static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages)
{
unsigned int clobber;
copy_in_guest_info(cpu, pages);
cpu->regs->trapnum = 256;
asm volatile("pushf; lcall *lguest_entry"
: "=a"(clobber), "=b"(clobber)
: "0"(pages), "1"(__pa(cpu->lg->pgdirs[cpu->cpu_pgd].pgdir))
: "memory", "%edx", "%ecx", "%edi", "%esi");
}
/* Finally: the code to actually call into the Switcher to run the Guest. */
static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages)
{
/* This is a dummy value we need for GCC's sake. */
unsigned int clobber;
/*
* Copy the guest-specific information into this CPU's "struct
* lguest_pages".
*/
copy_in_guest_info(cpu, pages);
/*
* Set the trap number to 256 (impossible value). If we fault while
* switching to the Guest (bad segment registers or bug), this will
* cause us to abort the Guest.
*/
cpu->regs->trapnum = 256;
/*
* Now: we push the "eflags" register on the stack, then do an "lcall".
* This is how we change from using the kernel code segment to using
* the dedicated lguest code segment, as well as jumping into the
* Switcher.
*
* The lcall also pushes the old code segment (KERNEL_CS) onto the
* stack, then the address of this call. This stack layout happens to
* exactly match the stack layout created by an interrupt...
*/
asm volatile("pushf; lcall *%4"
/*
* This is how we tell GCC that %eax ("a") and %ebx ("b")
* are changed by this routine. The "=" means output.
*/
: "=a"(clobber), "=b"(clobber)
/*
* %eax contains the pages pointer. ("0" refers to the
* 0-th argument above, ie "a"). %ebx contains the
* physical address of the Guest's top-level page
* directory.
*/
: "0"(pages),
"1"(__pa(cpu->lg->pgdirs[cpu->cpu_pgd].pgdir)),
"m"(lguest_entry)
/*
* We tell gcc that all these registers could change,
* which means we don't have to save and restore them in
* the Switcher.
*/
: "memory", "%edx", "%ecx", "%edi", "%esi");
}
