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* [Qemu-devel] [PATCH] vhost-user: avoid misaligned access
@ 2018-03-16 18:20 Michael S. Tsirkin
  2018-03-20  2:01 ` Zhoujian (jay)
  0 siblings, 1 reply; 5+ messages in thread
From: Michael S. Tsirkin @ 2018-03-16 18:20 UTC (permalink / raw)
  To: qemu-devel; +Cc: Jay Zhou

We can't pass a pointer to memory field directly since
it's within a packed structure, so isn't aligned.
Pass a pointer on stack and copy.

Fixes: 30c4cc7 ("vhost: used_memslots refactoring")
Cc: Jay Zhou <jianjay.zhou@huawei.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

I had to apply this to fix make check errors with clang.
Pls review, test and ack.

Thanks!

 hw/virtio/vhost-user.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index c12fdd9..a44ee7f 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -396,6 +396,7 @@ static int vhost_user_set_mem_table_postcopy(struct vhost_dev *dev,
     bool reply_supported = virtio_has_feature(dev->protocol_features,
                                               VHOST_USER_PROTOCOL_F_REPLY_ACK);
     VhostUserMsg msg_reply;
+    VhostUserMemory memory = {};
     int region_i, msg_i;
 
     VhostUserMsg msg = {
@@ -407,10 +408,11 @@ static int vhost_user_set_mem_table_postcopy(struct vhost_dev *dev,
         msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
     }
 
-    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
+    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
         error_report("Failed preparing vhost-user memory table msg");
         return -1;
     }
+    msg.payload.memory = memory;
 
     fd_num = msg.payload.memory.nregions;
 
@@ -549,16 +551,19 @@ static int vhost_user_set_mem_table(struct vhost_dev *dev,
         .hdr.request = VHOST_USER_SET_MEM_TABLE,
         .hdr.flags = VHOST_USER_VERSION,
     };
+    VhostUserMemory memory = {};
 
     if (reply_supported) {
         msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
     }
 
-    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
+    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
         error_report("Failed preparing vhost-user memory table msg");
         return -1;
     }
 
+    msg.payload.memory = memory;
+
     fd_num = msg.payload.memory.nregions;
 
     if (!fd_num) {
@@ -1575,8 +1580,11 @@ static void vhost_user_set_used_memslots(struct vhost_dev *dev)
 {
     int fds[VHOST_MEMORY_MAX_NREGIONS];
     VhostUserMsg msg;
+    VhostUserMemory memory = {};
+
+    vhost_user_prepare_msg(dev, &memory, fds);
 
-    vhost_user_prepare_msg(dev, &msg.payload.memory, fds);
+    msg.payload.memory = memory;
 }
 
 const VhostOps user_ops = {
-- 
MST

^ permalink raw reply related	[flat|nested] 5+ messages in thread

* Re: [Qemu-devel] [PATCH] vhost-user: avoid misaligned access
  2018-03-16 18:20 [Qemu-devel] [PATCH] vhost-user: avoid misaligned access Michael S. Tsirkin
@ 2018-03-20  2:01 ` Zhoujian (jay)
  2018-03-20  2:36   ` Michael S. Tsirkin
  0 siblings, 1 reply; 5+ messages in thread
From: Zhoujian (jay) @ 2018-03-20  2:01 UTC (permalink / raw)
  To: Michael S. Tsirkin, qemu-devel



