Re: [Qemu-devel] [patch v4 09/16] memory: introduce mmio request pending to anti nested DMA

[liu ping fan <qemulist@gmail.com>]

On Tue, Oct 23, 2012 at 8:38 PM, Gleb Natapov <gleb@redhat.com> wrote:
> On Mon, Oct 22, 2012 at 05:23:52PM +0800, Liu Ping Fan wrote:
>> Rejecting the nested mmio request which does not aim at RAM, so we
>> can avoid the potential deadlock caused by the random lock sequence
>> of two device's local lock.
>>
>> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
>> ---
>>  cpus.c              |   14 ++++++++++++++
>>  exec.c              |   50 ++++++++++++++++++++++++++++++++++++--------------
>>  hw/hw.h             |    1 +
>>  kvm-all.c           |    2 ++
>>  qemu-thread-posix.h |    3 +++
>>  qemu-thread.h       |    2 ++
>>  6 files changed, 58 insertions(+), 14 deletions(-)
>>
>> diff --git a/cpus.c b/cpus.c
>> index 4cd7f85..365a512 100644
>> --- a/cpus.c
>> +++ b/cpus.c
>> @@ -729,6 +729,18 @@ static void qemu_kvm_wait_io_event(CPUArchState *env)
>>      qemu_wait_io_event_common(env);
>>  }
>>
>> +int get_context_type(void)
>> +{
>> +    QemuThread *t = pthread_getspecific(qemu_thread_key);
>> +    return t->context_type;
>> +}
>> +
> You defined the function but not use it.
>
> What 0/1 context_type means?
>
Will s/t->context/get_context_type/ . The context_type is just for
device's function to tell whether it is called by local lock or
biglock.  0 is initial value, 1 is under mmio dispatching, 2 is under
io dispatching.  Will use enum to define them.

