[PATCH-for-5.2] exec: Remove MemoryRegion::global_locking field

[PATCH-for-5.2] exec: Remove MemoryRegion::global_locking field

[Philippe Mathieu-Daudé]

Last uses of memory_region_clear_global_locking() have been
removed in commit 7070e085d4 ("acpi: mark PMTIMER as unlocked")
and commit 08565552f7 ("cputlb: Move NOTDIRTY handling from I/O
path to TLB path").
Remove memory_region_clear_global_locking() and the now unused
'global_locking' field in MemoryRegion.

Reported-by: Alexander Bulekov <alxndr@bu.edu>
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 include/exec/memory.h | 14 --------------
 accel/tcg/cputlb.c    |  4 ++--
 exec.c                |  2 +-
 softmmu/memory.c      |  6 ------
 4 files changed, 3 insertions(+), 23 deletions(-)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 307e527835..bb84283376 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -377,7 +377,6 @@ struct MemoryRegion {
     bool nonvolatile;
     bool rom_device;
     bool flush_coalesced_mmio;
-    bool global_locking;
     uint8_t dirty_log_mask;
     bool is_iommu;
     RAMBlock *ram_block;
@@ -1711,19 +1710,6 @@ void memory_region_set_flush_coalesced(MemoryRegion *mr);
  */
 void memory_region_clear_flush_coalesced(MemoryRegion *mr);
 
-/**
- * memory_region_clear_global_locking: Declares that access processing does
- *                                     not depend on the QEMU global lock.
- *
- * By clearing this property, accesses to the memory region will be processed
- * outside of QEMU's global lock (unless the lock is held on when issuing the
- * access request). In this case, the device model implementing the access
- * handlers is responsible for synchronization of concurrency.
- *
- * @mr: the memory region to be updated.
- */
-void memory_region_clear_global_locking(MemoryRegion *mr);
-
 /**
  * memory_region_add_eventfd: Request an eventfd to be triggered when a word
  *                            is written to a location.
diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index 5698292749..9ddf2b8dfa 100644
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -1053,7 +1053,7 @@ static uint64_t io_readx(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
         cpu_io_recompile(cpu, retaddr);
     }
 
-    if (mr->global_locking && !qemu_mutex_iothread_locked()) {
+    if (!qemu_mutex_iothread_locked()) {
         qemu_mutex_lock_iothread();
         locked = true;
     }
@@ -1114,7 +1114,7 @@ static void io_writex(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
      */
     save_iotlb_data(cpu, iotlbentry->addr, section, mr_offset);
 
-    if (mr->global_locking && !qemu_mutex_iothread_locked()) {
+    if (!qemu_mutex_iothread_locked()) {
         qemu_mutex_lock_iothread();
         locked = true;
     }
diff --git a/exec.c b/exec.c
index 6f381f98e2..05cfc34b6c 100644
--- a/exec.c
+++ b/exec.c
@@ -3135,7 +3135,7 @@ static bool prepare_mmio_access(MemoryRegion *mr)
     bool unlocked = !qemu_mutex_iothread_locked();
     bool release_lock = false;
 
-    if (unlocked && mr->global_locking) {
+    if (unlocked) {
         qemu_mutex_lock_iothread();
         unlocked = false;
         release_lock = true;
diff --git a/softmmu/memory.c b/softmmu/memory.c
index af25987518..2303747feb 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -1221,7 +1221,6 @@ static void memory_region_initfn(Object *obj)
     mr->ops = &unassigned_mem_ops;
     mr->enabled = true;
     mr->romd_mode = true;
-    mr->global_locking = true;
     mr->destructor = memory_region_destructor_none;
     QTAILQ_INIT(&mr->subregions);
     QTAILQ_INIT(&mr->coalesced);
@@ -2277,11 +2276,6 @@ void memory_region_clear_flush_coalesced(MemoryRegion *mr)
     }
 }
 
-void memory_region_clear_global_locking(MemoryRegion *mr)
-{
-    mr->global_locking = false;
-}
-
 static bool userspace_eventfd_warning;
 
 void memory_region_add_eventfd(MemoryRegion *mr,
-- 
2.21.3

Re: [PATCH-for-5.2] exec: Remove MemoryRegion::global_locking field

[Stefan Hajnoczi]

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On Thu, Aug 06, 2020 at 05:07:26PM +0200, Philippe Mathieu-Daudé wrote:
> Last uses of memory_region_clear_global_locking() have been
> removed in commit 7070e085d4 ("acpi: mark PMTIMER as unlocked")
> and commit 08565552f7 ("cputlb: Move NOTDIRTY handling from I/O
> path to TLB path").
> Remove memory_region_clear_global_locking() and the now unused
> 'global_locking' field in MemoryRegion.
> 
> Reported-by: Alexander Bulekov <alxndr@bu.edu>
> Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  include/exec/memory.h | 14 --------------
>  accel/tcg/cputlb.c    |  4 ++--
>  exec.c                |  2 +-
>  softmmu/memory.c      |  6 ------
>  4 files changed, 3 insertions(+), 23 deletions(-)

