[Qemu-devel] Re: [Bochs-developers] [PATCH 5/6] Don't use unreserved memory in BIOS.

[Gleb Natapov]

On Fri, Oct 31, 2008 at 12:12:00AM +0100, Sebastian Herbszt wrote:
> Gleb Natapov wrote:
>
>> Use only first page and last page of low memory. OSes assumes that first
>> page is used by bios and last page is reserved in e820 map.
>>
>> Signed-off-by: Gleb Natapov <address@hidden>
>> ---
>>
>> bios/rombios.c   |    6 +++---
>> bios/rombios.h   |    2 +-
>> bios/rombios32.c |    2 +-
>> 3 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/bios/rombios.c b/bios/rombios.c
>> index c4c1e35..19f0e93 100644
>> --- a/bios/rombios.c
>> +++ b/bios/rombios.c
>> @@ -4541,7 +4541,7 @@ ASM_END
>>                 {
>>                     case 0:
>>                         set_e820_range(ES, regs.u.r16.di,
>> -                                       0x0000000L, 0x0009fc00L, 1);
>> +                                       0x0000000L, 0x0009f000L, 1);
>>                         regs.u.r32.ebx = 1;
>>                         regs.u.r32.eax = 0x534D4150;
>>                         regs.u.r32.ecx = 0x14;
>> @@ -4550,7 +4550,7 @@ ASM_END
>>                         break;
>>                     case 1:
>>                         set_e820_range(ES, regs.u.r16.di,
>> -                                       0x0009fc00L, 0x000a0000L, 2);
>> +                                       0x0009f000L, 0x000a0000L, 2);
>>                         regs.u.r32.ebx = 2;
>>                         regs.u.r32.eax = 0x534D4150;
>>                         regs.u.r32.ecx = 0x14;
>> @@ -10021,7 +10021,7 @@ rombios32_05:
>>   cld
>>
>>   ;; init the stack pointer
>> -  mov esp, #0x00080000
>> +  mov esp, #0x9fbf0
>>
>>   ;; pass pointer to s3_resume_flag and s3_resume_vector to rombios32
>>   push #0x04b0
>> diff --git a/bios/rombios.h b/bios/rombios.h
>> index f0ed88e..57b0f46 100644
>> --- a/bios/rombios.h
>> +++ b/bios/rombios.h
>> @@ -56,7 +56,7 @@
>> #define ACPI_DATA_SIZE    0x00010000L
>> #define PM_IO_BASE        0xb000
>> #define SMB_IO_BASE       0xb100
>> -#define CPU_COUNT_ADDR    0xf000
>> +#define CPU_COUNT_ADDR    0x0500
>
> Why did you pick 0x500?
>
Cool number, don't you think so? It is unused location in a first page.
if 0x666 is unused we can use it instead.

--
                        Gleb.