[RFC PATCH v3 5/5] kvm/x86: virtual suspend time injection: Implement guest side

[Hikaru Nishida <hikalium@chromium.org>]

Add guest side implementation of KVM virtual suspend time injection.

How it works from guest's view:
- Guest will be paused without going through suspend/resume path in the
  guest kernel
- Before resuming the execution of the guest's vcpus, host will adjust
  the hardware clock (and kvm_clock) to the time before the suspend.
  - By this action, guest's CLOCK_MONOTONIC behaves as expected (stops
    during the host's suspension.)
- the guest will receive an IRQ from the guest that notifies about the
  suspend which was invisible to the guest. In the handler, the guest
  can adjust their CLOCK_BOOTTIME to reflect the suspension.
  - Now, CLOCK_BOOTTIME includes the time passed during the host's
    suspension.

Signed-off-by: Hikaru Nishida <hikalium@chromium.org>
---

Changes in v3:
- Reused HYPERVISOR_CALLBACK_VECTOR IRQ instead of adding a new one.
- Extracted arch-independent parts.

 arch/x86/Kconfig                    | 13 ++++++++
 arch/x86/include/asm/idtentry.h     |  2 +-
 arch/x86/include/asm/kvmclock.h     |  9 ++++++
 arch/x86/kernel/kvm.c               | 14 ++++++---
 arch/x86/kernel/kvmclock.c          | 26 ++++++++++++++++
 arch/x86/mm/fault.c                 |  2 +-
 include/linux/timekeeper_internal.h |  5 ++++
 include/linux/timekeeping.h         |  4 +++
 kernel/time/timekeeping.c           | 46 +++++++++++++++++++++++++++++
 9 files changed, 115 insertions(+), 6 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d9830e7e1060..1d4a529d1577 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -824,6 +824,19 @@ config KVM_GUEST
 	  underlying device model, the host provides the guest with
 	  timing infrastructure such as time of day, and system time
 
+config KVM_VIRT_SUSPEND_TIMING_GUEST
+	bool "Guest support for virtual suspend time injection"
+	depends on KVM_GUEST
+	default n
+	help
+	 This option makes the host's suspension reflected on the guest's clocks.
+	 In other words, guest's CLOCK_MONOTONIC will stop and
+	 CLOCK_BOOTTIME keeps running during the host's suspension.
+	 This feature will only be effective when both guest and host support
+	 this feature. For the host side, see KVM_VIRT_SUSPEND_TIMING.
+
+	 If unsure, say N.
+
 config ARCH_CPUIDLE_HALTPOLL
 	def_bool n
 	prompt "Disable host haltpoll when loading haltpoll driver"
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index 1345088e9902..5e30f84ea07e 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -686,7 +686,7 @@ DECLARE_IDTENTRY_SYSVEC(HYPERVISOR_CALLBACK_VECTOR,	sysvec_xen_hvm_callback);
 #endif
 
 #ifdef CONFIG_KVM_GUEST
-DECLARE_IDTENTRY_SYSVEC(HYPERVISOR_CALLBACK_VECTOR,	sysvec_kvm_asyncpf_interrupt);
+DECLARE_IDTENTRY_SYSVEC(HYPERVISOR_CALLBACK_VECTOR,	sysvec_kvm_hv_callback);
 #endif
 
 #undef X86_TRAP_OTHER
diff --git a/arch/x86/include/asm/kvmclock.h b/arch/x86/include/asm/kvmclock.h
index 9add14edc24d..2bf1a5c92319 100644
--- a/arch/x86/include/asm/kvmclock.h
+++ b/arch/x86/include/asm/kvmclock.h
@@ -20,4 +20,13 @@ static inline struct pvclock_vsyscall_time_info *this_cpu_hvclock(void)
 	return this_cpu_read(hv_clock_per_cpu);
 }
 
+#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING_GUEST
+u64 kvm_get_suspend_time(void);
+#else
+static inline u64 kvm_get_suspend_time(void)
+{
+	return 0;
+}
+#endif
+
 #endif /* _ASM_X86_KVM_CLOCK_H */
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index b656456c3a94..3d84ef6d9df2 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -40,6 +40,7 @@
 #include <asm/ptrace.h>
 #include <asm/reboot.h>
 #include <asm/svm.h>
+#include <asm/kvmclock.h>
 