> -----Original Message-----
> From: Michael S. Tsirkin [mailto:mst@redhat.com]
> Sent: Saturday, March 17, 2018 2:20 AM
> To: qemu-devel@nongnu.org
> Cc: Zhoujian (jay) <jianjay.zhou@huawei.com>
> Subject: [PATCH] vhost-user: avoid misaligned access
> 
> We can't pass a pointer to memory field directly since it's within a packed
> structure, so isn't aligned.
> Pass a pointer on stack and copy.
> 
> Fixes: 30c4cc7 ("vhost: used_memslots refactoring")
> Cc: Jay Zhou <jianjay.zhou@huawei.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> 
> I had to apply this to fix make check errors with clang.
> Pls review, test and ack.
> 
> Thanks!
> 
>  hw/virtio/vhost-user.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index
> c12fdd9..a44ee7f 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -396,6 +396,7 @@ static int vhost_user_set_mem_table_postcopy(struct
> vhost_dev *dev,
>      bool reply_supported = virtio_has_feature(dev->protocol_features,
> 
> VHOST_USER_PROTOCOL_F_REPLY_ACK);
>      VhostUserMsg msg_reply;
> +    VhostUserMemory memory = {};
>      int region_i, msg_i;
> 
>      VhostUserMsg msg = {
> @@ -407,10 +408,11 @@ static int vhost_user_set_mem_table_postcopy(struct
> vhost_dev *dev,
>          msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
>      }
> 
> -    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
> +    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
>          error_report("Failed preparing vhost-user memory table msg");
>          return -1;
>      }
> +    msg.payload.memory = memory;
> 
>      fd_num = msg.payload.memory.nregions;
> 
> @@ -549,16 +551,19 @@ static int vhost_user_set_mem_table(struct vhost_dev
> *dev,
>          .hdr.request = VHOST_USER_SET_MEM_TABLE,
>          .hdr.flags = VHOST_USER_VERSION,
>      };
> +    VhostUserMemory memory = {};
> 
>      if (reply_supported) {
>          msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
>      }
> 
> -    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
> +    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
>          error_report("Failed preparing vhost-user memory table msg");
>          return -1;
>      }
> 
> +    msg.payload.memory = memory;
> +
>      fd_num = msg.payload.memory.nregions;
> 
>      if (!fd_num) {
> @@ -1575,8 +1580,11 @@ static void vhost_user_set_used_memslots(struct
> vhost_dev *dev)  {
>      int fds[VHOST_MEMORY_MAX_NREGIONS];
>      VhostUserMsg msg;
> +    VhostUserMemory memory = {};
> +
> +    vhost_user_prepare_msg(dev, &memory, fds);
> 
> -    vhost_user_prepare_msg(dev, &msg.payload.memory, fds);
> +    msg.payload.memory = memory;
>  }

Hi Michael, here should be like this:


static void vhost_user_set_used_memslots(struct vhost_dev *dev)
 {
     int fds[VHOST_MEMORY_MAX_NREGIONS];
-    VhostUserMsg msg;
+    VhostUserMemory memory = {};
 
-    vhost_user_prepare_msg(dev, &msg.payload.memory, fds);
+    vhost_user_prepare_msg(dev, &memory, fds);
 }


Regards,
Jay

> 
>  const VhostOps user_ops = {
> --
> MST

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [Qemu-devel] [PATCH] vhost-user: avoid misaligned access
  2018-03-20  2:01 ` Zhoujian (jay)
