[Xen-devel] [PATCH for 4.5 v2] vmx, apicv: fix save/restore issue with apicv

[Yang Zhang <yang.z.zhang@xxxxxxxxx>]

From: Yang Zhang <yang.z.zhang@xxxxxxxxx>

This patch fixes two issues:

1. Interrupts on PIR are lost during save/restore. Syncing the PIR
into IRR during save will fix it.

2. EOI exit bitmap doesn't set up correctly after restore. Here we
will construct the eoi exit bitmap via (IRR | ISR). Though it may cause
unnecessary eoi exit of the interrupts that pending in IRR or ISR during
save/restore, each pending interrupt only causes one vmexit. The
subsequent interrupts will adjust the eoi exit bitmap correctly. So
the performance hurt can be ignored.

Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
---
Hi Olaf and Malcolm, please help to retest this version.

 xen/arch/x86/hvm/vlapic.c        |    3 +++
 xen/arch/x86/hvm/vmx/vmx.c       |   24 ++++++++++++++++++++++++
 xen/include/asm-x86/hvm/vlapic.h |    2 ++
 3 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index 089d13f..6691e50 100644
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -1293,6 +1293,9 @@ static int lapic_save_regs(struct domain *d, 
hvm_domain_context_t *h)
 
     for_each_vcpu ( d, v )
     {
+        if ( hvm_funcs.sync_pir_to_irr )
+            hvm_funcs.sync_pir_to_irr(v);
+
         s = vcpu_vlapic(v);
         if ( (rc = hvm_save_entry(LAPIC_REGS, v->vcpu_id, h, s->regs)) != 0 )
             break;
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 304aeea..df4737d 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -1584,6 +1584,8 @@ static void vmx_process_isr(int isr, struct vcpu *v)
 {
     unsigned long status;
     u8 old;
+    unsigned int i, vector;
+    struct vlapic *vlapic = vcpu_vlapic(v);
 
     if ( isr < 0 )
         isr = 0;
@@ -1597,6 +1599,28 @@ static void vmx_process_isr(int isr, struct vcpu *v)
         status |= isr << VMX_GUEST_INTR_STATUS_SVI_OFFSET;
         __vmwrite(GUEST_INTR_STATUS, status);
     }
+
+    /*
+     * Theoretically, only level triggered interrupts can have their
+     * corresponding bits set in the eoi exit bitmap. That is, the bits
+     * set in the eoi exit bitmap should also be set in TMR. But a periodic
+     * timer interrupt does not follow the rule: it is edge triggered, but
+     * requires its corresponding bit be set in the eoi exit bitmap. So we
+     * should not construct the eoi exit bitmap based on TMR.
+     * Here we will construct the eoi exit bitmap via (IRR | ISR). This
+     * means that EOIs to the interrupts that are set in the IRR or ISR will
+     * cause VM exits after restoring, regardless of the trigger modes. It
+     * is acceptable because the subsequent interrupts will set up the eoi
+     * bitmap correctly.
+     */
+    for ( vector = 0x10; vector < NR_VECTORS; vector++ )
+        if ( vlapic_test_vector(vector, &vlapic->regs->data[APIC_IRR]) ||
+             vlapic_test_vector(vector, &vlapic->regs->data[APIC_ISR]) )
+            set_bit(vector,  v->arch.hvm_vmx.eoi_exit_bitmap);
+
+    for ( i = 0; i < 4; i++ )
+        __vmwrite(EOI_EXIT_BITMAP(i), v->arch.hvm_vmx.eoi_exit_bitmap[i]);
+
     vmx_vmcs_exit(v);
 }
 
diff --git a/xen/include/asm-x86/hvm/vlapic.h b/xen/include/asm-x86/hvm/vlapic.h
index 16752b5..384b59a 100644
--- a/xen/include/asm-x86/hvm/vlapic.h
+++ b/xen/include/asm-x86/hvm/vlapic.h
@@ -61,6 +61,8 @@
 
 #define VEC_POS(v) ((v) % 32)
 #define REG_POS(v) (((v) / 32) * 0x10)
+#define vlapic_test_vector(vec, bitmap)                                 \
+    test_bit(VEC_POS(vec), (uint32_t *)((bitmap) + REG_POS(vec)))
 #define vlapic_test_and_set_vector(vec, bitmap)                         \
     test_and_set_bit(VEC_POS(vec), (uint32_t *)((bitmap) + REG_POS(vec)))
 #define vlapic_test_and_clear_vector(vec, bitmap)                       \
-- 
1.7.6.3


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