 DEFINE_STATIC_KEY_FALSE(kvm_async_pf_enabled);
 
@@ -270,7 +271,7 @@ noinstr bool __kvm_handle_async_pf(struct pt_regs *regs, u32 token)
 	return true;
 }
 
-DEFINE_IDTENTRY_SYSVEC(sysvec_kvm_asyncpf_interrupt)
+DEFINE_IDTENTRY_SYSVEC(sysvec_kvm_hv_callback)
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
 	u32 token;
@@ -286,6 +287,8 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_kvm_asyncpf_interrupt)
 		wrmsrl(MSR_KVM_ASYNC_PF_ACK, 1);
 	}
 
+	timekeeping_inject_virtual_suspend_time(kvm_get_suspend_time());
+
 	set_irq_regs(old_regs);
 }
 
@@ -710,10 +713,13 @@ static void __init kvm_guest_init(void)
 	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
 		apic_set_eoi_write(kvm_guest_apic_eoi_write);
 
-	if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT) && kvmapf) {
+	if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT) && kvmapf)
 		static_branch_enable(&kvm_async_pf_enabled);
-		alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, asm_sysvec_kvm_asyncpf_interrupt);
-	}
+
+	if ((kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT) && kvmapf) ||
+	    kvm_para_has_feature(KVM_FEATURE_HOST_SUSPEND_TIME))
+		alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR,
+				asm_sysvec_kvm_hv_callback);
 
 #ifdef CONFIG_SMP
 	if (pv_tlb_flush_supported()) {
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 73c74b961d0f..3e16d0ab79f3 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -16,11 +16,15 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/set_memory.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
 
 #include <asm/hypervisor.h>
 #include <asm/mem_encrypt.h>
 #include <asm/x86_init.h>
 #include <asm/kvmclock.h>
+#include <asm/desc.h>
+#include <asm/idtentry.h>
 
 static int kvmclock __initdata = 1;
 static int kvmclock_vsyscall __initdata = 1;
@@ -48,6 +52,9 @@ early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
 
 static struct pvclock_vsyscall_time_info
 			hv_clock_boot[HVC_BOOT_ARRAY_SIZE] __bss_decrypted __aligned(PAGE_SIZE);
+#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING_GUEST
+static struct kvm_suspend_time suspend_time __bss_decrypted;
+#endif
 static struct pvclock_wall_clock wall_clock __bss_decrypted;
 static struct pvclock_vsyscall_time_info *hvclock_mem;
 DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu);
@@ -281,6 +288,17 @@ static int kvmclock_setup_percpu(unsigned int cpu)
 	return p ? 0 : -ENOMEM;
 }
 
+#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING_GUEST
+/**
+ * kvm_get_suspend_time - duration of host suspend.
+ * Return: Cumulative duration of host suspend in nanoseconds.
+ */
+u64 kvm_get_suspend_time(void)
+{
+	return suspend_time.suspend_time_ns;
+}
+#endif
+
 void __init kvmclock_init(void)
 {
 	u8 flags;
@@ -295,6 +313,14 @@ void __init kvmclock_init(void)
 		return;
 	}
 
