KVM: Halt vcpu if page it tries to access is swapped out

If a guest accesses swapped out memory do not swap it in from vcpu thread
context. Schedule work to do swapping and put vcpu into halted state
instead.

Interrupts will still be delivered to the guest and if interrupt will
cause reschedule guest will continue to run another task.

[avi: remove call to get_user_pages_noio(), nacked by Linus; this
      makes everything synchrnous again]

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

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f702f82aa1eb..b5f4c1a36d65 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -83,11 +83,14 @@
 #define KVM_NR_FIXED_MTRR_REGION 88
 #define KVM_NR_VAR_MTRR 8
 
+#define ASYNC_PF_PER_VCPU 64
+
 extern spinlock_t kvm_lock;
 extern struct list_head vm_list;
 
 struct kvm_vcpu;
 struct kvm;
+struct kvm_async_pf;
 
 enum kvm_reg {
 	VCPU_REGS_RAX = 0,
@@ -412,6 +415,11 @@ struct kvm_vcpu_arch {
 	u64 hv_vapic;
 
 	cpumask_var_t wbinvd_dirty_mask;
+
+	struct {
+		bool halted;
+		gfn_t gfns[roundup_pow_of_two(ASYNC_PF_PER_VCPU)];
+	} apf;
 };
 
 struct kvm_arch {
@@ -585,6 +593,10 @@ struct kvm_x86_ops {
 	const struct trace_print_flags *exit_reasons_str;
 };
 
+struct kvm_arch_async_pf {
+	gfn_t gfn;
+};
+
 extern struct kvm_x86_ops *kvm_x86_ops;
 
 int kvm_mmu_module_init(void);
@@ -799,4 +811,10 @@ void kvm_set_shared_msr(unsigned index, u64 val, u64 mask);
 
 bool kvm_is_linear_rip(struct kvm_vcpu *vcpu, unsigned long linear_rip);
 
+void kvm_arch_async_page_not_present(struct kvm_vcpu *vcpu,
+				     struct kvm_async_pf *work);
+void kvm_arch_async_page_present(struct kvm_vcpu *vcpu,
+				 struct kvm_async_pf *work);
+extern bool kvm_find_async_pf_gfn(struct kvm_vcpu *vcpu, gfn_t gfn);
+
 #endif /* _ASM_X86_KVM_HOST_H */