[Xen-devel] [PATCH 1/2] xen, libxc: Introduced XEN_DOMCTL_emulate_each_rep

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

Previously, if vm_event emulation support was enabled, then REP
optimizations were disabled when emulating REP-compatible
instructions. This patch allows fine-tuning of this behaviour by
providing a dedicated libxc helper function.

Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
---
 tools/libxc/include/xenctrl.h    |   11 +++++++++++
 tools/libxc/xc_domain.c          |   18 ++++++++++++++++++
 xen/arch/x86/hvm/emulate.c       |    2 +-
 xen/common/domctl.c              |    5 +++++
 xen/include/asm-x86/hvm/domain.h |    1 +
 xen/include/public/domctl.h      |    8 ++++++++
 6 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index 3482544..4ece851 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -643,6 +643,17 @@ int xc_domain_node_getaffinity(xc_interface *xch,
                                xc_nodemap_t nodemap);
 
 /**
+ * This function enables / disables emulation for each REP for a
+ * REP-compatible instruction.
+ *
+ * @parm xch a handle to an open hypervisor interface.
+ * @parm domid the domain id one wants to get the node affinity of.
+ * @parm enable if 0 optimize when possible, else emulate each REP.
+ * @return 0 on success, -1 on failure.
+ */
+int xc_domain_emulate_each_rep(xc_interface *xch, uint32_t domid, int enable);
+
+/**
  * This function specifies the CPU affinity for a vcpu.
  *
  * There are two kinds of affinity. Soft affinity is on what CPUs a vcpu
diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c
index e7278dd..19b2e46 100644
--- a/tools/libxc/xc_domain.c
+++ b/tools/libxc/xc_domain.c
@@ -2555,6 +2555,24 @@ int xc_domain_soft_reset(xc_interface *xch,
     domctl.domain = (domid_t)domid;
     return do_domctl(xch, &domctl);
 }
+
+int xc_domain_emulate_each_rep(xc_interface *xch, uint32_t domid, int enable)
+{
+    int ret = -1;
+    DECLARE_DOMCTL;
+
+    domctl.cmd = XEN_DOMCTL_emulate_each_rep;
+    domctl.domain = (domid_t)domid;
+    domctl.u.emulate_each_rep.op = enable;
+
+    ret = do_domctl(xch, &domctl);
+
+    if ( ret == -ESRCH )
+        errno = ENOENT;
+
+    return ret;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index 5934c72..649eb7f 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -514,7 +514,7 @@ static int hvmemul_virtual_to_linear(
      * being triggered for repeated writes to a whole page.
      */
     *reps = min_t(unsigned long, *reps,
-                  unlikely(current->domain->arch.mem_access_emulate_enabled)
+                  unlikely(current->domain->arch.hvm_domain.emulate_each_rep)
                            ? 1 : 4096);
 
     reg = hvmemul_get_seg_reg(seg, hvmemul_ctxt);
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 9e0fef5..214a22a 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -1180,6 +1180,11 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
             copyback = 1;
         break;
 
+    case XEN_DOMCTL_emulate_each_rep:
+        d->arch.hvm_domain.emulate_each_rep = !!op->u.emulate_each_rep.op;
+        ret = 0;
+        break;
+
     default:
         ret = arch_do_domctl(op, d, u_domctl);
         break;
diff --git a/xen/include/asm-x86/hvm/domain.h b/xen/include/asm-x86/hvm/domain.h
index 992d5d1..b8fbe5e 100644
--- a/xen/include/asm-x86/hvm/domain.h
+++ b/xen/include/asm-x86/hvm/domain.h
@@ -136,6 +136,7 @@ struct hvm_domain {
     bool_t                 mem_sharing_enabled;
     bool_t                 qemu_mapcache_invalidate;
     bool_t                 is_s3_suspended;
+    bool_t                 emulate_each_rep;
 
     /*
      * TSC value that VCPUs use to calculate their tsc_offset value.
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 794d4d5..efc42a8 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -1063,6 +1063,12 @@ struct xen_domctl_psr_cat_op {
 typedef struct xen_domctl_psr_cat_op xen_domctl_psr_cat_op_t;
 DEFINE_XEN_GUEST_HANDLE(xen_domctl_psr_cat_op_t);
 
+struct xen_domctl_emulate_each_rep {
+    int32_t op;
+};
+typedef struct xen_domctl_emulate_each_rep xen_domctl_emulate_each_rep_t;
+DEFINE_XEN_GUEST_HANDLE(xen_domctl_emulate_each_rep_t);
+
 struct xen_domctl {
     uint32_t cmd;
 #define XEN_DOMCTL_createdomain                   1
@@ -1140,6 +1146,7 @@ struct xen_domctl {
 #define XEN_DOMCTL_monitor_op                    77
 #define XEN_DOMCTL_psr_cat_op                    78
 #define XEN_DOMCTL_soft_reset                    79
+#define XEN_DOMCTL_emulate_each_rep              80
 #define XEN_DOMCTL_gdbsx_guestmemio            1000
 #define XEN_DOMCTL_gdbsx_pausevcpu             1001
 #define XEN_DOMCTL_gdbsx_unpausevcpu           1002
@@ -1202,6 +1209,7 @@ struct xen_domctl {
         struct xen_domctl_psr_cmt_op        psr_cmt_op;
         struct xen_domctl_monitor_op        monitor_op;
         struct xen_domctl_psr_cat_op        psr_cat_op;
+        struct xen_domctl_emulate_each_rep  emulate_each_rep;
         uint8_t                             pad[128];
     } u;
 };
-- 
1.7.9.5


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