@ 2018-03-20  2:36   ` Michael S. Tsirkin
  2018-03-20  7:05     ` Igor Mammedov
  0 siblings, 1 reply; 5+ messages in thread
From: Michael S. Tsirkin @ 2018-03-20  2:36 UTC (permalink / raw)
  To: Zhoujian (jay); +Cc: qemu-devel

On Tue, Mar 20, 2018 at 02:01:07AM +0000, Zhoujian (jay) wrote:
> 
> 
> > -----Original Message-----
> > From: Michael S. Tsirkin [mailto:mst@redhat.com]
> > Sent: Saturday, March 17, 2018 2:20 AM
> > To: qemu-devel@nongnu.org
> > Cc: Zhoujian (jay) <jianjay.zhou@huawei.com>
> > Subject: [PATCH] vhost-user: avoid misaligned access
> > 
> > We can't pass a pointer to memory field directly since it's within a packed
> > structure, so isn't aligned.
> > Pass a pointer on stack and copy.
> > 
> > Fixes: 30c4cc7 ("vhost: used_memslots refactoring")
> > Cc: Jay Zhou <jianjay.zhou@huawei.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> > 
> > I had to apply this to fix make check errors with clang.
> > Pls review, test and ack.
> > 
> > Thanks!
> > 
> >  hw/virtio/vhost-user.c | 14 +++++++++++---
> >  1 file changed, 11 insertions(+), 3 deletions(-)
> > 
> > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index
> > c12fdd9..a44ee7f 100644
> > --- a/hw/virtio/vhost-user.c
> > +++ b/hw/virtio/vhost-user.c
> > @@ -396,6 +396,7 @@ static int vhost_user_set_mem_table_postcopy(struct
> > vhost_dev *dev,
> >      bool reply_supported = virtio_has_feature(dev->protocol_features,
> > 
> > VHOST_USER_PROTOCOL_F_REPLY_ACK);
> >      VhostUserMsg msg_reply;
> > +    VhostUserMemory memory = {};
> >      int region_i, msg_i;
> > 
> >      VhostUserMsg msg = {
> > @@ -407,10 +408,11 @@ static int vhost_user_set_mem_table_postcopy(struct
> > vhost_dev *dev,
> >          msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
> >      }
> > 
> > -    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
> > +    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
> >          error_report("Failed preparing vhost-user memory table msg");
> >          return -1;
> >      }
> > +    msg.payload.memory = memory;
> > 
> >      fd_num = msg.payload.memory.nregions;
> > 
> > @@ -549,16 +551,19 @@ static int vhost_user_set_mem_table(struct vhost_dev
> > *dev,
> >          .hdr.request = VHOST_USER_SET_MEM_TABLE,
> >          .hdr.flags = VHOST_USER_VERSION,
> >      };
> > +    VhostUserMemory memory = {};
> > 
> >      if (reply_supported) {
> >          msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
> >      }
> > 
> > -    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
> > +    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
> >          error_report("Failed preparing vhost-user memory table msg");
> >          return -1;
> >      }
> > 
> > +    msg.payload.memory = memory;
> > +
> >      fd_num = msg.payload.memory.nregions;
> > 
> >      if (!fd_num) {
> > @@ -1575,8 +1580,11 @@ static void vhost_user_set_used_memslots(struct
> > vhost_dev *dev)  {
> >      int fds[VHOST_MEMORY_MAX_NREGIONS];
> >      VhostUserMsg msg;
> > +    VhostUserMemory memory = {};
> > +
> > +    vhost_user_prepare_msg(dev, &memory, fds);
> > 
> > -    vhost_user_prepare_msg(dev, &msg.payload.memory, fds);
> > +    msg.payload.memory = memory;
> >  }

