Re: [RFC PATCH V4 13/17] x86/sev: Add Check of #HV event in path

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Hi Tianyu,


Add check_hv_pending() and check_hv_pending_after_irq() to
check queued #HV event when irq is disabled.

Signed-off-by: Tianyu Lan <tiala@xxxxxxxxxxxxx>
---
  arch/x86/entry/entry_64.S       | 18 ++++++++++++++++
  arch/x86/include/asm/irqflags.h | 11 ++++++++++
  arch/x86/kernel/sev.c           | 38 +++++++++++++++++++++++++++++++++
  3 files changed, 67 insertions(+)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index d877774c3141..efa56dfde19e 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1073,6 +1073,15 @@ SYM_CODE_END(paranoid_entry)
   * R15 - old SPEC_CTRL
   */
  SYM_CODE_START_LOCAL(paranoid_exit)
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+	/*
+	 * If a #HV was delivered during execution and interrupts were
+	 * disabled, then check if it can be handled before the iret
+	 * (which may re-enable interrupts).
+	 */
+	mov     %rsp, %rdi
+	call    check_hv_pending
+#endif
  	UNWIND_HINT_REGS
/*
@@ -1197,6 +1206,15 @@ SYM_CODE_START(error_entry)
  SYM_CODE_END(error_entry)
SYM_CODE_START_LOCAL(error_return)
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+	/*
+	 * If a #HV was delivered during execution and interrupts were
+	 * disabled, then check if it can be handled before the iret
+	 * (which may re-enable interrupts).
+	 */
+	mov     %rsp, %rdi
+	call    check_hv_pending
+#endif
  	UNWIND_HINT_REGS
  	DEBUG_ENTRY_ASSERT_IRQS_OFF
  	testb	$3, CS(%rsp)
diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
index 8c5ae649d2df..8368e3fe2d36 100644
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -11,6 +11,10 @@
  /*
   * Interrupt control:
   */
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+void check_hv_pending(struct pt_regs *regs);
+void check_hv_pending_irq_enable(void);
+#endif
/* Declaration required for gcc < 4.9 to prevent -Werror=missing-prototypes */
  extern inline unsigned long native_save_fl(void);
@@ -40,12 +44,19 @@ static __always_inline void native_irq_disable(void)
  static __always_inline void native_irq_enable(void)
  {
  	asm volatile("sti": : :"memory");
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+	check_hv_pending_irq_enable();
+#endif
  }
static __always_inline void native_safe_halt(void)
  {
  	mds_idle_clear_cpu_buffers();
  	asm volatile("sti; hlt": : :"memory");

I was able to boot the Linux guest on KVM SNP host with below [1]
change above your patch series.

Thanks,
Pankaj

[1]
diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
index 8368e3fe2d36..df993bec56c4 100644
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -52,11 +52,13 @@ static __always_inline void native_irq_enable(void)
 static __always_inline void native_safe_halt(void)
 {
        mds_idle_clear_cpu_buffers();
-       asm volatile("sti; hlt": : :"memory");
+       asm volatile("sti": : :"memory");

 #ifdef CONFIG_AMD_MEM_ENCRYPT
        check_hv_pending_irq_enable();
 #endif
+       asm volatile("hlt": : :"memory");
 }



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