Oleksandr Tyshchenko <olekst...@gmail.com> writes:
> From: Oleksandr Tyshchenko <oleksandr_tyshche...@epam.com>
>
> As a lot of x86 code can be re-used on Arm later on, this
> patch makes some preparation to x86/hvm/ioreq.c before moving
> to the common code. This way we will get a verbatim copy
<snip>
>
> It worth mentioning that a code which checks the return value of
> p2m_set_ioreq_server() in hvm_map_mem_type_to_ioreq_server() was
> folded into arch_ioreq_server_map_mem_type() for the clear split.
> So the p2m_change_entry_type_global() is called with ioreq_server
> lock held.
<snip>
>
> +/* Called with ioreq_server lock held */
> +int arch_ioreq_server_map_mem_type(struct domain *d,
> + struct hvm_ioreq_server *s,
> + uint32_t flags)
> +{
> + int rc = p2m_set_ioreq_server(d, flags, s);
> +
> + if ( rc == 0 && flags == 0 )
> + {
> + const struct p2m_domain *p2m = p2m_get_hostp2m(d);
> +
> + if ( read_atomic(&p2m->ioreq.entry_count) )
> + p2m_change_entry_type_global(d, p2m_ioreq_server, p2m_ram_rw);
> + }
> +
> + return rc;
> +}
> +
> /*
> * Map or unmap an ioreq server to specific memory type. For now, only
> * HVMMEM_ioreq_server is supported, and in the future new types can be
> @@ -1112,19 +1155,11 @@ int hvm_map_mem_type_to_ioreq_server(struct domain
> *d, ioservid_t id,
> if ( s->emulator != current->domain )
> goto out;
>
> - rc = p2m_set_ioreq_server(d, flags, s);
> + rc = arch_ioreq_server_map_mem_type(d, s, flags);
>
> out:
> spin_unlock_recursive(&d->arch.hvm.ioreq_server.lock);
>
> - if ( rc == 0 && flags == 0 )
> - {
> - struct p2m_domain *p2m = p2m_get_hostp2m(d);
> -
> - if ( read_atomic(&p2m->ioreq.entry_count) )
> - p2m_change_entry_type_global(d, p2m_ioreq_server, p2m_ram_rw);
> - }
> -
It should be noted that p2m holds it's own lock but I'm unfamiliar with
Xen's locking architecture. Is there anything that prevents another vCPU
accessing a page that is also being used my ioreq on the first vCPU?
Assuming that deadlock isn't a possibility to my relatively untrained
eye this looks good to me:
Reviewed-by: Alex Bennée <alex.ben...@linaro.org>
--
Alex Bennée
