[Xen-devel] [PATCH RFC] VMX: fix vmx_handle_eoi()

["Jan Beulich" <JBeulich@xxxxxxxx>]

In commit 303066fdb1e ("VMX: fix interaction of APIC-V and Viridian
emulation") I screwed up quite heavily: Instead of clearing SVI, RVI was
cleared. Furthermore, unconditional clearing of SVI is wrong too - other
ISR bits should be taken into account.

Introduce a new helper set_svi(), split out of vmx_process_isr(), and
use it also from vmx_handle_eoi().

Following the problems in vmx_intr_assist() (see the still present big
block of debugging code there) also warn (once) if EOI'd vector and
original SVI don't match.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
RFC: Untested, as I didn't see any of the possibly resulting problems
     in any of my environments. But perhaps this is (part of) the
     reason of lost interrupts XenServer folks have been observing.

--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -448,7 +448,7 @@ void vlapic_EOI_set(struct vlapic *vlapi
     vlapic_clear_vector(vector, &vlapic->regs->data[APIC_ISR]);
 
     if ( hvm_funcs.handle_eoi )
-        hvm_funcs.handle_eoi(vector);
+        hvm_funcs.handle_eoi(vector, vlapic_find_highest_isr(vlapic));
 
     vlapic_handle_EOI(vlapic, vector);
 
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -1941,17 +1941,14 @@ static void vmx_update_eoi_exit_bitmap(s
         vmx_clear_eoi_exit_bitmap(v, vector);
 }
 
-static void vmx_process_isr(int isr, struct vcpu *v)
+static u8 set_svi(int isr)
 {
     unsigned long status;
     u8 old;
-    unsigned int i;
-    const struct vlapic *vlapic = vcpu_vlapic(v);
 
     if ( isr < 0 )
         isr = 0;
 
-    vmx_vmcs_enter(v);
     __vmread(GUEST_INTR_STATUS, &status);
     old = status >> VMX_GUEST_INTR_STATUS_SVI_OFFSET;
     if ( isr != old )
@@ -1961,6 +1958,18 @@ static void vmx_process_isr(int isr, str
         __vmwrite(GUEST_INTR_STATUS, status);
     }
 
+    return old;
+}
+
+static void vmx_process_isr(int isr, struct vcpu *v)
+{
+    unsigned int i;
+    const struct vlapic *vlapic = vcpu_vlapic(v);
+
+    vmx_vmcs_enter(v);
+
+    set_svi(isr);
+
     /*
      * Theoretically, only level triggered interrupts can have their
      * corresponding bits set in the eoi exit bitmap. That is, the bits
@@ -2111,14 +2120,13 @@ static bool vmx_test_pir(const struct vc
     return pi_test_pir(vec, &v->arch.hvm.vmx.pi_desc);
 }
 
-static void vmx_handle_eoi(u8 vector)
+static void vmx_handle_eoi(uint8_t vector, int isr)
 {
-    unsigned long status;
+    u8 old_svi = set_svi(isr);
+    static bool warned;
 
-    /* We need to clear the SVI field. */
-    __vmread(GUEST_INTR_STATUS, &status);
-    status &= VMX_GUEST_INTR_STATUS_SUBFIELD_BITMASK;
-    __vmwrite(GUEST_INTR_STATUS, status);
+    if ( vector != old_svi && !test_and_set_bool(warned) )
+        printk(XENLOG_WARNING "EOI for %02x but SVI=%02x\n", vector, old_svi);
 }
 
 static void vmx_enable_msr_interception(struct domain *d, uint32_t msr)
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -201,7 +201,7 @@ struct hvm_function_table {
     void (*deliver_posted_intr)(struct vcpu *v, u8 vector);
     void (*sync_pir_to_irr)(struct vcpu *v);
     bool (*test_pir)(const struct vcpu *v, uint8_t vector);
-    void (*handle_eoi)(u8 vector);
+    void (*handle_eoi)(uint8_t vector, int isr);
 
     /*Walk nested p2m  */
     int (*nhvm_hap_walk_L1_p2m)(struct vcpu *v, paddr_t L2_gpa,





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