Mailing List Archive

From: Paul Durrant <pdurrant@amazon.com>

vlapic_ipi() uses a softirq batching mechanism to improve the efficiency of
sending a IPIs to large number of processors. This patch modifies send_ipi()
(the worker function called by hvcall_ipi()) to also make use of the
mechanism when there multiple bits set the hypercall_vpmask.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
Cc: Wei Liu <wl@xen.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>

v2:
- Don't add the 'nr' field to struct hypercall_vpmask and use
bitmap_weight() instead
---
xen/arch/x86/hvm/viridian/viridian.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/xen/arch/x86/hvm/viridian/viridian.c b/xen/arch/x86/hvm/viridian/viridian.c
index cdfeaec8b96b..4867a1bd140b 100644
--- a/xen/arch/x86/hvm/viridian/viridian.c
+++ b/xen/arch/x86/hvm/viridian/viridian.c
@@ -11,6 +11,7 @@
#include <xen/hypercall.h>
#include <xen/domain_page.h>
#include <xen/param.h>
+#include <xen/softirq.h>
#include <asm/guest/hyperv-tlfs.h>
#include <asm/paging.h>
#include <asm/p2m.h>
@@ -571,6 +572,11 @@ static unsigned int vpmask_next(const struct hypercall_vpmask *vpmask,
(vp) < HVM_MAX_VCPUS; \
(vp) = vpmask_next(vpmask, vp) )

+static unsigned int vpmask_nr(const struct hypercall_vpmask *vpmask)
+{
+ return bitmap_weight(vpmask->mask, HVM_MAX_VCPUS);
+}
+
/*
* Windows should not issue the hypercalls requiring this callback in the
* case where vcpu_id would exceed the size of the mask.
@@ -654,10 +660,17 @@ static int hvcall_flush(const union hypercall_input *input,
static void send_ipi(struct hypercall_vpmask *vpmask, uint8_t vector)
{
struct domain *currd = current->domain;
+ unsigned int nr = vpmask_nr(vpmask);
unsigned int vp;

+ if ( nr > 1 )
+ cpu_raise_softirq_batch_begin();
+
for_each_vp ( vpmask, vp )
vlapic_set_irq(vcpu_vlapic(currd->vcpu[vp]), vector, 0);
+
+ if ( nr > 1 )
+ cpu_raise_softirq_batch_finish();
}

static int hvcall_ipi(const union hypercall_input *input,
--
2.20.1