Re: [Qemu-devel] [RFC][PATCH 07/16 v6] target-i386: Add API to add extra memory mapping

[Wen Congyang]

At 02/15/2012 01:35 AM, Jan Kiszka Wrote:
> On 2012-02-09 04:24, Wen Congyang wrote:
>> Crash needs extra memory mapping to determine phys_base.
>>
>> Signed-off-by: Wen Congyang <address@hidden>
>> ---
>>  cpu-all.h               |    2 ++
>>  target-i386/arch-dump.c |   43 +++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 45 insertions(+), 0 deletions(-)
>>
>> diff --git a/cpu-all.h b/cpu-all.h
>> index efb5ba3..290c43a 100644
>> --- a/cpu-all.h
>> +++ b/cpu-all.h
>> @@ -530,10 +530,12 @@ int cpu_write_elf64_note(int fd, CPUState *env, int 
>> cpuid,
>>                           target_phys_addr_t *offset);
>>  int cpu_write_elf32_note(int fd, CPUState *env, int cpuid,
>>                           target_phys_addr_t *offset);
>> +int cpu_add_extra_memory_mapping(MemoryMappingList *list);
>>  #else
>>  #define cpu_get_memory_mapping(list, env)
>>  #define cpu_write_elf64_note(fd, env, cpuid, offset) ({ -1; })
>>  #define cpu_write_elf32_note(fd, env, cpuid, offset) ({ -1; })
>> +#define cpu_add_extra_memory_mapping(list) ({ 0; })
>>  #endif
>>  
>>  #endif /* CPU_ALL_H */
>> diff --git a/target-i386/arch-dump.c b/target-i386/arch-dump.c
>> index 4c0ff77..d96f6ae 100644
>> --- a/target-i386/arch-dump.c
>> +++ b/target-i386/arch-dump.c
>> @@ -495,3 +495,46 @@ int cpu_write_elf32_note(int fd, CPUState *env, int 
>> cpuid,
>>  {
>>      return x86_write_elf32_note(fd, env, cpuid, offset);
>>  }
>> +
>> +/* This function is copied from crash */
> 
> And what does it do there and here? I suppose it is Linux-specific - any
> version? This should be documented and encoded in the function name.
> 
>> +static target_ulong get_phys_base_addr(CPUState *env, target_ulong 
>> *base_vaddr)
>> +{
>> +    int i;
>> +    target_ulong kernel_base = -1;
>> +    target_ulong last, mask;
>> +
>> +    for (i = 30, last = -1; (kernel_base == -1) && (i >= 20); i--) {
>> +        mask = ~((1LL << i) - 1);
>> +        *base_vaddr = env->idt.base & mask;
>> +        if (*base_vaddr == last) {
>> +            continue;
>> +        }
>> +
>> +        kernel_base = cpu_get_phys_page_debug(env, *base_vaddr);
>> +        last = *base_vaddr;
>> +    }
>> +
>> +    return kernel_base;
>> +}
>> +
>> +int cpu_add_extra_memory_mapping(MemoryMappingList *list)
> 
> Again, what does "extra" mean? Probably guest-specific, no?

crash will calculate the phys_base according to the virtual address and physical
address stored in the PT_LOAD.

If the vmcore is generated by 'virsh dump'(use migration to implement dumping),
crash calculates the phys_base according to idt.base. The function 
get_phys_base_addr()
uses the same way to calculates the phys_base.

I think crash may work without this. I will verify it.

Thanks
Wen Congyang

> 
>> +{
>> +#ifdef TARGET_X86_64
>> +    target_phys_addr_t kernel_base = -1;
>> +    target_ulong base_vaddr;
>> +    bool lma = !!(first_cpu->hflags & HF_LMA_MASK);
>> +
>> +    if (!lma) {
>> +        return 0;
>> +    }
>> +
>> +    kernel_base = get_phys_base_addr(first_cpu, &base_vaddr);
>> +    if (kernel_base == -1) {
>> +        return -1;
>> +    }
>> +
>> +    create_new_memory_mapping_head(list, kernel_base, base_vaddr,
>> +                                   TARGET_PAGE_SIZE);
>> +#endif
>> +    return 0;
>> +}
> 
> Jan
>