x86/xen: Add support for HVMOP_set_evtchn_upcall_vector

Implement support for the HVMOP_set_evtchn_upcall_vector hypercall in order to set the per-vCPU event channel vector callback on Linux and use it in preference of HVM_PARAM_CALLBACK_IRQ. If the per-VCPU vector setup is successful on BSP, use this method for the APs. If not, fallback to the global vector-type callback. Also register callback_irq at per-vCPU event channel setup to trick toolstack to think the domain is enlightened. Suggested-by: "Roger Pau Monné" <[email protected]> Signed-off-by: Jane Malalane <[email protected]> Reviewed-by: Boris Ostrovsky <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Juergen Gross <[email protected]>
torvalds · Aug 12, 2022 · b1c3497 · b1c3497
1 parent 251e90e
commit b1c3497
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Showing 8 changed files with 100 additions and 15 deletions.
diff --git a/arch/x86/include/asm/xen/cpuid.h b/arch/x86/include/asm/xen/cpuid.h
@@ -107,6 +107,8 @@
  * ID field from 8 to 15 bits, allowing to target APIC IDs up 32768.
  */
 #define XEN_HVM_CPUID_EXT_DEST_ID (1u << 5)
+/* Per-vCPU event channel upcalls */
+#define XEN_HVM_CPUID_UPCALL_VECTOR (1u << 6)
 
 /*
  * Leaf 6 (0x40000x05)

diff --git a/arch/x86/include/asm/xen/events.h b/arch/x86/include/asm/xen/events.h
@@ -23,7 +23,7 @@ static inline int xen_irqs_disabled(struct pt_regs *regs)
 /* No need for a barrier -- XCHG is a barrier on x86. */
 #define xchg_xen_ulong(ptr, val) xchg((ptr), (val))
 
-extern int xen_have_vector_callback;
+extern bool xen_have_vector_callback;
 
 /*
  * Events delivered via platform PCI interrupts are always
@@ -34,4 +34,5 @@ static inline bool xen_support_evtchn_rebind(void)
  return (!xen_hvm_domain() || xen_have_vector_callback);
 }
 
+extern bool xen_percpu_upcall;
 #endif /* _ASM_X86_XEN_EVENTS_H */
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
@@ -51,7 +51,7 @@ EXPORT_SYMBOL_GPL(xen_start_info);
 
 struct shared_info xen_dummy_shared_info;
 
-__read_mostly int xen_have_vector_callback;
+__read_mostly bool xen_have_vector_callback = true;
 EXPORT_SYMBOL_GPL(xen_have_vector_callback);
 
 /*

diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
@@ -8,6 +8,8 @@
 
 #include <xen/features.h>
 #include <xen/events.h>
+#include <xen/hvm.h>
+#include <xen/interface/hvm/hvm_op.h>
 #include <xen/interface/memory.h>
 
 #include <asm/apic.h>
@@ -31,6 +33,9 @@
 
 static unsigned long shared_info_pfn;
 
+__ro_after_init bool xen_percpu_upcall;
+EXPORT_SYMBOL_GPL(xen_percpu_upcall);
+
 void xen_hvm_init_shared_info(void)
 {
  struct xen_add_to_physmap xatp;
@@ -126,6 +131,9 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_xen_hvm_callback)
 {
  struct pt_regs *old_regs = set_irq_regs(regs);
 
+ if (xen_percpu_upcall)
+ ack_APIC_irq();
+
  inc_irq_stat(irq_hv_callback_count);
 
  xen_hvm_evtchn_do_upcall();
@@ -169,6 +177,15 @@ static int xen_cpu_up_prepare_hvm(unsigned int cpu)
  if (!xen_have_vector_callback)
  return 0;
 
+ if (xen_percpu_upcall) {
+ rc = xen_set_upcall_vector(cpu);
+ if (rc) {
+ WARN(1, "HVMOP_set_evtchn_upcall_vector"
+ " for CPU %d failed: %d\n", cpu, rc);
+ return rc;
+ }
+ }
+
  if (xen_feature(XENFEAT_hvm_safe_pvclock))
  xen_setup_timer(cpu);
 
@@ -189,8 +206,6 @@ static int xen_cpu_dead_hvm(unsigned int cpu)
  return 0;
 }
 
-static bool no_vector_callback __initdata;
-
 static void __init xen_hvm_guest_init(void)
 {
  if (xen_pv_domain())
@@ -213,9 +228,6 @@ 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_hvm_smp_init();
  WARN_ON(xen_cpuhp_setup(xen_cpu_up_prepare_hvm, xen_cpu_dead_hvm));
  xen_unplug_emulated_devices();
@@ -241,7 +253,7 @@ early_param("xen_nopv", xen_parse_nopv);
 
 static __init int xen_parse_no_vector_callback(char *arg)
 {
- no_vector_callback = true;
+ xen_have_vector_callback = false;
  return 0;
 }
 early_param("xen_no_vector_callback", xen_parse_no_vector_callback);

diff --git 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 +15,13 @@ void xen_hvm_post_suspend(int suspend_cancelled)
  xen_hvm_init_shared_info();
  xen_vcpu_restore();
  }
- xen_setup_callback_vector();
+ if (xen_percpu_upcall) {
+ unsigned int cpu;
+
+ for_each_online_cpu(cpu)
+ BUG_ON(xen_set_upcall_vector(cpu));
+ } else {
+ xen_setup_callback_vector();
+ }
  xen_unplug_emulated_devices();
 }
diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
@@ -45,6 +45,7 @@
 #include <asm/irq.h>
 #include <asm/io_apic.h>
 #include <asm/i8259.h>
+#include <asm/xen/cpuid.h>
 #include <asm/xen/pci.h>
 #endif
 #include <asm/sync_bitops.h>
@@ -2183,6 +2184,7 @@ static struct irq_chip xen_percpu_chip __read_mostly = {
  .irq_ack = ack_dynirq,
 };
 