It can be added back in later, if necessary. For now let's drop the dead
code.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [PATCH-for-5.2] exec: Remove MemoryRegion::global_locking field

[Paolo Bonzini]

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On 07/08/20 12:02, Stefan Hajnoczi wrote:
> On Thu, Aug 06, 2020 at 05:07:26PM +0200, Philippe Mathieu-Daudé wrote:
>> Last uses of memory_region_clear_global_locking() have been
>> removed in commit 7070e085d4 ("acpi: mark PMTIMER as unlocked")
>> and commit 08565552f7 ("cputlb: Move NOTDIRTY handling from I/O
>> path to TLB path").
>> Remove memory_region_clear_global_locking() and the now unused
>> 'global_locking' field in MemoryRegion.
>>
>> Reported-by: Alexander Bulekov <alxndr@bu.edu>
>> Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> ---
>>  include/exec/memory.h | 14 --------------
>>  accel/tcg/cputlb.c    |  4 ++--
>>  exec.c                |  2 +-
>>  softmmu/memory.c      |  6 ------
>>  4 files changed, 3 insertions(+), 23 deletions(-)
> 
> It can be added back in later, if necessary. For now let's drop the dead
> code.
> 
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> 

I expect it will come back since Linaro is working on BQL-free interrupt
handling for TCG, but no objections.

Paolo


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Re: [PATCH-for-5.2] exec: Remove MemoryRegion::global_locking field

[Philippe Mathieu-Daudé]

+Robert

On 8/7/20 12:16 PM, Paolo Bonzini wrote:
> On 07/08/20 12:02, Stefan Hajnoczi wrote:
>> On Thu, Aug 06, 2020 at 05:07:26PM +0200, Philippe Mathieu-Daudé wrote:
>>> Last uses of memory_region_clear_global_locking() have been
>>> removed in commit 7070e085d4 ("acpi: mark PMTIMER as unlocked")
>>> and commit 08565552f7 ("cputlb: Move NOTDIRTY handling from I/O
>>> path to TLB path").
>>> Remove memory_region_clear_global_locking() and the now unused
>>> 'global_locking' field in MemoryRegion.
>>>
>>> Reported-by: Alexander Bulekov <alxndr@bu.edu>
>>> Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>> ---
>>>  include/exec/memory.h | 14 --------------
>>>  accel/tcg/cputlb.c    |  4 ++--
>>>  exec.c                |  2 +-
>>>  softmmu/memory.c      |  6 ------
>>>  4 files changed, 3 insertions(+), 23 deletions(-)
>>
>> It can be added back in later, if necessary. For now let's drop the dead
>> code.
>>
>> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
>>
> 
> I expect it will come back since Linaro is working on BQL-free interrupt
> handling for TCG, but no objections.

Robert, any comment on this patch?

Thanks,

Phil.

Re: [PATCH-for-5.2] exec: Remove MemoryRegion::global_locking field

[Robert Foley]

On Sat, 22 Aug 2020 at 16:13, Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
>
> +Robert
>
> On 8/7/20 12:16 PM, Paolo Bonzini wrote:
> > On 07/08/20 12:02, Stefan Hajnoczi wrote:
> >> On Thu, Aug 06, 2020 at 05:07:26PM +0200, Philippe Mathieu-Daudé wrote:
> >>> Last uses of memory_region_clear_global_locking() have been
> >>> removed in commit 7070e085d4 ("acpi: mark PMTIMER as unlocked")
> >>> and commit 08565552f7 ("cputlb: Move NOTDIRTY handling from I/O
> >>> path to TLB path").
> >>> Remove memory_region_clear_global_locking() and the now unused
> >>> 'global_locking' field in MemoryRegion.
> >>>
> >>> Reported-by: Alexander Bulekov <alxndr@bu.edu>
> >>> Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
> >>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> >>> ---
> >>>  include/exec/memory.h | 14 --------------
> >>>  accel/tcg/cputlb.c    |  4 ++--
> >>>  exec.c                |  2 +-
> >>>  softmmu/memory.c      |  6 ------
> >>>  4 files changed, 3 insertions(+), 23 deletions(-)
> >>
> >> It can be added back in later, if necessary. For now let's drop the dead
> >> code.
> >>
> >> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> >>
> >
> > I expect it will come back since Linaro is working on BQL-free interrupt
> > handling for TCG, but no objections.
>
> Robert, any comment on this patch?
>
> Thanks,
>
> Phil.
>
Phil, Thanks for the heads up on this !

No objections to removing this.  We can easily re-add it if/when needed.

Thanks,
-Rob