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Message-Id: <20190920062713.78503-2-suleiman@google.com>
Date: Fri, 20 Sep 2019 15:27:12 +0900
From: Suleiman Souhlal <suleiman@...gle.com>
To: pbonzini@...hat.com, rkrcmar@...hat.com, tglx@...utronix.de
Cc: john.stultz@...aro.org, sboyd@...nel.org,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
Suleiman Souhlal <suleiman@...gle.com>
Subject: [RFC 1/2] kvm: Mechanism to copy host timekeeping parameters into guest.
This is used to synchronize time between host and guest.
The guest can request the (guest) physical address it wants the
data in through the MSR_KVM_TIMEKEEPER_EN MSR.
We maintain a shadow copy of the timekeeper that gets updated
whenever the timekeeper gets updated, and then copied into the
guest.
It currently assumes the host timekeeper is "tsc".
Signed-off-by: Suleiman Souhlal <suleiman@...gle.com>
---
arch/x86/include/asm/kvm_host.h | 3 +
arch/x86/include/asm/pvclock-abi.h | 27 ++++++
arch/x86/include/uapi/asm/kvm_para.h | 1 +
arch/x86/kvm/x86.c | 121 +++++++++++++++++++++++++++
4 files changed, 152 insertions(+)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index bdc16b0aa7c6..b1b4c3a80b8d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -666,7 +666,10 @@ struct kvm_vcpu_arch {
struct pvclock_vcpu_time_info hv_clock;
unsigned int hw_tsc_khz;
struct gfn_to_hva_cache pv_time;
+ struct gfn_to_hva_cache pv_timekeeper_g2h;
+ struct pvclock_timekeeper pv_timekeeper;
bool pv_time_enabled;
+ bool pv_timekeeper_enabled;
/* set guest stopped flag in pvclock flags field */
bool pvclock_set_guest_stopped_request;
diff --git a/arch/x86/include/asm/pvclock-abi.h b/arch/x86/include/asm/pvclock-abi.h
index 1436226efe3e..2809008b9b26 100644
--- a/arch/x86/include/asm/pvclock-abi.h
+++ b/arch/x86/include/asm/pvclock-abi.h
@@ -40,6 +40,33 @@ struct pvclock_wall_clock {
u32 nsec;
} __attribute__((__packed__));
+struct pvclock_read_base {
+ u64 mask;
+ u64 cycle_last;
+ u32 mult;
+ u32 shift;
+ u64 xtime_nsec;
+ u64 base;
+} __attribute__((__packed__));
+
+struct pvclock_timekeeper {
+ u64 gen;
+ u64 flags;
+ struct pvclock_read_base tkr_mono;
+ struct pvclock_read_base tkr_raw;
+ u64 xtime_sec;
+ u64 ktime_sec;
+ u64 wall_to_monotonic_sec;
+ u64 wall_to_monotonic_nsec;
+ u64 offs_real;
+ u64 offs_boot;
+ u64 offs_tai;
+ u64 raw_sec;
+ u64 tsc_offset;
+} __attribute__((__packed__));
+
+#define PVCLOCK_TIMEKEEPER_ENABLED (1 << 0)
+
#define PVCLOCK_TSC_STABLE_BIT (1 << 0)
#define PVCLOCK_GUEST_STOPPED (1 << 1)
/* PVCLOCK_COUNTS_FROM_ZERO broke ABI and can't be used anymore. */
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 2a8e0b6b9805..3ebb1d87db3a 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -50,6 +50,7 @@
#define MSR_KVM_STEAL_TIME 0x4b564d03
