2012/10/17 Philipp Eppelt philipp.eppelt@mailbox.tu-dresden.de:

On 10/16/2012 02:04 PM, Ildar Ismagilov wrote:

...

In function l4vcpu_irq_restore on l4/pkg/libvcpu/include/vcpu.h file:

L4_CV L4_INLINE void l4vcpu_irq_restore(l4_vcpu_state_t *vcpu, l4vcpu_irq_state_t s, l4_utcb_t *utcb, l4vcpu_event_hndl_t do_event_work_cb, l4vcpu_setup_ipc_t setup_ipc) L4_NOTHROW { if (s & L4_VCPU_F_IRQ) l4vcpu_irq_enable(vcpu, utcb, do_event_work_cb, setup_ipc); }

why don't call l4vcpu_irq_disable(vcpu) if "s" variable don't include L4_VCPU_F_IRQ flag?

possible should be so:

L4_CV L4_INLINE void l4vcpu_irq_restore(l4_vcpu_state_t *vcpu, l4vcpu_irq_state_t s, l4_utcb_t *utcb, l4vcpu_event_hndl_t do_event_work_cb, l4vcpu_setup_ipc_t setup_ipc) L4_NOTHROW { if (s & L4_VCPU_F_IRQ) l4vcpu_irq_enable(vcpu, utcb, do_event_work_cb, setup_ipc); else l4vcpu_irq_disable(vcpu); }

Hi Ildar,

your way of writing it is also valid, but that would be an unnecesseary call. Here is why: You can only get a (valid) state to restore by a call to l4vcpu_irq_disable_save, so IRQs in your vcpu are disabled.

When you now call l4vcpu_irq_restore and you want to restore a state with disabled IRQs, you don't need to change anything. If you want to restore a state with enabled IRQs, then IRQs get enabled.

Regards, Philipp

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found bug in genode block driver for L4Linux. Below you can find description of the bug in a pseudo code:

unsigned long flag1; unsigned long flag2;

flag1 = l4vcpu_irq_disable_save(...); // irq is DISABLED flag2 = l4vcpu_irq_disable_save(...); // irq is DISABLED ... l4vcpu_irq_enable(...); // irq is ENABLED ... // BUG: not called l4vcpu_irq_disable function! l4vcpu_irq_restore(flag2); // irq is ENABLED but should be DISABLED!!! l4vcpu_irq_restore(flag1);

Should two function l4vcpu_irq_disable_save and l4vcpu_irq_restore guarantee equal irq state before l4vcpu_irq_disable_save and after l4vcpu_irq_restore functions? Maybe an assert in l4vcpu_irq_restore function for bug checking should be added? Or maybe debug print and l4vcpu_irq_disable(vcpu) function call should be added?