Re: [PATCH] x86/xen: Add support for HVMOP_set_evtchn_upcall_vector

[Boris Ostrovsky]

On 7/11/22 11:22 AM, Jane Malalane wrote:

--- a/arch/x86/xen/enlighten_hvm.c
+++ b/arch/x86/xen/enlighten_hvm.c
@@ -7,6 +7,7 @@

#include <xen/features.h>

  #include <xen/events.h>
+#include <xen/interface/hvm/hvm_op.h>
  #include <xen/interface/memory.h>

#include <asm/apic.h>

@@ -30,6 +31,9 @@

static unsigned long shared_info_pfn; +__ro_after_init bool xen_ack_upcall;

+EXPORT_SYMBOL_GPL(xen_ack_upcall);

Shouldn't this be called something like xen_percpu_upcall?

+
  void xen_hvm_init_shared_info(void)
  {
        struct xen_add_to_physmap xatp;
@@ -125,6 +129,9 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_xen_hvm_callback)
  {
        struct pt_regs *old_regs = set_irq_regs(regs);

+ if (xen_ack_upcall)

+               ack_APIC_irq();
+
        inc_irq_stat(irq_hv_callback_count);

xen_hvm_evtchn_do_upcall();

@@ -168,6 +175,15 @@ static int xen_cpu_up_prepare_hvm(unsigned int cpu)
        if (!xen_have_vector_callback)
                return 0;

+ if (xen_ack_upcall) {

+               xen_hvm_evtchn_upcall_vector_t op = {
+                       .vector = HYPERVISOR_CALLBACK_VECTOR,
+                       .vcpu = per_cpu(xen_vcpu_id, cpu),
+               };
+
+               BUG_ON(HYPERVISOR_hvm_op(HVMOP_set_evtchn_upcall_vector, &op));

Does this have to be fatal? Can't we just fail bringing this vcpu up?

+       }
+
        if (xen_feature(XENFEAT_hvm_safe_pvclock))
                xen_setup_timer(cpu);

@@ -211,8 +227,7 @@ static void __init xen_hvm_guest_init(void) xen_panic_handler_init(); - if (!no_vector_callback && xen_feature(XENFEAT_hvm_callback_vector))

-               xen_have_vector_callback = 1;
+       xen_have_vector_callback = !no_vector_callback;

Can we get rid of one of those two variables then?

xen_hvm_smp_init();

        WARN_ON(xen_cpuhp_setup(xen_cpu_up_prepare_hvm, xen_cpu_dead_hvm));
diff --git a/arch/x86/xen/suspend_hvm.c b/arch/x86/xen/suspend_hvm.c
index 9d548b0c772f..be66e027ef28 100644
--- a/arch/x86/xen/suspend_hvm.c
+++ b/arch/x86/xen/suspend_hvm.c
@@ -5,6 +5,7 @@
  #include <xen/hvm.h>
  #include <xen/features.h>
  #include <xen/interface/features.h>
+#include <xen/events.h>

#include "xen-ops.h" @@ -14,6 +15,23 @@ void xen_hvm_post_suspend(int suspend_cancelled)

                xen_hvm_init_shared_info();
                xen_vcpu_restore();
        }
-       xen_setup_callback_vector();
+       if (xen_ack_upcall) {
+               unsigned int cpu;
+
+               for_each_online_cpu(cpu) {
+                       xen_hvm_evtchn_upcall_vector_t op = {
+                                       .vector = HYPERVISOR_CALLBACK_VECTOR,
+                                       .vcpu = per_cpu(xen_vcpu_id, cpu),
+                       };
+
+                       BUG_ON(HYPERVISOR_hvm_op(HVMOP_set_evtchn_upcall_vector,
+                                                &op));
+                       /* Trick toolstack to think we are enlightened. */
+                       if (!cpu)
+                               BUG_ON(xen_set_callback_via(1));

What are you trying to make the toolstack aware of? That we have *a* callback 
(either global or percpu)?


BTW, you can take it out the loop. And maybe @op definition too, except for 
.vcpu assignment.

+               }
+       } else {
+               xen_setup_callback_vector();
+       }
        xen_unplug_emulated_devices();
  }

-boris