qemu-system-amd64 and freebsd guest

[Juergen Lock]

On Sat, Feb 16, 2008 at 06:43:31PM +0200, Kostik Belousov wrote:
> My recent attempts to boot CURRENT amd64 on QEMU 0.9.1 resulted in the
> consistent kernel panic in the first instruction of the root_bus_ocnfigure()
> function. Looking around, I noted that this instruction is the second one
> executed after "sti" in the amd64/amd64/autoconf.c:configure().
> CPU executes
> 	sti
> 	call root_bus_configure
> 	pushq %rbp <- General Protection Fault there
> 
> It makes me suspect that fault happen when hardware interrupt is delivered.
> Indeed, looking around qemu source code and setting breakpoints in QEMU,
> I noted that hw interrupt is delivered, with into = -1. Calculation of
> the IDT index in the QEMU' target-i386/helper.c:do_interrupt64() as
> intno*16 and comparision with unsigned limit looked as overflow and GPF
> was delivered instead.
> 
> Then, it appears that -1 comes from cpu_get_pic_interrupt() when
> apic_accept_pic_intr() returns false. This happen, in particular, when
> corresponding lapic vector is masked. The situation is legitimate, and
> I think that QEMU shall not deliver an interrupt in this case.
> 
> The following patch allows me to boot the amd64 freebsd on qemu 0.9.1
> from ports.
> 
> --- cpu-exec.c.orig	2008-02-16 18:23:53.134009488 +0200
> +++ cpu-exec.c	2008-02-16 18:24:47.127662872 +0200
> @@ -452,13 +452,15 @@
>                          svm_check_intercept(SVM_EXIT_INTR);
>                          env->interrupt_request &= ~(CPU_INTERRUPT_HARD | CPU_INTERRUPT_VIRQ);
>                          intno = cpu_get_pic_interrupt(env);
> -                        if (loglevel & CPU_LOG_TB_IN_ASM) {
> -                            fprintf(logfile, "Servicing hardware INT=0x%02x\n", intno);
> -                        }
> -                        do_interrupt(intno, 0, 0, 0, 1);
> -                        /* ensure that no TB jump will be modified as
> -                           the program flow was changed */
> -                        BREAK_CHAIN;
> +			if (intno != -1) {
> +				if (loglevel & CPU_LOG_TB_IN_ASM) {
> +				    fprintf(logfile, "Servicing hardware INT=0x%02x\n", intno);
> +				}
> +				do_interrupt(intno, 0, 0, 0, 1);
> +				/* ensure that no TB jump will be modified as
> +				   the program flow was changed */
> +				BREAK_CHAIN;
> +			}
>  #if !defined(CONFIG_USER_ONLY)
>                      } else if ((interrupt_request & CPU_INTERRUPT_VIRQ) &&
>                          (env->eflags & IF_MASK) && !(env->hflags & HF_INHIBIT_IRQ_MASK)) {

Hey, thanks for looking at this one! :)  Maybe you should post the patch
on the qemu list so the right ppl can look at it, and see if it is correct:
	http://lists.gnu.org/mailman/listinfo/qemu-devel

 Thanx,
	Juergen