[for,4.19,v4,02/10] x86/vlapic: Move lapic migration checks to the check hooks

Commit Message

Alejandro Vallejo June 26, 2024, 4:28 p.m. UTC

While doing this, factor out checks common to architectural and hidden state.

Signed-off-by: Alejandro Vallejo <[e-mail]>
Reviewed-by: Roger Pau Monné <[e-mail]>
---
This puts essential LAPIC information in the stream. It's technically a feature
but it makes 4.19 guests a lot more future-proof. I think this should go on 4.19

v4:
  * Replaced BUG() with ASSERT_UNREACHABLE(), and allow ret -EINVAL on release.
  * Adjust printk() to be clearer
  * Assign lapic_check_common() outside the "if" condition.
---
 xen/arch/x86/hvm/vlapic.c | 85 ++++++++++++++++++++++++++-------------
 1 file changed, 58 insertions(+), 27 deletions(-)

Patch

diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index 9cfc82666ae5..1a7bca5afd2f 100644
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -1553,60 +1553,91 @@  static void lapic_load_fixup(struct vlapic *vlapic)
                v, vlapic->loaded.id, vlapic->loaded.ldr, good_ldr);
 }
 
-static int cf_check lapic_load_hidden(struct domain *d, hvm_domain_context_t *h)
-{
-    unsigned int vcpuid = hvm_load_instance(h);
-    struct vcpu *v;
-    struct vlapic *s;
 
+static int lapic_check_common(const struct domain *d, unsigned int vcpuid)
+{
     if ( !has_vlapic(d) )
         return -ENODEV;
 
     /* Which vlapic to load? */
-    if ( vcpuid >= d->max_vcpus || (v = d->vcpu[vcpuid]) == NULL )
+    if ( !domain_vcpu(d, vcpuid) )
     {
-        dprintk(XENLOG_G_ERR, "HVM restore: dom%d has no apic%u\n",
+        dprintk(XENLOG_G_ERR, "HVM restore: dom%d has no vCPU %u\n",
                 d->domain_id, vcpuid);
         return -EINVAL;
     }
-    s = vcpu_vlapic(v);
+
+    return 0;
+}
+
+static int cf_check lapic_check_hidden(const struct domain *d,
+                                       hvm_domain_context_t *h)
+{
+    unsigned int vcpuid = hvm_load_instance(h);
+    struct hvm_hw_lapic s;
+    int rc = lapic_check_common(d, vcpuid);
+
+    if ( rc )
+        return rc;
+
+    if ( hvm_load_entry_zeroextend(LAPIC, h, &s) != 0 )
+        return -ENODATA;
+
+    /* EN=0 with EXTD=1 is illegal */
+    if ( (s.apic_base_msr & (APIC_BASE_ENABLE | APIC_BASE_EXTD)) ==
+         APIC_BASE_EXTD )
+        return -EINVAL;
+
+    return 0;
+}
+
+static int cf_check lapic_load_hidden(struct domain *d, hvm_domain_context_t *h)
+{
+    unsigned int vcpuid = hvm_load_instance(h);
+    struct vcpu *v = d->vcpu[vcpuid];
+    struct vlapic *s = vcpu_vlapic(v);
 
     if ( hvm_load_entry_zeroextend(LAPIC, h, &s->hw) != 0 )
+    {
+        ASSERT_UNREACHABLE();
         return -EINVAL;
+    }
 
     s->loaded.hw = 1;
     if ( s->loaded.regs )
         lapic_load_fixup(s);
 
-    if ( !(s->hw.apic_base_msr & APIC_BASE_ENABLE) &&
-         unlikely(vlapic_x2apic_mode(s)) )
-        return -EINVAL;
-
     hvm_update_vlapic_mode(v);
 
     return 0;
 }
 
-static int cf_check lapic_load_regs(struct domain *d, hvm_domain_context_t *h)
+static int cf_check lapic_check_regs(const struct domain *d,
+                                     hvm_domain_context_t *h)
 {
     unsigned int vcpuid = hvm_load_instance(h);
-    struct vcpu *v;
-    struct vlapic *s;
+    int rc;
 
-    if ( !has_vlapic(d) )
-        return -ENODEV;
+    if ( (rc = lapic_check_common(d, vcpuid)) )
+        return rc;
 
-    /* Which vlapic to load? */
-    if ( vcpuid >= d->max_vcpus || (v = d->vcpu[vcpuid]) == NULL )
-    {
-        dprintk(XENLOG_G_ERR, "HVM restore: dom%d has no apic%u\n",
-                d->domain_id, vcpuid);
-        return -EINVAL;
-    }
-    s = vcpu_vlapic(v);
+    if ( !hvm_get_entry(LAPIC_REGS, h) )
+        return -ENODATA;
+
+    return 0;
+}
+
+static int cf_check lapic_load_regs(struct domain *d, hvm_domain_context_t *h)
+{
+    unsigned int vcpuid = hvm_load_instance(h);
+    struct vcpu *v = d->vcpu[vcpuid];
+    struct vlapic *s = vcpu_vlapic(v);
 
     if ( hvm_load_entry(LAPIC_REGS, h, s->regs) != 0 )
+    {
+        ASSERT_UNREACHABLE();
         return -EINVAL;
+    }
 
     s->loaded.id = vlapic_get_reg(s, APIC_ID);
     s->loaded.ldr = vlapic_get_reg(s, APIC_LDR);
@@ -1623,9 +1654,9 @@  static int cf_check lapic_load_regs(struct domain *d, hvm_domain_context_t *h)
     return 0;
 }
 
-HVM_REGISTER_SAVE_RESTORE(LAPIC, lapic_save_hidden, NULL,
+HVM_REGISTER_SAVE_RESTORE(LAPIC, lapic_save_hidden, lapic_check_hidden,
                           lapic_load_hidden, 1, HVMSR_PER_VCPU);
-HVM_REGISTER_SAVE_RESTORE(LAPIC_REGS, lapic_save_regs, NULL,
+HVM_REGISTER_SAVE_RESTORE(LAPIC_REGS, lapic_save_regs, lapic_check_regs,
                           lapic_load_regs, 1, HVMSR_PER_VCPU);
 
 int vlapic_init(struct vcpu *v)