[PATCH] x86/hvm: process softirq while saving/loading entries

[PATCH] x86/hvm: process softirq while saving/loading entries

[Roger Pau Monne]

On slow systems with sync_console saving or loading the context of big
guests can cause the watchdog to trigger. Fix this by adding a couple
of process_pending_softirqs.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
 xen/arch/x86/hvm/save.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/xen/arch/x86/hvm/save.c b/xen/arch/x86/hvm/save.c
index a2c56fbc1e..584620985b 100644
--- a/xen/arch/x86/hvm/save.c
+++ b/xen/arch/x86/hvm/save.c
@@ -21,6 +21,7 @@
  */
 
 #include <xen/guest_access.h>
+#include <xen/softirq.h>
 #include <xen/version.h>
 
 #include <asm/hvm/support.h>
@@ -255,6 +256,7 @@ int hvm_save(struct domain *d, hvm_domain_context_t *h)
                            v, i);
                     return -ENODATA;
                 }
+                process_pending_softirqs();
             }
         }
         else
@@ -268,6 +270,7 @@ int hvm_save(struct domain *d, hvm_domain_context_t *h)
                        d->domain_id, i);
                 return -ENODATA;
             }
+            process_pending_softirqs();
         }
     }
 
@@ -341,6 +344,7 @@ int hvm_load(struct domain *d, hvm_domain_context_t *h)
                    d->domain_id, desc->typecode, desc->instance);
             return -1;
         }
+        process_pending_softirqs();
     }
 
     /* Not reached */
-- 
2.29.0

Re: [PATCH] x86/hvm: process softirq while saving/loading entries

[Jan Beulich]

On 29.10.2020 16:20, Roger Pau Monne wrote:
> On slow systems with sync_console saving or loading the context of big
> guests can cause the watchdog to trigger. Fix this by adding a couple
> of process_pending_softirqs.

Which raises the question in how far this is then also a problem
for the caller of the underlying hypercall. IOW I wonder whether
instead we need to make use of continuations here. Nevertheless
...

> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Acked-by: Jan Beulich <jbeulich@suse.com>

Jan

Re: [PATCH] x86/hvm: process softirq while saving/loading entries

[Roger Pau Monné]

On Thu, Oct 29, 2020 at 05:38:17PM +0100, Jan Beulich wrote:
> On 29.10.2020 16:20, Roger Pau Monne wrote:
> > On slow systems with sync_console saving or loading the context of big
> > guests can cause the watchdog to trigger. Fix this by adding a couple
> > of process_pending_softirqs.
> 
> Which raises the question in how far this is then also a problem
> for the caller of the underlying hypercall. IOW I wonder whether
> instead we need to make use of continuations here. Nevertheless

FWIW, I've only hit this with debug builds on boxes that have slow
serial with sync_console enabled, due to the verbose printks.

> 
> > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> 
> Acked-by: Jan Beulich <jbeulich@suse.com>

Thanks.