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

Glauber Costa
2008-09-10T14:52:39Z

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."