Re: [Qemu-devel] [PATCH v6 4/6] Add support for marking memory to not be migrated. On migration, memory is checked for the NO_MIGRATION_FLAG.

[Cam Macdonell]

On Mon, Jun 14, 2010 at 9:51 AM, Anthony Liguori <address@hidden> wrote:
> On 06/04/2010 04:45 PM, Cam Macdonell wrote:
>>
>> This is useful for devices that do not want to take memory regions data
>> with them on migration.
>> ---
>>  arch_init.c  |   28 ++++++++++++++++------------
>>  cpu-all.h    |    2 ++
>>  cpu-common.h |    2 ++
>>  exec.c       |   12 ++++++++++++
>>  4 files changed, 32 insertions(+), 12 deletions(-)
>>
>> diff --git a/arch_init.c b/arch_init.c
>> index cfc03ea..7a234fa 100644
>> --- a/arch_init.c
>> +++ b/arch_init.c
>> @@ -118,18 +118,21 @@ static int ram_save_block(QEMUFile *f)
>>                                              current_addr +
>> TARGET_PAGE_SIZE,
>>                                              MIGRATION_DIRTY_FLAG);
>>
>> -            p = qemu_get_ram_ptr(current_addr);
>> -
>> -            if (is_dup_page(p, *p)) {
>> -                qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_COMPRESS);
>> -                qemu_put_byte(f, *p);
>> -            } else {
>> -                qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_PAGE);
>> -                qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
>> -            }
>> +            if (!cpu_physical_memory_get_dirty(current_addr,
>> +                                                    NO_MIGRATION_FLAG)) {
>> +                p = qemu_get_ram_ptr(current_addr);
>> +
>> +                if (is_dup_page(p, *p)) {
>> +                    qemu_put_be64(f, current_addr |
>> RAM_SAVE_FLAG_COMPRESS);
>> +                    qemu_put_byte(f, *p);
>> +                } else {
>> +                    qemu_put_be64(f, current_addr | RAM_SAVE_FLAG_PAGE);
>> +                    qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
>> +                }
>>
>> -            found = 1;
>> -            break;
>> +                found = 1;
>> +                break;
>> +            }
>>          }
>>
>
> Shouldn't we just disable live migration out right?

I'm confused, as you seemed insistent on migration before.  Do you
want to support static migration (suspend/resume), but not live
migration?  What information do the master/peer roles represent then?

>
> I would rather that the device mark migration as impossible having the user
> hot remove the device before migration and then add it again after
> migration.  Device assignment could also use this functionality.

Would marking migration impossible be a new mechanism or are there
other devices that mark migration impossible? or something added to
QMP "Sorry, you can't migrate with device 'x' attached"?

Cam

>>          addr += TARGET_PAGE_SIZE;
>>          current_addr = (saved_addr + addr) % last_ram_offset;
>> @@ -146,7 +149,8 @@ static ram_addr_t ram_save_remaining(void)
>>      ram_addr_t count = 0;
>>
>>      for (addr = 0; addr<  last_ram_offset; addr += TARGET_PAGE_SIZE) {
>> -        if (cpu_physical_memory_get_dirty(addr, MIGRATION_DIRTY_FLAG)) {
>> +        if (!cpu_physical_memory_get_dirty(addr, NO_MIGRATION_FLAG)&&
>> +                cpu_physical_memory_get_dirty(addr,
>> MIGRATION_DIRTY_FLAG)) {
>>              count++;
>>          }
>>      }
>> diff --git a/cpu-all.h b/cpu-all.h
>> index 9080cc7..4df00ab 100644
>> --- a/cpu-all.h
>> +++ b/cpu-all.h
>> @@ -887,6 +887,8 @@ extern int mem_prealloc;
>>  #define CODE_DIRTY_FLAG      0x02
>>  #define MIGRATION_DIRTY_FLAG 0x08
>>
>> +#define NO_MIGRATION_FLAG 0x10
>> +
>>  #define DIRTY_ALL_FLAG  (VGA_DIRTY_FLAG | CODE_DIRTY_FLAG |
>> MIGRATION_DIRTY_FLAG)
>>
>>  /* read dirty bit (return 0 or 1) */
>> diff --git a/cpu-common.h b/cpu-common.h
>> index 4b0ba60..a1ebbbe 100644
>> --- a/cpu-common.h
>> +++ b/cpu-common.h
>> @@ -39,6 +39,8 @@ static inline void
>> cpu_register_physical_memory(target_phys_addr_t start_addr,
>>      cpu_register_physical_memory_offset(start_addr, size, phys_offset,
>> 0);
>>  }
>>
>> +void cpu_mark_pages_no_migrate(ram_addr_t start, uint64_t size);
>> +
>>  ram_addr_t cpu_get_physical_page_desc(target_phys_addr_t addr);
>>  ram_addr_t qemu_ram_map(ram_addr_t size, void *host);
>>  ram_addr_t qemu_ram_alloc(ram_addr_t);
>> diff --git a/exec.c b/exec.c
>> index 39c18a7..c11d22f 100644
>> --- a/exec.c
>> +++ b/exec.c
>> @@ -2786,6 +2786,18 @@ static void *file_ram_alloc(ram_addr_t memory,
>> const char *path)
>>  }
>>  #endif
>>
>> +void cpu_mark_pages_no_migrate(ram_addr_t start, uint64_t length)
>> +{
>> +    int i, len;
>> +    uint8_t *p;
>> +
>> +    len = length>>  TARGET_PAGE_BITS;
>> +    p = phys_ram_flags + (start>>  TARGET_PAGE_BITS);
>> +    for (i = 0; i<  len; i++) {
>> +        p[i] |= NO_MIGRATION_FLAG;
>> +    }
>> +}
>> +
>>  ram_addr_t qemu_ram_map(ram_addr_t size, void *host)
>>  {
>>      RAMBlock *new_block;
>>
>
>