+#ifdef CONFIG_X86
 #ifdef CONFIG_XEN_PVHVM
 /* Vector callbacks are better than PCI interrupts to receive event
  * channel notifications because we can receive vector callbacks on any
@@ -2195,11 +2197,48 @@ void xen_setup_callback_vector(void)
  callback_via = HVM_CALLBACK_VECTOR(HYPERVISOR_CALLBACK_VECTOR);
  if (xen_set_callback_via(callback_via)) {
  pr_err("Request for Xen HVM callback vector failed\n");
- xen_have_vector_callback = 0;
+ xen_have_vector_callback = false;
  }
  }
 }
 
+/*
+ * Setup per-vCPU vector-type callbacks. If this setup is unavailable,
+ * fallback to the global vector-type callback.
+ */
+static __init void xen_init_setup_upcall_vector(void)
+{
+ if (!xen_have_vector_callback)
+ return;
+
+ if ((cpuid_eax(xen_cpuid_base() + 4) & XEN_HVM_CPUID_UPCALL_VECTOR) &&
+ !xen_set_upcall_vector(0))
+ xen_percpu_upcall = true;
+ else if (xen_feature(XENFEAT_hvm_callback_vector))
+ xen_setup_callback_vector();
+ else
+ xen_have_vector_callback = false;
+}
+
+int xen_set_upcall_vector(unsigned int cpu)
+{
+ int rc;
+ xen_hvm_evtchn_upcall_vector_t op = {
+ .vector = HYPERVISOR_CALLBACK_VECTOR,
+ .vcpu = per_cpu(xen_vcpu_id, cpu),
+ };
+
+ rc = HYPERVISOR_hvm_op(HVMOP_set_evtchn_upcall_vector, &op);
+ if (rc)
+ return rc;
+
+ /* Trick toolstack to think we are enlightened. */
+ if (!cpu)
+ rc = xen_set_callback_via(1);
+
+ return rc;
+}
+
 static __init void xen_alloc_callback_vector(void)
 {
  if (!xen_have_vector_callback)
@@ -2210,8 +2249,11 @@ static __init void xen_alloc_callback_vector(void)
 }
 #else
 void xen_setup_callback_vector(void) {}
+static inline void xen_init_setup_upcall_vector(void) {}
+int xen_set_upcall_vector(unsigned int cpu) {}
 static inline void xen_alloc_callback_vector(void) {}
-#endif
+#endif /* CONFIG_XEN_PVHVM */
+#endif /* CONFIG_X86 */
 
 bool xen_fifo_events = true;
 module_param_named(fifo_events, xen_fifo_events, bool, 0);
@@ -2271,10 +2313,9 @@ void __init xen_init_IRQ(void)
  if (xen_initial_domain())
  pci_xen_initial_domain();
  }
- if (xen_feature(XENFEAT_hvm_callback_vector)) {
- xen_setup_callback_vector();
- xen_alloc_callback_vector();
- }
+ xen_init_setup_upcall_vector();
+ xen_alloc_callback_vector();
+
 
  if (xen_hvm_domain()) {
  native_init_IRQ();

diff --git a/include/xen/hvm.h b/include/xen/hvm.h
@@ -60,4 +60,6 @@ static inline int hvm_get_parameter(int idx, uint64_t *value)
 
 void xen_setup_callback_vector(void);
 
+int xen_set_upcall_vector(unsigned int cpu);
+
 #endif /* XEN_HVM_H__ */
diff --git a/include/xen/interface/hvm/hvm_op.h b/include/xen/interface/hvm/hvm_op.h
@@ -46,4 +46,23 @@ struct xen_hvm_get_mem_type {
 };
 DEFINE_GUEST_HANDLE_STRUCT(xen_hvm_get_mem_type);
 
+#if defined(__i386__) || defined(__x86_64__)
+
+/*
+ * HVMOP_set_evtchn_upcall_vector: Set a <vector> that should be used for event
+ * channel upcalls on the specified <vcpu>. If set,
+ * this vector will be used in preference to the
+ * domain global callback via (see
+ * HVM_PARAM_CALLBACK_IRQ).
+ */
+#define HVMOP_set_evtchn_upcall_vector 23
+struct xen_hvm_evtchn_upcall_vector {
+ uint32_t vcpu;
+ uint8_t vector;
+};
+typedef struct xen_hvm_evtchn_upcall_vector xen_hvm_evtchn_upcall_vector_t;
+DEFINE_GUEST_HANDLE_STRUCT(xen_hvm_evtchn_upcall_vector_t);
+
+#endif /* defined(__i386__) || defined(__x86_64__) */
+
 #endif /* __XEN_PUBLIC_HVM_HVM_OP_H__ */