Re: [Qemu-devel] [PATCH 4/10] Add dirty tracking for live migration

["Glauber Costa" <glommer@gmail.com>]

On Tue, Sep 9, 2008 at 4:49 PM, Anthony Liguori <aliguori@us.ibm.com> wrote:
> This patch adds a dirty tracking bit for live migration.  We use 0x08 because
> kqemu uses 0x04.

For which purpose, and where is it? I think it deserves at least a
comment on the source itself for future generations.

>
> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
>
> diff --git a/cpu-all.h b/cpu-all.h
> index d350b30..fdac353 100644
> --- a/cpu-all.h
> +++ b/cpu-all.h
> @@ -944,6 +944,7 @@ int cpu_memory_rw_debug(CPUState *env, target_ulong addr,
>
>  #define VGA_DIRTY_FLAG  0x01
>  #define CODE_DIRTY_FLAG 0x02
> +#define MIGRATION_DIRTY_FLAG 0x08
>
>  /* read dirty bit (return 0 or 1) */
>  static inline int cpu_physical_memory_is_dirty(ram_addr_t addr)
> @@ -966,6 +967,10 @@ void cpu_physical_memory_reset_dirty(ram_addr_t start, ram_addr_t end,
>                                      int dirty_flags);
>  void cpu_tlb_update_dirty(CPUState *env);
>
> +int cpu_physical_memory_set_dirty_tracking(int enable);
> +
> +int cpu_physical_memory_get_dirty_tracking(void);
> +
>  void dump_exec_info(FILE *f,
>                     int (*cpu_fprintf)(FILE *f, const char *fmt, ...));
>
> diff --git a/exec.c b/exec.c
> index 3ab4ad0..9dba5c8 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -38,6 +38,7 @@
>  #include "qemu-common.h"
>  #include "tcg.h"
>  #include "hw/hw.h"
> +#include "osdep.h"
>  #if defined(CONFIG_USER_ONLY)
>  #include <qemu.h>
>  #endif
> @@ -113,6 +114,7 @@ ram_addr_t phys_ram_size;
>  int phys_ram_fd;
>  uint8_t *phys_ram_base;
>  uint8_t *phys_ram_dirty;
> +static int in_migration;
>  static ram_addr_t phys_ram_alloc_offset = 0;
>  #endif
>
> @@ -1777,6 +1779,17 @@ void cpu_physical_memory_reset_dirty(ram_addr_t start, ram_addr_t end,
>     }
>  }
>
> +int cpu_physical_memory_set_dirty_tracking(int enable)
> +{
> +    in_migration = enable;
> +    return 0;
> +}
> +
> +int cpu_physical_memory_get_dirty_tracking(void)
> +{
> +    return in_migration;
> +}
> +
>  static inline void tlb_update_dirty(CPUTLBEntry *tlb_entry)
>  {
>     ram_addr_t ram_addr;
> @@ -2932,9 +2945,19 @@ void stl_phys_notdirty(target_phys_addr_t addr, uint32_t val)
>         io_index = (pd >> IO_MEM_SHIFT) & (IO_MEM_NB_ENTRIES - 1);
>         io_mem_write[io_index][2](io_mem_opaque[io_index], addr, val);
>     } else {
> -        ptr = phys_ram_base + (pd & TARGET_PAGE_MASK) +
> -            (addr & ~TARGET_PAGE_MASK);
> +        unsigned long addr1 = (pd & TARGET_PAGE_MASK) + (addr & ~TARGET_PAGE_MASK);
> +        ptr = phys_ram_base + addr1;
>         stl_p(ptr, val);
> +
> +        if (unlikely(in_migration)) {
> +            if (!cpu_physical_memory_is_dirty(addr1)) {
> +                /* invalidate code */
> +                tb_invalidate_phys_page_range(addr1, addr1 + 4, 0);
> +                /* set dirty bit */
> +                phys_ram_dirty[addr1 >> TARGET_PAGE_BITS] |=
> +                    (0xff & ~CODE_DIRTY_FLAG);
> +            }
> +        }
>     }
>  }
did you mean MIGRATION_DIRTY_FLAG?

-- 
Glauber Costa.
"Free as in Freedom"
http://glommer.net

"The less confident you are, the more serious you have to act."