FYI I think it's better to pass pointer to msg to
avoid alignment issues.

> Hi Michael, here should be like this:
> 
> 
> static void vhost_user_set_used_memslots(struct vhost_dev *dev)
>  {
>      int fds[VHOST_MEMORY_MAX_NREGIONS];
> -    VhostUserMsg msg;
> +    VhostUserMemory memory = {};
>  
> -    vhost_user_prepare_msg(dev, &msg.payload.memory, fds);
> +    vhost_user_prepare_msg(dev, &memory, fds);
>  }
> 
> 
> Regards,
> Jay


But what's the point of all this? The structure is discarded
after being initialized. Doesn't look right to me.

> > 
> >  const VhostOps user_ops = {
> > --
> > MST

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [Qemu-devel] [PATCH] vhost-user: avoid misaligned access
  2018-03-20  2:36   ` Michael S. Tsirkin
@ 2018-03-20  7:05     ` Igor Mammedov
  2018-03-20 11:55       ` Michael S. Tsirkin
  0 siblings, 1 reply; 5+ messages in thread
From: Igor Mammedov @ 2018-03-20  7:05 UTC (permalink / raw)
  To: Michael S. Tsirkin; +Cc: Zhoujian (jay), qemu-devel

On Tue, 20 Mar 2018 04:36:48 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Tue, Mar 20, 2018 at 02:01:07AM +0000, Zhoujian (jay) wrote:
> > 
> >   
> > > -----Original Message-----
> > > From: Michael S. Tsirkin [mailto:mst@redhat.com]
> > > Sent: Saturday, March 17, 2018 2:20 AM
> > > To: qemu-devel@nongnu.org
> > > Cc: Zhoujian (jay) <jianjay.zhou@huawei.com>
> > > Subject: [PATCH] vhost-user: avoid misaligned access
> > > 
> > > We can't pass a pointer to memory field directly since it's within a packed
> > > structure, so isn't aligned.
> > > Pass a pointer on stack and copy.
> > > 
> > > Fixes: 30c4cc7 ("vhost: used_memslots refactoring")
> > > Cc: Jay Zhou <jianjay.zhou@huawei.com>
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > ---
> > > 
> > > I had to apply this to fix make check errors with clang.
> > > Pls review, test and ack.
> > > 
> > > Thanks!
> > > 
> > >  hw/virtio/vhost-user.c | 14 +++++++++++---
> > >  1 file changed, 11 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index
> > > c12fdd9..a44ee7f 100644
> > > --- a/hw/virtio/vhost-user.c
> > > +++ b/hw/virtio/vhost-user.c
> > > @@ -396,6 +396,7 @@ static int vhost_user_set_mem_table_postcopy(struct
> > > vhost_dev *dev,
> > >      bool reply_supported = virtio_has_feature(dev->protocol_features,
> > > 
> > > VHOST_USER_PROTOCOL_F_REPLY_ACK);
> > >      VhostUserMsg msg_reply;
> > > +    VhostUserMemory memory = {};
> > >      int region_i, msg_i;
> > > 
> > >      VhostUserMsg msg = {
> > > @@ -407,10 +408,11 @@ static int vhost_user_set_mem_table_postcopy(struct
> > > vhost_dev *dev,
> > >          msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
> > >      }
> > > 
> > > -    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
> > > +    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
> > >          error_report("Failed preparing vhost-user memory table msg");
> > >          return -1;
> > >      }
> > > +    msg.payload.memory = memory;
> > > 
> > >      fd_num = msg.payload.memory.nregions;
> > > 
> > > @@ -549,16 +551,19 @@ static int vhost_user_set_mem_table(struct vhost_dev
> > > *dev,
> > >          .hdr.request = VHOST_USER_SET_MEM_TABLE,
> > >          .hdr.flags = VHOST_USER_VERSION,
> > >      };
> > > +    VhostUserMemory memory = {};
> > > 
> > >      if (reply_supported) {
> > >          msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
> > >      }
> > > 
> > > -    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
> > > +    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
> > >          error_report("Failed preparing vhost-user memory table msg");
> > >          return -1;
> > >      }
> > > 
> > > +    msg.payload.memory = memory;
> > > +
> > >      fd_num = msg.payload.memory.nregions;
> > > 
> > >      if (!fd_num) {
> > > @@ -1575,8 +1580,11 @@ static void vhost_user_set_used_memslots(struct
> > > vhost_dev *dev)  {
> > >      int fds[VHOST_MEMORY_MAX_NREGIONS];
> > >      VhostUserMsg msg;
> > > +    VhostUserMemory memory = {};
> > > +
> > > +    vhost_user_prepare_msg(dev, &memory, fds);
> > > 
> > > -    vhost_user_prepare_msg(dev, &msg.payload.memory, fds);
> > > +    msg.payload.memory = memory;
> > >  }  
> 
> FYI I think it's better to pass pointer to msg to
> avoid alignment issues.
> 
> > Hi Michael, here should be like this:
> > 
> > 
> > static void vhost_user_set_used_memslots(struct vhost_dev *dev)
> >  {
> >      int fds[VHOST_MEMORY_MAX_NREGIONS];
> > -    VhostUserMsg msg;
> > +    VhostUserMemory memory = {};
> >  
> > -    vhost_user_prepare_msg(dev, &msg.payload.memory, fds);
> > +    vhost_user_prepare_msg(dev, &memory, fds);
> >  }
> > 
> > 
> > Regards,
> > Jay  
> 
> 
> But what's the point of all this? The structure is discarded
> after being initialized. Doesn't look right to me.
I think it was my idea,
point is to share vhost_user_prepare_msg() between
_set_used_memslots and _set_mem_table* instead of
duplicating code, of cause at the cost of discarding
results in vhost_user_set_used_memslots()

> 
> > > 
> > >  const VhostOps user_ops = {
> > > --
> > > MST  
> 

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [Qemu-devel] [PATCH] vhost-user: avoid misaligned access
  2018-03-20  7:05     ` Igor Mammedov
@ 2018-03-20 11:55       ` Michael S. Tsirkin
  0 siblings, 0 replies; 5+ messages in thread
From: Michael S. Tsirkin @ 2018-03-20 11:55 UTC (permalink / raw)
  To: Igor Mammedov; +Cc: Zhoujian (jay), qemu-devel

