I guessed the cause of the error is really somewhere else - nothing to do with this part. But without a full view of the entire source - it is hard to diagnose the bugs. (Perhaps even more difficult if full view is available). But I have no problem insmod lg.ko in drivers/lguest directory (after CONFIG_LGUEST is set to "m"), and lguest is not a simple example I must say. And to get a better understanding on how to use the kvm_hypercall APIs, just go to the kernel source's drivers/lguest directory and enter "make" and it will churns lots of information (totalling about 7000+ lines) teaching you the basic of KVM - both how the KVM hypervisor works, and how the lguest work. And if u are lazy to do a "make" this is my version: https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B1hg6_Fvn... On Thu, Jun 9, 2011 at 4:35 PM, emilie lefebvre <tricheurs@hotmail.fr> wrote:
Hi, I try this :
local_irq_save(flags); kvm_hypercall2 ( 6, 2, 2); local_irq_restore(flags);
But I still have my kernel panic with "divide error: 0000 [#1] SMP" that I don't understand! with or without lock, nothing change, the same when I change the current state.
I tried to move my hypercall and I still don't understand why it works just before my test "if (piga_on == 1)" without any protections (like disable interrupts) and not after..
Thank you for trying to help me
Date: Thu, 9 Jun 2011 09:46:12 +0800 Subject: Re: Problems with hypercalls From: htmldeveloper@gmail.com To: tricheurs@hotmail.fr CC: kernelnewbies@kernelnewbies.org
perhaps this example will provide u with more info:
http://a380.informatik.uni-bremen.de/lxr/source/arch/x86/lguest/boot.c
I think the correct step is to disable IRQ instead - before every call to kvm_hypercallX(). The reason is given in the remark:
110 /* 111 * Disable interrupts if not already disabled: we don't want an 112 * interrupt handler making a hypercall while we're already doing 113 * one! 114 */
On Wed, Jun 8, 2011 at 10:54 PM, emilie lefebvre <tricheurs@hotmail.fr> wrote:
This is my function :
static spinlock_t xgr_learn_lock = SPIN_LOCK_UNLOCKED; static int piga_seq_cpt = 1;
/* * Function called for each systemcall (Hook SELinux avc function) */ int piga_control(u32 ssid, ...., struct av_decision * avd) {
/* * Here my hypercall work but block my vm with this error : * " BUG: scheduling while atomic ... " */
spin_lock_bh(&xgr_learn_lock); if ( in_atomic()) kvm_hypercall2 ( 6, (unsigned long)2 ,(unsigned long)piga_seq_cpt); spin_unlock_bh(&xgr_learn_lock);
if (piga_on == 1) { /* * Here my hypercall make a kernel panic with this error: * " divide error: 0000 [#1] SMP" */ spin_lock_bh(&xgr_learn_lock); set_current_state(TASK_UNINTERRUPTIBLE); kvm_hypercall2 ( 6, (unsigned long)2 ,(unsigned long)piga_seq_cpt); set_current_state(TASK_RUNNING); spin_lock_bh(&xgr_learn_lock); } }
I think u generally set TASK_UNINTERRUPTIBLE whenever about to modify the scheduling task list (eg, wait queue manipulation) or about to call "schedule()" (ie, doing your own scheduling). The function set_current_state() literally just set the variable value only, it does not disable interrupt.
-- Regards, Peter Teoh
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-- Regards, Peter Teoh