[Qemu-devel] Re: [kvm-devel] [patch 17/24] QEMU/KVM: add cpu_unregister_io_memory and make io mem table index dynamic

[Marcelo Tosatti <marcelo@kvack.org>]

On Tue, Mar 18, 2008 at 06:02:10PM +0530, Amit Shah wrote:
> This patch broke -no-kvm-irqchip:
> 
> * On Wednesday 12 March 2008 01:42:08 Marcelo Tosatti wrote:
> > So drivers can clear their mem io table entries on exit back to unassigned
> > state.
> >
> > Also make the io mem index allocation dynamic.
> >
> > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> >
> > Index: kvm-userspace.hotplug2/qemu/cpu-all.h
> > ===================================================================
> > --- kvm-userspace.hotplug2.orig/qemu/cpu-all.h
> > +++ kvm-userspace.hotplug2/qemu/cpu-all.h
> > @@ -837,6 +837,7 @@ int cpu_register_io_memory(int io_index,
> >                             CPUReadMemoryFunc **mem_read,
> >                             CPUWriteMemoryFunc **mem_write,
> >                             void *opaque);
> > +void cpu_unregister_io_memory(int table_address);
> >  CPUWriteMemoryFunc **cpu_get_io_memory_write(int io_index);
> >  CPUReadMemoryFunc **cpu_get_io_memory_read(int io_index);
> >
> > Index: kvm-userspace.hotplug2/qemu/exec.c
> > ===================================================================
> > --- kvm-userspace.hotplug2.orig/qemu/exec.c
> > +++ kvm-userspace.hotplug2/qemu/exec.c
> > @@ -158,7 +158,7 @@ PhysPageDesc **l1_phys_map;
> >  CPUWriteMemoryFunc *io_mem_write[IO_MEM_NB_ENTRIES][4];
> >  CPUReadMemoryFunc *io_mem_read[IO_MEM_NB_ENTRIES][4];
> >  void *io_mem_opaque[IO_MEM_NB_ENTRIES];
> > -static int io_mem_nb;
> > +char io_mem_used[IO_MEM_NB_ENTRIES];
> >  #if defined(CONFIG_SOFTMMU)
> >  static int io_mem_watch;
> >  #endif
> > @@ -2498,12 +2498,28 @@ static void *subpage_init (target_phys_a
> >      return mmio;
> >  }
> >
> > +static int get_free_io_mem_idx(void)
> > +{
> > +    int i;
> > +
> > +    for (i = 0; i<IO_MEM_NB_ENTRIES; i++)
> > +        if (!io_mem_used[i]) {
> > +            io_mem_used[i] = 1;
> > +            return i;
> > +        }
> > +
> > +    return -1;
> > +}
> > +
> >  static void io_mem_init(void)
> >  {
> > +    int i;
> > +
> >      cpu_register_io_memory(IO_MEM_ROM >> IO_MEM_SHIFT, error_mem_read,
> > unassigned_mem_write, NULL); cpu_register_io_memory(IO_MEM_UNASSIGNED >>
> > IO_MEM_SHIFT, unassigned_mem_read, unassigned_mem_write, NULL);
> > cpu_register_io_memory(IO_MEM_NOTDIRTY >> IO_MEM_SHIFT, error_mem_read,
> > notdirty_mem_write, NULL); -    io_mem_nb = 5;
> > +    for (i=0; i<5; i++)
> > +        io_mem_used[i] = 0;
> 
> The remaining bits (5..IO_MEM_NB_ENTRIES) aren't initialised.
> 
> >
> >  #if defined(CONFIG_SOFTMMU)
> >      io_mem_watch = cpu_register_io_memory(-1, watch_mem_read,
> > @@ -2530,9 +2546,9 @@ int cpu_register_io_memory(int io_index,
> >      int i, subwidth = 0;
> >
> >      if (io_index <= 0) {
> > -        if (io_mem_nb >= IO_MEM_NB_ENTRIES)
> > -            return -1;
> > -        io_index = io_mem_nb++;
> > +        io_index = get_free_io_mem_idx();
> > +        if (io_index == -1)
> > +            return io_index;
> 
> io_mem_nb was initialised to 5 earlier; we now trample over the first 0..4 
> bits.
> 
> This fixes the issue; please check for correctness.
> 
> From: Amit Shah <amit.shah@qumranet.com>
> Date: Tue, 18 Mar 2008 18:01:05 +0530
> Subject: [PATCH] QEMU/KVM: fix initialization of IO memory regions
> 
> Signed-off-by: Amit Shah <amit.shah@qumranet.com>
> ---
>  qemu/exec.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/qemu/exec.c b/qemu/exec.c
> index edeb21a..be15433 100644
> --- a/qemu/exec.c
> +++ b/qemu/exec.c
> @@ -2502,7 +2502,7 @@ static int get_free_io_mem_idx(void)
>  {
>      int i;
>  
> -    for (i = 0; i<IO_MEM_NB_ENTRIES; i++)
> +    for (i = 5; i<IO_MEM_NB_ENTRIES; i++)
>          if (!io_mem_used[i]) {
>              io_mem_used[i] = 1;
>              return i;
> @@ -2518,7 +2518,7 @@ static void io_mem_init(void)
>      cpu_register_io_memory(IO_MEM_ROM >> IO_MEM_SHIFT, error_mem_read, 
> unassigned_mem_write, NULL);
>      cpu_register_io_memory(IO_MEM_UNASSIGNED >> IO_MEM_SHIFT, 
> unassigned_mem_read, unassigned_mem_write, NULL);
>      cpu_register_io_memory(IO_MEM_NOTDIRTY >> IO_MEM_SHIFT, error_mem_read, 
> notdirty_mem_write, NULL);
> -    for (i=0; i<5; i++)
> +    for (i=5; i<IO_MEM_NB_ENTRIES; i++)
>          io_mem_used[i] = 0;
>  
>  #if defined(CONFIG_SOFTMMU)

Hi Amit,

There is no need to zero io_mem_used since its in the BSS. The loop in
io_mem_init() was meant to allocate the slots from 0 to 4, not free
them.

So does the following fix the problem?

diff --git a/qemu/exec.c b/qemu/exec.c
index edeb21a..e5199cf 100644
--- a/qemu/exec.c
+++ b/qemu/exec.c
@@ -2519,7 +2519,7 @@ static void io_mem_init(void)
     cpu_register_io_memory(IO_MEM_UNASSIGNED >> IO_MEM_SHIFT, unassigned_mem_re     cpu_register_io_memory(IO_MEM_NOTDIRTY >> IO_MEM_SHIFT, error_mem_read, not     for (i=0; i<5; i++)
-        io_mem_used[i] = 0;
+        io_mem_used[i] = 1;

 #if defined(CONFIG_SOFTMMU)
     io_mem_watch = cpu_register_io_memory(-1, watch_mem_read,