Re: mmap local APIC address

[Vaibhav Jain <vjoss197@xxxxxxxxx>]

On Wed, Oct 19, 2011 at 11:02 AM, Vaibhav Jain <vjoss197@xxxxxxxxx> wrote:

On Wed, Oct 19, 2011 at 10:57 AM, bob <ilikepie420@xxxxxxxx> wrote:

It would be nice to share your solution in case someone else comes into the same problem.

Hi,

It was stupid mistake. I forgot to initialize the file descriptor which was passed to  mmap and therefore it was throwing "Bad file descriptor" error.i realized it after looking the errors in "man mmap".

Thanks
Vaibhav Jain

 

 

Hi,

 

I am now having another problem with the code. It throws a segmentation fault as soon as it tries to write something into the ICR of the APIC.(line highlighted below).

Is is not possible to do this through a user-level program ?

 

 

Here's the code

 

typedef unsigned int u32;

#define MAP_LEN                 0x1000  //4 KB page
#define BUFLEN 100
#define APIC_BASE               0xfee00000
#define APIC_ICR_low            0xfee00300
#define APIC_ICR_high           0xfee00310
#define APIC_ICR_init           0x00000500
#define APIC_ICR_start          0x00000600
#define APIC_ICR_ASSERT_LVL_TRG 0x0000c000
#define BOUNCE_CODE        0x2000

int apic_reset_cpu(cpu);
int cpu = 2;

int main(){
if ((apic_reset_cpu(cpu)) != 0)
    printf("INIT & Startup failed!\n");
}

int apic_reset_cpu(int cpu)
{
  unsigned long tmpaddress, apic_icr, *apic_phy_addr;
  int fd, sleep_now=0;

  printf("Assuming APIC physical base: %lx \n", APIC_BASE);
  tmpaddress = (unsigned long) mmap(NULL, MAP_LEN, PROT_READ|PROT_WRITE, MAP_SHARED, fd, (off_t)APIC_BASE);
 
  if(tmpaddress == (unsigned long)MAP_FAILED) //check if it worked
  {
    perror("Mapping memory for absolute memory access failed.\n");
    return -3;
  }
 
  //prep ICR high
  apic_icr = tmpaddress;
  apic_icr |= APIC_ICR_high;
  apic_phy_addr = (unsigned long *) apic_icr;
  *apic_phy_addr = cpu << 24;
 
  //prep ICR low Send INIT and wait
  apic_icr = tmpaddress;
  apic_icr |= APIC_ICR_low;
  apic_phy_addr = (unsigned long *) apic_icr;
  *apic_phy_addr = APIC_ICR_init | APIC_ICR_ASSERT_LVL_TRG;
  sleep_now = usleep( 10000 ); //sleep 10 ms

  //prep for SIPI
  apic_icr = tmpaddress;
  apic_icr |= APIC_ICR_low;
  apic_phy_addr = (unsigned long *) apic_icr;
  *apic_phy_addr = APIC_ICR_start | (BOUNCE_CODE >> 12);
  sleep_now = usleep( 500 ); //sleep 500 usec

  printf("Unmapping APIC Base page\n");
  tmpaddress &= 0xfffff000;
  munmap(tmpaddress, MAP_LEN); 
 
  return 0;
}

 

 

Thanks

Vaibhav Jain

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