[Xen-devel] [PATCH v7 01/10] x86/hypervisor: make hypervisor_ap_setup return an error code

[Wei Liu <wl@xxxxxxx>]

We want to be able to handle AP setup error in the upper layer.

For Xen, remove all panic() and BUG_ON() in init_evtchn and
map_vcpuinfo. Only panic/BUG_ON when Xen can't fail gracefully.

Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>
---
v7:
1. Change init_evtchn

v6:
1. Change map_vcpuinfo as well
2. Make code shorter
---
 xen/arch/x86/guest/hypervisor.c        |  6 ++-
 xen/arch/x86/guest/xen/xen.c           | 58 ++++++++++++++++----------
 xen/include/asm-x86/guest/hypervisor.h |  6 +--
 3 files changed, 42 insertions(+), 28 deletions(-)

diff --git a/xen/arch/x86/guest/hypervisor.c b/xen/arch/x86/guest/hypervisor.c
index 4f27b98740..e72c92ffdf 100644
--- a/xen/arch/x86/guest/hypervisor.c
+++ b/xen/arch/x86/guest/hypervisor.c
@@ -52,10 +52,12 @@ void __init hypervisor_setup(void)
         ops->setup();
 }
 
-void hypervisor_ap_setup(void)
+int hypervisor_ap_setup(void)
 {
     if ( ops && ops->ap_setup )
-        ops->ap_setup();
+        return ops->ap_setup();
+
+    return 0;
 }
 
 void hypervisor_resume(void)
diff --git a/xen/arch/x86/guest/xen/xen.c b/xen/arch/x86/guest/xen/xen.c
index 6dbc5f953f..1cf09886da 100644
--- a/xen/arch/x86/guest/xen/xen.c
+++ b/xen/arch/x86/guest/xen/xen.c
@@ -113,16 +113,16 @@ static int map_vcpuinfo(void)
     info.mfn = virt_to_mfn(&vcpu_info[vcpu]);
     info.offset = (unsigned long)&vcpu_info[vcpu] & ~PAGE_MASK;
     rc = xen_hypercall_vcpu_op(VCPUOP_register_vcpu_info, vcpu, &info);
-    if ( rc )
-    {
-        BUG_ON(vcpu >= XEN_LEGACY_MAX_VCPUS);
-        this_cpu(vcpu_info) = &XEN_shared_info->vcpu_info[vcpu];
-    }
-    else
+    if ( !rc )
     {
         this_cpu(vcpu_info) = &vcpu_info[vcpu];
         set_bit(vcpu, vcpu_info_mapped);
     }
+    else if ( vcpu < XEN_LEGACY_MAX_VCPUS )
+    {
+        rc = 0;
+        this_cpu(vcpu_info) = &XEN_shared_info->vcpu_info[vcpu];
+    }
 
     return rc;
 }
@@ -202,10 +202,15 @@ static void xen_evtchn_upcall(struct cpu_user_regs *regs)
     ack_APIC_irq();
 }
 
-static void init_evtchn(void)
+static int init_evtchn(void)
 {
     static uint8_t evtchn_upcall_vector;
     int rc;
+    struct xen_hvm_param a = {
+        .domid = DOMID_SELF,
+        .index = HVM_PARAM_CALLBACK_IRQ,
+        .value = 1,
+    };
 
     if ( !evtchn_upcall_vector )
         alloc_direct_apic_vector(&evtchn_upcall_vector, xen_evtchn_upcall);
@@ -215,18 +220,19 @@ static void init_evtchn(void)
     rc = xen_hypercall_set_evtchn_upcall_vector(this_cpu(vcpu_id),
                                                 evtchn_upcall_vector);
     if ( rc )
-        panic("Unable to set evtchn upcall vector: %d\n", rc);
+    {
+        printk("Unable to set evtchn upcall vector: %d\n", rc);
+        goto out;
+    }
 
     /* Trick toolstack to think we are enlightened */
-    {
-        struct xen_hvm_param a = {
-            .domid = DOMID_SELF,
-            .index = HVM_PARAM_CALLBACK_IRQ,
-            .value = 1,
-        };
+    rc = xen_hypercall_hvm_op(HVMOP_set_param, &a);
 
-        BUG_ON(xen_hypercall_hvm_op(HVMOP_set_param, &a));
-    }
+    if ( rc )
+        printk("Unable to set HVM_PARAM_CALLBACK_IRQ\n");
+
+ out:
+    return rc;
 }
 
 static void __init setup(void)
@@ -254,14 +260,20 @@ static void __init setup(void)
                XEN_LEGACY_MAX_VCPUS);
     }
 
-    init_evtchn();
+    BUG_ON(init_evtchn());
 }
 
-static void ap_setup(void)
+static int ap_setup(void)
 {
+    int rc;
+
     set_vcpu_id();
-    map_vcpuinfo();
-    init_evtchn();
+
+    rc = map_vcpuinfo();
+    if ( rc )
+        return rc;
+
+    return init_evtchn();
 }
 
 int xg_alloc_unused_page(mfn_t *mfn)
@@ -283,8 +295,8 @@ int xg_free_unused_page(mfn_t mfn)
 
 static void ap_resume(void *unused)
 {
-    map_vcpuinfo();
-    init_evtchn();
+    BUG_ON(map_vcpuinfo());
+    BUG_ON(init_evtchn());
 }
 
 static void resume(void)
@@ -303,7 +315,7 @@ static void resume(void)
         panic("unable to remap vCPU info and vCPUs > legacy limit\n");
 
     /* Setup event channel upcall vector. */
-    init_evtchn();
+    BUG_ON(init_evtchn());
     smp_call_function(ap_resume, NULL, 1);
 
     if ( pv_console )
diff --git a/xen/include/asm-x86/guest/hypervisor.h 
b/xen/include/asm-x86/guest/hypervisor.h
index 392f4b90ae..b503854c5b 100644
--- a/xen/include/asm-x86/guest/hypervisor.h
+++ b/xen/include/asm-x86/guest/hypervisor.h
@@ -25,7 +25,7 @@ struct hypervisor_ops {
     /* Main setup routine */
     void (*setup)(void);
     /* AP setup */
-    void (*ap_setup)(void);
+    int (*ap_setup)(void);
     /* Resume from suspension */
     void (*resume)(void);
 };
@@ -34,7 +34,7 @@ struct hypervisor_ops {
 
 const char *hypervisor_probe(void);
 void hypervisor_setup(void);
-void hypervisor_ap_setup(void);
+int hypervisor_ap_setup(void);
 void hypervisor_resume(void);
 
 #else
@@ -44,7 +44,7 @@ void hypervisor_resume(void);
 
 static inline const char *hypervisor_probe(void) { return NULL; }
 static inline void hypervisor_setup(void) { ASSERT_UNREACHABLE(); }
-static inline void hypervisor_ap_setup(void) { ASSERT_UNREACHABLE(); }
+static inline int hypervisor_ap_setup(void) { ASSERT_UNREACHABLE(); return 0; }
 static inline void hypervisor_resume(void) { ASSERT_UNREACHABLE(); }
 
 #endif  /* CONFIG_GUEST */
-- 
2.20.1


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