On Tue, Mar 20, 2018 at 08:05:38AM +0100, Igor Mammedov wrote:
> On Tue, 20 Mar 2018 04:36:48 +0200
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > On Tue, Mar 20, 2018 at 02:01:07AM +0000, Zhoujian (jay) wrote:
> > > 
> > >   
> > > > -----Original Message-----
> > > > From: Michael S. Tsirkin [mailto:mst@redhat.com]
> > > > Sent: Saturday, March 17, 2018 2:20 AM
> > > > To: qemu-devel@nongnu.org
> > > > Cc: Zhoujian (jay) <jianjay.zhou@huawei.com>
> > > > Subject: [PATCH] vhost-user: avoid misaligned access
> > > > 
> > > > We can't pass a pointer to memory field directly since it's within a packed
> > > > structure, so isn't aligned.
> > > > Pass a pointer on stack and copy.
> > > > 
> > > > Fixes: 30c4cc7 ("vhost: used_memslots refactoring")
> > > > Cc: Jay Zhou <jianjay.zhou@huawei.com>
> > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > > > ---
> > > > 
> > > > I had to apply this to fix make check errors with clang.
> > > > Pls review, test and ack.
> > > > 
> > > > Thanks!
> > > > 
> > > >  hw/virtio/vhost-user.c | 14 +++++++++++---
> > > >  1 file changed, 11 insertions(+), 3 deletions(-)
> > > > 
> > > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c index
> > > > c12fdd9..a44ee7f 100644
> > > > --- a/hw/virtio/vhost-user.c
> > > > +++ b/hw/virtio/vhost-user.c
> > > > @@ -396,6 +396,7 @@ static int vhost_user_set_mem_table_postcopy(struct
> > > > vhost_dev *dev,
> > > >      bool reply_supported = virtio_has_feature(dev->protocol_features,
> > > > 
> > > > VHOST_USER_PROTOCOL_F_REPLY_ACK);
> > > >      VhostUserMsg msg_reply;
> > > > +    VhostUserMemory memory = {};
> > > >      int region_i, msg_i;
> > > > 
> > > >      VhostUserMsg msg = {
> > > > @@ -407,10 +408,11 @@ static int vhost_user_set_mem_table_postcopy(struct
> > > > vhost_dev *dev,
> > > >          msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
> > > >      }
> > > > 
> > > > -    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
> > > > +    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
> > > >          error_report("Failed preparing vhost-user memory table msg");
> > > >          return -1;
> > > >      }
> > > > +    msg.payload.memory = memory;
> > > > 
> > > >      fd_num = msg.payload.memory.nregions;
> > > > 
> > > > @@ -549,16 +551,19 @@ static int vhost_user_set_mem_table(struct vhost_dev
> > > > *dev,
> > > >          .hdr.request = VHOST_USER_SET_MEM_TABLE,
> > > >          .hdr.flags = VHOST_USER_VERSION,
> > > >      };
> > > > +    VhostUserMemory memory = {};
> > > > 
> > > >      if (reply_supported) {
> > > >          msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
> > > >      }
> > > > 
> > > > -    if (vhost_user_prepare_msg(dev, &msg.payload.memory, fds) < 0) {
> > > > +    if (vhost_user_prepare_msg(dev, &memory, fds) < 0) {
> > > >          error_report("Failed preparing vhost-user memory table msg");
> > > >          return -1;
> > > >      }
> > > > 
> > > > +    msg.payload.memory = memory;
> > > > +
> > > >      fd_num = msg.payload.memory.nregions;
> > > > 
> > > >      if (!fd_num) {
> > > > @@ -1575,8 +1580,11 @@ static void vhost_user_set_used_memslots(struct
> > > > vhost_dev *dev)  {
> > > >      int fds[VHOST_MEMORY_MAX_NREGIONS];
> > > >      VhostUserMsg msg;
> > > > +    VhostUserMemory memory = {};
> > > > +
> > > > +    vhost_user_prepare_msg(dev, &memory, fds);
> > > > 
> > > > -    vhost_user_prepare_msg(dev, &msg.payload.memory, fds);
> > > > +    msg.payload.memory = memory;
> > > >  }  
> > 
> > FYI I think it's better to pass pointer to msg to
> > avoid alignment issues.
> > 
> > > Hi Michael, here should be like this:
> > > 
> > > 
> > > static void vhost_user_set_used_memslots(struct vhost_dev *dev)
> > >  {
> > >      int fds[VHOST_MEMORY_MAX_NREGIONS];
> > > -    VhostUserMsg msg;
> > > +    VhostUserMemory memory = {};
> > >  
> > > -    vhost_user_prepare_msg(dev, &msg.payload.memory, fds);
> > > +    vhost_user_prepare_msg(dev, &memory, fds);
> > >  }
> > > 
> > > 
> > > Regards,
> > > Jay  
> > 
> > 
> > But what's the point of all this? The structure is discarded
> > after being initialized. Doesn't look right to me.
> I think it was my idea,
> point is to share vhost_user_prepare_msg() between
> _set_used_memslots and _set_mem_table* instead of
> duplicating code, of cause at the cost of discarding
> results in vhost_user_set_used_memslots()

So vhost_user_prepare_msg has a side effect of setting a
global flag, that is why it's called here.
Pls add a comment both near vhost_user_prepare_msg and where
it's called.

> > 
> > > > 
> > > >  const VhostOps user_ops = {
> > > > --
> > > > MST  
> > 

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2018-03-20 11:55 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-03-16 18:20 [Qemu-devel] [PATCH] vhost-user: avoid misaligned access Michael S. Tsirkin
2018-03-20  2:01 ` Zhoujian (jay)
2018-03-20  2:36   ` Michael S. Tsirkin
2018-03-20  7:05     ` Igor Mammedov
2018-03-20 11:55       ` Michael S. Tsirkin

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