Regards,
pingfan
>> +void set_context_type(int type)
>> +{
>> +    QemuThread *t = pthread_getspecific(qemu_thread_key);
>> +    t->context_type = type;
>> +}
>> +
>>  static void *qemu_kvm_cpu_thread_fn(void *arg)
>>  {
>>      CPUArchState *env = arg;
>> @@ -736,6 +748,8 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
>>      int r;
>>
>>      pthread_setspecific(qemu_thread_key, cpu->thread);
>> +    set_context_type(0);
>> +
>>      qemu_mutex_lock(&qemu_global_mutex);
>>      qemu_thread_get_self(cpu->thread);
>>      env->thread_id = qemu_get_thread_id();
>> diff --git a/exec.c b/exec.c
>> index 91b859b..a0327a1 100644
>> --- a/exec.c
>> +++ b/exec.c
>> @@ -3490,7 +3490,9 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
>>      uint32_t val;
>>      target_phys_addr_t page;
>>      MemoryRegionSection *section, obj_mrs;
>> -    int safe_ref;
>> +    int safe_ref, nested_dma = 0;
>> +    QemuThread *thread = pthread_getspecific(qemu_thread_key);
>> +    int context = thread->context_type;
>>
>>      while (len > 0) {
>>          page = addr & TARGET_PAGE_MASK;
>> @@ -3500,7 +3502,8 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
>>          qemu_mutex_lock(&mem_map_lock);
>>          safe_ref = phys_page_lookup(page, &obj_mrs);
>>          qemu_mutex_unlock(&mem_map_lock);
>> -        if (safe_ref == 0) {
>> +
>> +        if (safe_ref == 0 && context == 1) {
>>              qemu_mutex_lock_iothread();
>>              qemu_mutex_lock(&mem_map_lock);
>>              /* At the 2nd try, mem map can change, so need to judge it again */
>> @@ -3511,7 +3514,9 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
>>              }
>>          }
>>          section = &obj_mrs;
>> -
>> +        if (context == 1) {
>> +            nested_dma = thread->mmio_request_pending++ > 1 ? 1 : 0;
>> +        }
>>          if (is_write) {
>>              if (!memory_region_is_ram(section->mr)) {
>>                  target_phys_addr_t addr1;
>> @@ -3521,17 +3526,23 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
>>                  if (l >= 4 && ((addr1 & 3) == 0)) {
>>                      /* 32 bit write access */
>>                      val = ldl_p(buf);
>> -                    io_mem_write(section->mr, addr1, val, 4);
>> +                    if (!nested_dma) {
>> +                        io_mem_write(section->mr, addr1, val, 4);
>> +                    }
>>                      l = 4;
>>                  } else if (l >= 2 && ((addr1 & 1) == 0)) {
>>                      /* 16 bit write access */
>>                      val = lduw_p(buf);
>> -                    io_mem_write(section->mr, addr1, val, 2);
>> +                    if (!nested_dma) {
>> +                        io_mem_write(section->mr, addr1, val, 2);
>> +                    }
>>                      l = 2;
>>                  } else {
>>                      /* 8 bit write access */
>>                      val = ldub_p(buf);
>> -                    io_mem_write(section->mr, addr1, val, 1);
>> +                    if (!nested_dma) {
>> +                        io_mem_write(section->mr, addr1, val, 1);
>> +                    }
>>                      l = 1;
>>                  }
>>              } else if (!section->readonly) {
>> @@ -3552,24 +3563,31 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
>>              }
>>          } else {
>>              if (!(memory_region_is_ram(section->mr) ||
>> -                  memory_region_is_romd(section->mr))) {
>> +                  memory_region_is_romd(section->mr)) &&
>> +                    !nested_dma) {
>>                  target_phys_addr_t addr1;
>>                  /* I/O case */
>>                  addr1 = memory_region_section_addr(section, addr);
>>                  if (l >= 4 && ((addr1 & 3) == 0)) {
>>                      /* 32 bit read access */
>> -                    val = io_mem_read(section->mr, addr1, 4);
>> -                    stl_p(buf, val);
>> +                    if (!nested_dma) {
>> +                        val = io_mem_read(section->mr, addr1, 4);
>> +                        stl_p(buf, val);
>> +                    }
>>                      l = 4;
>>                  } else if (l >= 2 && ((addr1 & 1) == 0)) {
>>                      /* 16 bit read access */
>> -                    val = io_mem_read(section->mr, addr1, 2);
>> -                    stw_p(buf, val);
>> +                    if (!nested_dma) {
>> +                        val = io_mem_read(section->mr, addr1, 2);
>> +                        stw_p(buf, val);
>> +                    }
>>                      l = 2;
>>                  } else {
>>                      /* 8 bit read access */
>> -                    val = io_mem_read(section->mr, addr1, 1);
>> -                    stb_p(buf, val);
>> +                    if (!nested_dma) {
>> +                        val = io_mem_read(section->mr, addr1, 1);
>> +                        stb_p(buf, val);
>> +                    }
>>                      l = 1;
>>                  }
>>              } else {
>> @@ -3586,7 +3604,11 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
>>          len -= l;
>>          buf += l;
>>          addr += l;
>> -        if (safe_ref == 0) {
>> +
>> +        if (context == 1) {
>> +            thread->mmio_request_pending--;
>> +        }
>> +        if (safe_ref == 0 && context == 1) {
>>              qemu_mutex_unlock_iothread();
>>          }
>>      }
>> diff --git a/hw/hw.h b/hw/hw.h
>> index e5cb9bf..935b045 100644
>> --- a/hw/hw.h
>> +++ b/hw/hw.h
>> @@ -12,6 +12,7 @@
>>  #include "irq.h"
>>  #include "qemu-file.h"
>>  #include "vmstate.h"
>> +#include "qemu-thread.h"
>>
>>  #ifdef NEED_CPU_H
>>  #if TARGET_LONG_BITS == 64
>> diff --git a/kvm-all.c b/kvm-all.c
>> index 34b02c1..b3fa597 100644
>> --- a/kvm-all.c
>> +++ b/kvm-all.c
>> @@ -1562,10 +1562,12 @@ int kvm_cpu_exec(CPUArchState *env)
>>              break;
>>          case KVM_EXIT_MMIO:
>>              DPRINTF("handle_mmio\n");
>> +            set_context_type(1);
>>              cpu_physical_memory_rw(run->mmio.phys_addr,
>>                                     run->mmio.data,
>>                                     run->mmio.len,
>>                                     run->mmio.is_write);
>> +            set_context_type(0);
>>              ret = 0;
>>              break;
>>          case KVM_EXIT_IRQ_WINDOW_OPEN:
>> diff --git a/qemu-thread-posix.h b/qemu-thread-posix.h
>> index 2607b1c..9fcc6f8 100644
>> --- a/qemu-thread-posix.h
>> +++ b/qemu-thread-posix.h
>> @@ -12,6 +12,9 @@ struct QemuCond {
>>
>>  struct QemuThread {
>>      pthread_t thread;
>> +    /* 0 clean; 1 mmio; 2 io */
>> +    int context_type;
>> +    int mmio_request_pending;
>>  };
>>
>>  extern pthread_key_t qemu_thread_key;
>> diff --git a/qemu-thread.h b/qemu-thread.h
>> index 4a6427d..88eaf94 100644
>> --- a/qemu-thread.h
>> +++ b/qemu-thread.h
>> @@ -45,6 +45,8 @@ void *qemu_thread_join(QemuThread *thread);
>>  void qemu_thread_get_self(QemuThread *thread);
>>  bool qemu_thread_is_self(QemuThread *thread);
>>  void qemu_thread_exit(void *retval);
>> +int get_context_type(void);
>> +void set_context_type(int type);
>>
>>  void qemu_thread_key_create(void);
>>  #endif
>> --
>> 1.7.4.4
>>
>
> --
>                         Gleb.
>