[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [v5][PATCH 10/16] tools: introduce some new parameters to set rdm policy

Global RDM parameter, "type", allows user to specify reserved regions
explicitly, e.g. using 'host' to include all reserved regions reported

As I understand this feature, I don't think the name `type' is right.
This is a method for handling or overriding/ignoring the RDM problem.

Perhaps `handling=' or `strategy=' ?

Okay, I prefer to use 'strategy='.

And `none' seems quite an innocuous name for such a dangerous
setting.  How about `ignore' ?

'strict/relaxed' policy decides how to handle conflict when reserving RDM
regions in pfn space. If conflict exists, 'strict' means an immediate error
so VM can't keep running, while 'relaxed' allows moving forward with a
warning message thrown out.

Default per-device RDM policy is 'strict', while default global RDM policy
is 'relaxed'. And the per-device policy would override the global policy like

I don't think these two sentences can both be true.  If the per-device
policy overrides the global policy, then the per-device policy must
have at least three values: `strict', `relaxed', and `not set'
(implicitly using global policy).

Yeah. The per-device policy is first set as the global policy. This behavior is same as other pci option. Please see the last patch,

@@ -1937,6 +1945,11 @@ skip_vfb:
             pcidev->power_mgmt = pci_power_mgmt;
             pcidev->permissive = pci_permissive;
             pcidev->seize = pci_seize;
+            /*
+             * Like other pci option, the per-device policy always follows
+             * the global policy by default.
+             */
+            pcidev->rdm_reserve = b_info->u.hvm.rdm.reserve;
             if (!xlu_pci_parse_bdf(config, pcidev, buf))

Perhaps I have misunderstood.

diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index a3e0e2e..a2dc343 100644
--- a/docs/man/xl.cfg.pod.5
+++ b/docs/man/xl.cfg.pod.5
@@ -655,6 +655,83 @@ assigned slave device.
+=item B<type="STRING">

The documentation on this is rather vague about what the default is.
But you do say:

+In this conflict case,
+#1. If the type options is set with "none",
+rdm = "type=none,reserve=strict" or rdm = "type=none,reserve=relaxed"
+mean we don't handle any conflict just to make VM keep running as before.
+Note this is our default behavior.

This suggests that the default is "do the dangerous thing".  That
doesn't seem right.

As I discussed with Campbell we'd like not to expose "none" in xl level since this is equivalent to that case we don't set anything.

+#2. If the type options is set with "host",
+rdm = "type=host,reserve=strict" or rdm = "type=host,reserve=relaxed"
+"relaxed" allows a VM to be created to keep running with a warning message
+thrown out. But this may crash this VM if this device accesses RDM. For 
+Windows IGD GFX driver always access these regions so this lead to a blue 
+to crash VM in such a case.

The difference between
is simply whether a warning is printed ?

"none" means we have a chance to work as before since not all devices own RDM. But as I said above this is same as !rdm.


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.