KVM: Handle async PF in a guest.

When async PF capability is detected hook up special page fault handler
that will handle async page fault events and bypass other page faults to
regular page fault handler. Also add async PF handling to nested SVM
emulation. Async PF always generates exit to L1 where vcpu thread will
be scheduled out until page is available.

Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

2 files changed, 13 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 2315398..fbfd367 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -65,6 +65,9 @@ struct kvm_mmu_op_release_pt {
 	__u64 pt_phys;
 };
 
+#define KVM_PV_REASON_PAGE_NOT_PRESENT 1
+#define KVM_PV_REASON_PAGE_READY 2
+
 struct kvm_vcpu_pv_apf_data {
 	__u32 reason;
 	__u8 pad[60];
@@ -171,8 +174,17 @@ static inline unsigned int kvm_arch_para_features(void)
 
 #ifdef CONFIG_KVM_GUEST
 void __init kvm_guest_init(void);
+void kvm_async_pf_task_wait(u32 token);
+void kvm_async_pf_task_wake(u32 token);
+u32 kvm_read_and_reset_pf_reason(void);
 #else
 #define kvm_guest_init() do { } while (0)
+#define kvm_async_pf_task_wait(T) do {} while(0)
+#define kvm_async_pf_task_wake(T) do {} while(0)
+static u32 kvm_read_and_reset_pf_reason(void)
+{
+	return 0;
+}
 #endif
 
 #endif /* __KERNEL__ */
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index f66cda5..0310da6 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -30,6 +30,7 @@ asmlinkage void segment_not_present(void);
 asmlinkage void stack_segment(void);
 asmlinkage void general_protection(void);
 asmlinkage void page_fault(void);
+asmlinkage void async_page_fault(void);
 asmlinkage void spurious_interrupt_bug(void);
 asmlinkage void coprocessor_error(void);
 asmlinkage void alignment_check(void);