysBusDevice with a MemoryRegion which implements the request_ptr callback 
>> will
>> be notified when the guest try to execute code from their offset. Then it 
>> will
>> be able to eg: pre-load some code from an SPI device or ask a pointer from an
>> external simulator, etc..
>>
>> When the pointer or the data in it are no longer valid the device has to
>> invalidate it.
>>
>> Signed-off-by: KONRAD Frederic <address@hidden>
>>
>> RFC -> V1:
>>   * Use mmio-interface instead of directly creating the subregion.
> 
> Hi Fred,
> 
> 
> 
> 
>> ---
>>  cputlb.c              |  7 +++++++
>>  include/exec/memory.h | 35 +++++++++++++++++++++++++++++++
>>  memory.c              | 57 
>> +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 99 insertions(+)
>>
>> diff --git a/cputlb.c b/cputlb.c
>> index 846341e..9077247 100644
>> --- a/cputlb.c
>> +++ b/cputlb.c
>> @@ -545,6 +545,13 @@ tb_page_addr_t get_page_addr_code(CPUArchState *env, 
>> target_ulong addr)
>>      if (memory_region_is_unassigned(mr)) {
>>          CPUClass *cc = CPU_GET_CLASS(cpu);
>>  
>> +        if (memory_region_request_mmio_ptr(mr, addr)) {
>> +            /* A MemoryRegion is potentially added so re-run the
>> +             * get_page_addr_code.
>> +             */
>> +            return get_page_addr_code(env, addr);
>> +        }
>> +
>>          if (cc->do_unassigned_access) {
>>              cc->do_unassigned_access(cpu, addr, false, true, 0, 4);
>>          } else {
>> diff --git a/include/exec/memory.h b/include/exec/memory.h
>> index 987f925..36b0eec 100644
>> --- a/include/exec/memory.h
>> +++ b/include/exec/memory.h
>> @@ -120,6 +120,15 @@ struct MemoryRegionOps {
>>                                      uint64_t data,
>>                                      unsigned size,
>>                                      MemTxAttrs attrs);
>> +    /* Instruction execution pre-callback:
>> +     * @addr is the address of the access relative to the @mr.
>> +     * @size is the size of the area returned by the callback.
>> +     * @offset is the location of the pointer inside @mr.
>> +     *
>> +     * Returns a pointer to a location which contains guest code.
>> +     */
>> +    void *(*request_ptr)(void *opaque, hwaddr addr, unsigned *size,
>> +                         unsigned *offset);
>>  
>>      enum device_endian endianness;
>>      /* Guest-visible constraints: */
>> @@ -1253,6 +1262,32 @@ void memory_global_dirty_log_stop(void);
>>  void mtree_info(fprintf_function mon_printf, void *f, bool flatview);
>>  
>>  /**
>> + * memory_region_request_mmio_ptr: request a pointer to an mmio
>> + * MemoryRegion. If it is possible map a RAM MemoryRegion with this pointer.
>> + * When the device wants to invalidate the pointer it will call
>> + * memory_region_invalidate_mmio_ptr.
>> + *
>> + * @mr: #MemoryRegion to check
>> + * @addr: address within that region
>> + *
>> + * Returns true on success, false otherwise.
>> + */
>> +bool memory_region_request_mmio_ptr(MemoryRegion *mr, hwaddr addr);
>> +
>> +/**
>> + * memory_region_invalidate_mmio_ptr: invalidate the pointer to an mmio
>> + * previously requested.
>> + * In the end that means that if something wants to execute from this area 
>> it
>> + * will need to request the pointer again.
>> + *
>> + * @mr: #MemoryRegion associated to the pointer.
>> + * @addr: address within that region
>> + * @size: size of that area.
>> + */
>> +void memory_region_invalidate_mmio_ptr(MemoryRegion *mr, hwaddr offset,
>> +                                       unsigned size);
>> +
>> +/**
>>   * memory_region_dispatch_read: perform a read directly to the specified
>>   * MemoryRegion.
>>   *
>> diff --git a/memory.c b/memory.c
>> index 6c58373..a605250 100644
>> --- a/memory.c
>> +++ b/memory.c
>> @@ -30,6 +30,8 @@
>>  #include "exec/ram_addr.h"
>>  #include "sysemu/kvm.h"
>>  #include "sysemu/sysemu.h"
>> +#include "hw/misc/mmio_interface.h"
>> +#include "hw/qdev-properties.h"
>>  
>>  //#define DEBUG_UNASSIGNED
>>  
>> @@ -2375,6 +2377,61 @@ void memory_listener_unregister(MemoryListener 
>> *listener)
>>      QTAILQ_REMOVE(&listener->address_space->listeners, listener, link_as);
>>  }
>>  
>> +bool memory_region_request_mmio_ptr(MemoryRegion *mr, hwaddr addr)
>> +{
>> +    void *host;
>> +    unsigned size = 0;
>> +    unsigned offset = 0;
>> +    Object *new_interface;
>> +
>> +    if (!mr || !mr->ops->request_ptr) {
>> +        return false;
>> +    }
>> +
>> +    /*
>> +     * Avoid an update if the request_ptr call
>> +     * memory_region_invalidate_mmio_ptr which seems to be likely when we 
>> use
>> +     * a cache.
>> +     */
>> +    memory_region_transaction_begin();
>> +
>> +    host = mr->ops->request_ptr(mr->opaque, addr - mr->addr, &size, 
>> &offset);
>> +
>> +    if (!host || !size) {
>> +        memory_region_transaction_commit();
>> +        return false;
>> +    }
>> +
>> +    new_interface = object_new("mmio_interface");
>> +    qdev_prop_set_uint64(DEVICE(new_interface), "start", offset);
>> +    qdev_prop_set_uint64(DEVICE(new_interface), "end", offset + size - 1);
>> +    qdev_prop_set_bit(DEVICE(new_interface), "ro", true);
>> +    qdev_prop_set_ptr(DEVICE(new_interface), "host_ptr", host);
>> +    qdev_prop_set_ptr(DEVICE(new_interface), "subregion", mr);
>> +    object_property_set_bool(OBJECT(new_interface), true, "realized", NULL);
>> +
>> +    memory_region_transaction_commit();
>> +    return true;
>> +}
>> +
>> +void memory_region_invalidate_mmio_ptr(MemoryRegion *mr, hwaddr offset,
>> +                                       unsigned size)
>> +{
>> +    MemoryRegionSection section = memory_region_find(mr, offset, size);
>> +
>> +    if (section.mr != mr) {
>> +        /* memory_region_find add a ref on section.mr */
>> +        memory_region_unref(section.mr);
>> +        if (!MMIO_INTERFACE(section.mr->owner)) {
> 
> Is MMIO_INTERFACE defined yet?
> This may break bisection...

OOPS, your right :(..
I'll resend with the right order!

Thanks!
Fred

> 
> Cheers,
> Edgar
> 
> 
>> +            return;
>> +        }
>> +        /* We found the interface just drop it. */
>> +        object_property_set_bool(section.mr->owner, false, "realized", 
>> NULL);
>> +        object_unref(section.mr->owner);
>> +        object_unparent(section.mr->owner);
>> +    }
>> +}
>> +
>>  void address_space_init(AddressSpace *as, MemoryRegion *root, const char 
>> *name)
>>  {
>>      memory_region_ref(root);
>> -- 
>> 1.8.3.1
>>
>>