Re: KVM_MEM_READONLY slot flag not working properly

[Paolo Bonzini]

On 18/03/21 18:40, Lorenzo Susini wrote:
> Well I'm sorry but I didn't know IDT was marked as read only by
> Linux. If it is read only, how can you register any new interrupt
> handler? I guess it's a way of securing stuff against malicious
> attacks. I was taking for granted that the IDT was written when
> registering a new irq handler, given that when an interrupt is
> raised, the new specified handler has to be called and its address
> should be retrieved in some way, that is by storing it in the IDT.

There's a list of handlers for each IDT entry.  This is because the  IDT 
entrypoint has to do more stuff before and after calling the function 
(and also it has to return with IRET instead of RET).  So the IDT entry 
does not point directly to the function that you register.

(Also some interrupts may be shared by multiple devices, in which case 
you can have more than one handler).

> I'm sorry, I'm a student and I'm trying to understand things, Thank
> you, Lorenzo

No problem. :)

Paolo