Hi ,
> On 13 Jul 2022, at 1:29 pm, Julien Grall <jul...@xen.org> wrote:
>
>
>
> On 13/07/2022 13:12, Bertrand Marquis wrote:
>>> On 13 Jul 2022, at 12:31, Julien Grall <jul...@xen.org> wrote:
>>>> I can't
>>>> see why it would be wrong to have a more tight limit on static ports
>>>> than on traditional ("dynamic") ones. Even if only to make sure so
>>>> many dynamic ones are left.
>>>
>>> This is similar to Xen forbidding to close a static port: it is not the
>>> hypervisor business to check that there are enough event channel ports
>>> freed for dynamic allocation.
>> On other side we need to be cautious not to add too much complexity in the
>> code by trying to make things always magically work.
>> If you want Xen to be accessible to non expert by magically working all the
>> time, there would be a lot of work to do.
>
> It is not clear to me whether you are referring to a developper or admin here.
>
> On the admin side, we need to make sure they have an easy way to configure
> event channels. One knob is always going to easier than two knobs.
>
> On the developper side, this could be resolved by better documentation in the
> code/interface.
>
> Cheers,
To conclude the discussion, If everyone agree I will add the below patch or
similar in the next version to restrict the
max number of evtchn supported as suggested.
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 532e50e321..a8c5825a4f 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -3422,7 +3422,7 @@ void __init create_domUs(void)
struct xen_domctl_createdomain d_cfg = {
.arch.gic_version = XEN_DOMCTL_CONFIG_GIC_NATIVE,
.flags = XEN_DOMCTL_CDF_hvm | XEN_DOMCTL_CDF_hap,
- .max_evtchn_port = -1,
+ .max_evtchn_port = MAX_EVTCHNS_PORT,
.max_grant_frames = -1,
.max_maptrack_frames = -1,
.grant_opts = XEN_DOMCTL_GRANT_version(opt_gnttab_max_version),
@@ -3582,7 +3582,7 @@ void __init create_dom0(void)
struct domain *dom0;
struct xen_domctl_createdomain dom0_cfg = {
.flags = XEN_DOMCTL_CDF_hvm | XEN_DOMCTL_CDF_hap,
- .max_evtchn_port = -1,
+ .max_evtchn_port = MAX_EVTCHNS_PORT,
.max_grant_frames = gnttab_dom0_frames(),
.max_maptrack_frames = -1,
.grant_opts = XEN_DOMCTL_GRANT_version(opt_gnttab_max_version),
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index f08b07b8de..b1f95fbe1a 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -763,7 +763,7 @@ static struct domain *__init create_dom0(const module_t
*image,
{
struct xen_domctl_createdomain dom0_cfg = {
.flags = IS_ENABLED(CONFIG_TBOOT) ? XEN_DOMCTL_CDF_s3_integrity : 0,
- .max_evtchn_port = -1,
+ .max_evtchn_port = MAX_EVTCHNS_PORT,
.max_grant_frames = -1,
.max_maptrack_frames = -1,
.grant_opts = XEN_DOMCTL_GRANT_version(opt_gnttab_max_version),
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index d6c029020f..783359f733 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -76,6 +76,8 @@ extern domid_t hardware_domid;
/* Maximum number of event channels for any ABI. */
#define MAX_NR_EVTCHNS MAX(EVTCHN_2L_NR_CHANNELS, EVTCHN_FIFO_NR_CHANNELS)
+#define MAX_EVTCHNS_PORT 4096
+
#define EVTCHNS_PER_BUCKET (PAGE_SIZE / next_power_of_2(sizeof(struct evtchn)))
#define EVTCHNS_PER_GROUP (BUCKETS_PER_GROUP * EVTCHNS_PER_BUCKET)
#define NR_EVTCHN_GROUPS DIV_ROUND_UP(MAX_NR_EVTCHNS, EVTCHNS_PER_GROUP
Regards,
Rahul
