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Re: [Xen-devel] [PATCH 02/18] xen/arm: Implement PSCI system suspend call (virtual interface)

On 11/13/2018 09:32 AM, Andrew Cooper wrote:
On 12/11/2018 19:56, Julien Grall wrote:
Hi Andrew,

On 11/12/18 4:41 PM, Andrew Cooper wrote:
On 12/11/18 16:35, Mirela Simonovic wrote:
diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index e594b48d81..7f8105465c 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -97,6 +97,11 @@ static void ctxt_switch_from(struct vcpu *p)
        if ( is_idle_vcpu(p) )

+    /* VCPU's context should not be saved if its domain is
suspended */
+    if ( p->domain->is_shut_down &&
+        (p->domain->shutdown_code == SHUTDOWN_suspend) )
+        return;
SHUTDOWN_suspend is used in Xen for other purpose (see
SCHEDOP_shutdown). The other user of that code relies on all the state
to be saved on suspend.

We just need a flag to mark a domain as suspended, and I do believe
SHUTDOWN_suspend is not used anywhere else.
Let's come back on this.
SHUTDOWN_suspend is used for migration.  Grep for it through the Xen
tree and you'll find several pieces of documentation, including the
description of what this shutdown code means.

What you are introducing here is not a shutdown - it is a suspend with
the intent to resume executing later.  As such, it shouldn't use Xen's
shutdown infrastructure, which exists mainly to communicate with the
Would domain pause/unpause be a better solution?
Actually yes - that sounds like a very neat solution.

I believe domain pause will not work here - a domain cannot pause itself, i.e. current domain cannot be paused. This functionality seems to assume that a domain is pausing another domain. Or I missed the point.


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