+#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING_GUEST
+	if (kvm_para_has_feature(KVM_FEATURE_HOST_SUSPEND_TIME)) {
+		/* Register the suspend time structure */
+		wrmsrl(MSR_KVM_HOST_SUSPEND_TIME,
+		       slow_virt_to_phys(&suspend_time) | KVM_MSR_ENABLED);
+	}
+#endif
+
 	if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
 			      kvmclock_setup_percpu, NULL) < 0) {
 		return;
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 84a2c8c4af73..f36f49585d5d 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1509,7 +1509,7 @@ DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
 	 * memory is swapped out). Note, the corresponding "page ready" event
 	 * which is injected when the memory becomes available, is delivered via
 	 * an interrupt mechanism and not a #PF exception
-	 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()).
+	 * (see arch/x86/kernel/kvm.c: sysvec_kvm_hv_callback()).
 	 *
 	 * We are relying on the interrupted context being sane (valid RSP,
 	 * relevant locks not held, etc.), which is fine as long as the
diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h
index 84ff2844df2a..0d5b29122d40 100644
--- a/include/linux/timekeeper_internal.h
+++ b/include/linux/timekeeper_internal.h
@@ -68,6 +68,8 @@ struct tk_read_base {
  *			shifted nano seconds.
  * @ntp_error_shift:	Shift conversion between clock shifted nano seconds and
  *			ntp shifted nano seconds.
+ * @kvm_suspend_time:	The cumulative duration of suspend injected through KVM
+ *			in nano seconds.
  * @last_warning:	Warning ratelimiter (DEBUG_TIMEKEEPING)
  * @underflow_seen:	Underflow warning flag (DEBUG_TIMEKEEPING)
  * @overflow_seen:	Overflow warning flag (DEBUG_TIMEKEEPING)
@@ -124,6 +126,9 @@ struct timekeeper {
 	u32			ntp_err_mult;
 	/* Flag used to avoid updating NTP twice with same second */
 	u32			skip_second_overflow;
+#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING_GUEST
+	u64			kvm_suspend_time;
+#endif
 #ifdef CONFIG_DEBUG_TIMEKEEPING
 	long			last_warning;
 	/*
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index f7be69c81dab..a2228300c3f9 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -310,4 +310,8 @@ void read_persistent_wall_and_boot_offset(struct timespec64 *wall_clock,
 extern int update_persistent_clock64(struct timespec64 now);
 #endif
 
+#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING_GUEST
+void timekeeping_inject_virtual_suspend_time(u64 total_duration_ns);
+#endif
+
 #endif
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e77580d9f8c1..5f474cde0bae 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -2133,6 +2133,52 @@ static u64 logarithmic_accumulation(struct timekeeper *tk, u64 offset,
 	return offset;
 }
 
+#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING_GUEST
+/**
+ * timekeeping_inject_virtual_suspend_time - Inject virtual suspend time
+ * when requested by the kvm host.
+ * @total_duration_ns:	Total suspend time to be injected in nanoseconds.
+ */
+void timekeeping_inject_virtual_suspend_time(u64 total_duration_ns)
+{
+	struct timekeeper *tk = &tk_core.timekeeper;
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&timekeeper_lock, flags);
+	if (total_duration_ns > tk->kvm_suspend_time) {
+		/*
+		 * Do injection only if the time is not injected yet.
+		 * total_duration_ns and tk->kvm_suspend_time values are
+		 * cumulative, so the delta between them will be an amount
+		 * of adjustments. For example, if the host suspends 2 times
+		 * during the guest is running and each suspend is 5 seconds,
+		 * total_duration_ns will be 5 seconds at the first injection
+		 * and tk->kvm_suspend_time was initialized to zero so the
+		 * adjustment injected here will be 5 - 0 = 5 seconds and
+		 * tk->kvm_suspend_time will be updated to 5 seconds.
+		 * On the second injection after the second resume,
+		 * total_duration_ns will be 10 seconds and
+		 * tk->kvm_suspend_time will be 5 seconds so 10 - 5 = 5 seconds
+		 * of the suspend time will be injected again.
+		 */
+		struct timespec64 delta =
+			ns_to_timespec64(total_duration_ns -
+					 tk->kvm_suspend_time);
+		tk->kvm_suspend_time = total_duration_ns;
+
+		write_seqcount_begin(&tk_core.seq);
+		timekeeping_forward_now(tk);
+		__timekeeping_inject_sleeptime(tk, &delta);
+		timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
+		write_seqcount_end(&tk_core.seq);
+
+		/* signal hrtimers about time change */
+		clock_was_set_delayed();
+	}
+	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+}
+#endif
+
 /*
  * timekeeping_advance - Updates the timekeeper to the current time and
  * current NTP tick length
-- 
2.33.0.1079.g6e70778dc9-goog