Re: [RFC PATCH v3 12/58] perf: core/x86: Register a new vector for KVM GUEST PMI

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Hello,

Mingwei Zhang <mizhang@xxxxxxxxxx> writes:

From: Xiong Zhang <xiong.y.zhang@xxxxxxxxxxxxxxx>

Create a new vector in the host IDT for kvm guest PMI handling within
mediated passthrough vPMU. In addition, guest PMI handler registration
is added into x86_set_kvm_irq_handler().

This is the preparation work to support mediated passthrough vPMU to
handle kvm guest PMIs without interference from PMI handler of the host
PMU.

Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
Signed-off-by: Xiong Zhang <xiong.y.zhang@xxxxxxxxxxxxxxx>
Tested-by: Yongwei Ma <yongwei.ma@xxxxxxxxx>
Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
---
  arch/x86/include/asm/hardirq.h                |  1 +
  arch/x86/include/asm/idtentry.h               |  1 +
  arch/x86/include/asm/irq_vectors.h            |  5 ++++-
  arch/x86/kernel/idt.c                         |  1 +
  arch/x86/kernel/irq.c                         | 21 +++++++++++++++++++
  .../beauty/arch/x86/include/asm/irq_vectors.h |  5 ++++-
  6 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index c67fa6ad098a..42a396763c8d 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -19,6 +19,7 @@ typedef struct {
  	unsigned int kvm_posted_intr_ipis;
  	unsigned int kvm_posted_intr_wakeup_ipis;
  	unsigned int kvm_posted_intr_nested_ipis;
+	unsigned int kvm_guest_pmis;
  #endif
  	unsigned int x86_platform_ipis;	/* arch dependent */
  	unsigned int apic_perf_irqs;
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index d4f24499b256..7b1e3e542b1d 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -745,6 +745,7 @@ DECLARE_IDTENTRY_SYSVEC(IRQ_WORK_VECTOR, sysvec_irq_work);
  DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_VECTOR,		sysvec_kvm_posted_intr_ipi);
DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_WAKEUP_VECTOR, sysvec_kvm_posted_intr_wakeup_ipi); DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_NESTED_VECTOR, sysvec_kvm_posted_intr_nested_ipi); +DECLARE_IDTENTRY_SYSVEC(KVM_GUEST_PMI_VECTOR, sysvec_kvm_guest_pmi_handler);
  #else
  # define fred_sysvec_kvm_posted_intr_ipi		NULL
  # define fred_sysvec_kvm_posted_intr_wakeup_ipi		NULL
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index 13aea8fc3d45..ada270e6f5cb 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -77,7 +77,10 @@
   */
  #define IRQ_WORK_VECTOR			0xf6

-/* 0xf5 - unused, was UV_BAU_MESSAGE */
+#if IS_ENABLED(CONFIG_KVM)
+#define KVM_GUEST_PMI_VECTOR		0xf5
+#endif
+
  #define DEFERRED_ERROR_VECTOR		0xf4

  /* Vector on which hypervisor callbacks will be delivered */
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index f445bec516a0..0bec4c7e2308 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -157,6 +157,7 @@ static const __initconst struct idt_data apic_idts[] = {
  	INTG(POSTED_INTR_VECTOR,		asm_sysvec_kvm_posted_intr_ipi),
  	INTG(POSTED_INTR_WAKEUP_VECTOR,		asm_sysvec_kvm_posted_intr_wakeup_ipi),
  	INTG(POSTED_INTR_NESTED_VECTOR,		asm_sysvec_kvm_posted_intr_nested_ipi),
+	INTG(KVM_GUEST_PMI_VECTOR,		asm_sysvec_kvm_guest_pmi_handler),


There is a subtle inconsistency in that this code is guarded on
CONFIG_HAVE_KVM when the #define KVM_GUEST_PMI_VECTOR is guarded on
CONFIG_KVM. Beats me why there are two different flags that are so
similar, but it is possible they have different values leading to
compilation errors.

I happened to hit this compilation error because make defconfig will
define CONFIG_HAVE_KVM but not CONFIG_KVM. CONFIG_KVM is the more strict
of the two because it depends on CONFIG_HAVE_KVM.

This code should also be guarded on CONFIG_KVM.

  # endif
  # ifdef CONFIG_IRQ_WORK
  	INTG(IRQ_WORK_VECTOR,			asm_sysvec_irq_work),
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 18cd418fe106..b29714e23fc4 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -183,6 +183,12 @@ int arch_show_interrupts(struct seq_file *p, int prec)
  		seq_printf(p, "%10u ",
  			   irq_stats(j)->kvm_posted_intr_wakeup_ipis);
  	seq_puts(p, "  Posted-interrupt wakeup event\n");
+
+	seq_printf(p, "%*s: ", prec, "VPMU");
+	for_each_online_cpu(j)
+		seq_printf(p, "%10u ",
+			   irq_stats(j)->kvm_guest_pmis);
+	seq_puts(p, " KVM GUEST PMI\n");
  #endif
  #ifdef CONFIG_X86_POSTED_MSI
  	seq_printf(p, "%*s: ", prec, "PMN");
@@ -311,6 +317,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_x86_platform_ipi)
  #if IS_ENABLED(CONFIG_KVM)
  static void dummy_handler(void) {}
  static void (*kvm_posted_intr_wakeup_handler)(void) = dummy_handler;
+static void (*kvm_guest_pmi_handler)(void) = dummy_handler;

  void x86_set_kvm_irq_handler(u8 vector, void (*handler)(void))
  {
@@ -321,6 +328,10 @@ void x86_set_kvm_irq_handler(u8 vector, void (*handler)(void))
  	    (handler == dummy_handler ||
  	     kvm_posted_intr_wakeup_handler == dummy_handler))
  		kvm_posted_intr_wakeup_handler = handler;
+	else if (vector == KVM_GUEST_PMI_VECTOR &&
+		 (handler == dummy_handler ||
+		  kvm_guest_pmi_handler == dummy_handler))
+		kvm_guest_pmi_handler = handler;
  	else
  		WARN_ON_ONCE(1);

@@ -356,6 +367,16 @@ DEFINE_IDTENTRY_SYSVEC_SIMPLE(sysvec_kvm_posted_intr_nested_ipi)
  	apic_eoi();
  	inc_irq_stat(kvm_posted_intr_nested_ipis);
  }
+
+/*
+ * Handler for KVM_GUEST_PMI_VECTOR.
+ */
+DEFINE_IDTENTRY_SYSVEC(sysvec_kvm_guest_pmi_handler)
+{
+	apic_eoi();
+	inc_irq_stat(kvm_guest_pmis);
+	kvm_guest_pmi_handler();
+}
  #endif

  #ifdef CONFIG_X86_POSTED_MSI
diff --git a/tools/perf/trace/beauty/arch/x86/include/asm/irq_vectors.h b/tools/perf/trace/beauty/arch/x86/include/asm/irq_vectors.h
index 13aea8fc3d45..670dcee46631 100644
--- a/tools/perf/trace/beauty/arch/x86/include/asm/irq_vectors.h
+++ b/tools/perf/trace/beauty/arch/x86/include/asm/irq_vectors.h
@@ -77,7 +77,10 @@
   */
  #define IRQ_WORK_VECTOR			0xf6

-/* 0xf5 - unused, was UV_BAU_MESSAGE */
+#if IS_ENABLED(CONFIG_KVM)
+#define KVM_GUEST_PMI_VECTOR           0xf5
+#endif
+
  #define DEFERRED_ERROR_VECTOR		0xf4

  /* Vector on which hypervisor callbacks will be delivered */




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