[PATCH v2] x86 / viridian: remove the viridian_vcpu msg_pending bit mask

[Paul Durrant <paul@xxxxxxx>]

From: Paul Durrant <pdurrant@xxxxxxxxxx>

The mask does not actually serve a useful purpose as we only use the SynIC
for timer messages. Dropping the mask means that the EOM MSR handler
essentially becomes a no-op. This means we can avoid setting 'message_pending'
for timer messages and hence avoid a VMEXIT for the EOM.

Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
Reviewed-by: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
---
Cc: Wei Liu <wl@xxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

v2:
 - Clean up now extraneous comment noticed by Roger

This should hopefully simplify Roger's "x86/vlapic: implement EOI callbacks"
series a little.
---
 xen/arch/x86/hvm/viridian/synic.c  | 24 +-----------------------
 xen/arch/x86/hvm/vlapic.c          |  4 ----
 xen/include/asm-x86/hvm/viridian.h |  2 --
 3 files changed, 1 insertion(+), 29 deletions(-)

diff --git a/xen/arch/x86/hvm/viridian/synic.c 
b/xen/arch/x86/hvm/viridian/synic.c
index 94a2b88733..22e2df27e5 100644
--- a/xen/arch/x86/hvm/viridian/synic.c
+++ b/xen/arch/x86/hvm/viridian/synic.c
@@ -137,7 +137,6 @@ int viridian_synic_wrmsr(struct vcpu *v, uint32_t idx, 
uint64_t val)
         if ( !(viridian_feature_mask(d) & HVMPV_synic) )
             return X86EMUL_EXCEPTION;
 
-        vv->msg_pending = 0;
         break;
 
     case HV_X64_MSR_SINT0 ... HV_X64_MSR_SINT15:
@@ -168,9 +167,6 @@ int viridian_synic_wrmsr(struct vcpu *v, uint32_t idx, 
uint64_t val)
         printk(XENLOG_G_INFO "%pv: VIRIDIAN SINT%u: vector: %x\n", v, sintx,
                vector);
 
-        if ( new.polling )
-            __clear_bit(sintx, &vv->msg_pending);
-
         *vs = new;
         break;
     }
@@ -334,9 +330,6 @@ bool viridian_synic_deliver_timer_msg(struct vcpu *v, 
unsigned int sintx,
         .DeliveryTime = delivery,
     };
 
-    if ( test_bit(sintx, &vv->msg_pending) )
-        return false;
-
     /*
      * To avoid using an atomic test-and-set, and barrier before calling
      * vlapic_set_irq(), this function must be called in context of the
@@ -346,12 +339,9 @@ bool viridian_synic_deliver_timer_msg(struct vcpu *v, 
unsigned int sintx,
 
     msg += sintx;
 
+    /* There is no need to set message_pending as we do not require an EOM */
     if ( msg->header.message_type != HVMSG_NONE )
-    {
-        msg->header.message_flags.msg_pending = 1;
-        __set_bit(sintx, &vv->msg_pending);
         return false;
-    }
 
     msg->header.message_type = HVMSG_TIMER_EXPIRED;
     msg->header.message_flags.msg_pending = 0;
@@ -380,18 +370,6 @@ bool viridian_synic_is_auto_eoi_sint(const struct vcpu *v,
     return vs->auto_eoi;
 }
 
-void viridian_synic_ack_sint(const struct vcpu *v, unsigned int vector)
-{
-    struct viridian_vcpu *vv = v->arch.hvm.viridian;
-    unsigned int sintx = vv->vector_to_sintx[vector];
-
-    ASSERT(v == current);
-
-    if ( sintx < ARRAY_SIZE(vv->sint) )
-        __clear_bit(array_index_nospec(sintx, ARRAY_SIZE(vv->sint)),
-                    &vv->msg_pending);
-}
-
 void viridian_synic_save_vcpu_ctxt(const struct vcpu *v,
                                    struct hvm_viridian_vcpu_context *ctxt)
 {
diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index 7b5c633033..4e3861eb7d 100644
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -462,12 +462,8 @@ void vlapic_handle_EOI(struct vlapic *vlapic, u8 vector)
     struct vcpu *v = vlapic_vcpu(vlapic);
     struct domain *d = v->domain;
 
-    /* All synic SINTx vectors are edge triggered */
-
     if ( vlapic_test_vector(vector, &vlapic->regs->data[APIC_TMR]) )
         vioapic_update_EOI(d, vector);
-    else if ( has_viridian_synic(d) )
-        viridian_synic_ack_sint(v, vector);
 
     hvm_dpci_msi_eoi(d, vector);
 }
diff --git a/xen/include/asm-x86/hvm/viridian.h 
b/xen/include/asm-x86/hvm/viridian.h
index 844e56b38f..cbf77d9c76 100644
--- a/xen/include/asm-x86/hvm/viridian.h
+++ b/xen/include/asm-x86/hvm/viridian.h
@@ -31,7 +31,6 @@ struct viridian_vcpu
     struct viridian_page vp_assist;
     bool apic_assist_pending;
     bool polled;
-    unsigned int msg_pending;
     uint64_t scontrol;
     uint64_t siefp;
     struct viridian_page simp;
@@ -89,7 +88,6 @@ void viridian_apic_assist_clear(const struct vcpu *v);
 void viridian_synic_poll(struct vcpu *v);
 bool viridian_synic_is_auto_eoi_sint(const struct vcpu *v,
                                      unsigned int vector);
-void viridian_synic_ack_sint(const struct vcpu *v, unsigned int vector);
 
 #endif /* __ASM_X86_HVM_VIRIDIAN_H__ */
 
-- 
2.20.1