#define MSR_KVM_PV_EOI_EN 0x4b564d04
#define MSR_KVM_POLL_CONTROL 0x4b564d05
+#define MSR_KVM_TIMEKEEPER_EN 0x4b564d06
struct kvm_steal_time {
__u64 steal;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 91602d310a3f..06a940a74005 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -157,6 +157,8 @@ module_param(force_emulation_prefix, bool, S_IRUGO);
int __read_mostly pi_inject_timer = -1;
module_param(pi_inject_timer, bint, S_IRUGO | S_IWUSR);
+static atomic_t pv_timekeepers_nr;
+
#define KVM_NR_SHARED_MSRS 16
struct kvm_shared_msrs_global {
@@ -2621,6 +2623,16 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
break;
}
+ case MSR_KVM_TIMEKEEPER_EN:
+ if (kvm_gfn_to_hva_cache_init(vcpu->kvm,
+ &vcpu->arch.pv_timekeeper_g2h, data,
+ sizeof(struct pvclock_timekeeper)))
+ vcpu->arch.pv_timekeeper_enabled = false;
+ else {
+ vcpu->arch.pv_timekeeper_enabled = true;
+ atomic_inc(&pv_timekeepers_nr);
+ }
+ break;
case MSR_KVM_ASYNC_PF_EN:
if (kvm_pv_enable_async_pf(vcpu, data))
return 1;
@@ -6965,6 +6977,109 @@ static struct perf_guest_info_callbacks kvm_guest_cbs = {
.handle_intel_pt_intr = kvm_handle_intel_pt_intr,
};
+static DEFINE_SPINLOCK(shadow_pvtk_lock);
+static struct pvclock_timekeeper shadow_pvtk;
+
+static void
+pvclock_copy_read_base(struct pvclock_read_base *pvtkr,
+ struct tk_read_base *tkr)
+{
+ pvtkr->cycle_last = tkr->cycle_last;
+ pvtkr->mult = tkr->mult;
+ pvtkr->shift = tkr->shift;
+ pvtkr->mask = tkr->mask;
+ pvtkr->xtime_nsec = tkr->xtime_nsec;
+ pvtkr->base = tkr->base;
+}
+
+static void
+kvm_copy_into_pvtk(struct kvm_vcpu *vcpu)
+{
+ struct pvclock_timekeeper *pvtk;
+ unsigned long flags;
+
+ if (!vcpu->arch.pv_timekeeper_enabled)
+ return;
+
+ pvtk = &vcpu->arch.pv_timekeeper;
+ if (pvclock_gtod_data.clock.vclock_mode == VCLOCK_TSC) {
+ pvtk->flags |= PVCLOCK_TIMEKEEPER_ENABLED;
+ spin_lock_irqsave(&shadow_pvtk_lock, flags);
+ pvtk->tkr_mono = shadow_pvtk.tkr_mono;
+ pvtk->tkr_raw = shadow_pvtk.tkr_raw;
+
+ pvtk->xtime_sec = shadow_pvtk.xtime_sec;
+ pvtk->ktime_sec = shadow_pvtk.ktime_sec;
+ pvtk->wall_to_monotonic_sec =
+ shadow_pvtk.wall_to_monotonic_sec;
+ pvtk->wall_to_monotonic_nsec =
+ shadow_pvtk.wall_to_monotonic_nsec;
+ pvtk->offs_real = shadow_pvtk.offs_real;
+ pvtk->offs_boot = shadow_pvtk.offs_boot;
+ pvtk->offs_tai = shadow_pvtk.offs_tai;
+ pvtk->raw_sec = shadow_pvtk.raw_sec;
+ spin_unlock_irqrestore(&shadow_pvtk_lock, flags);
+
+ pvtk->tsc_offset = kvm_x86_ops->read_l1_tsc_offset(vcpu);
+ } else
+ pvtk->flags &= ~PVCLOCK_TIMEKEEPER_ENABLED;
+
+ BUILD_BUG_ON(offsetof(struct pvclock_timekeeper, gen) != 0);
+
+ /*
+ * Make the gen count odd to indicate we are in the process of
+ * updating.
+ */
+ vcpu->arch.pv_timekeeper.gen++;
+ vcpu->arch.pv_timekeeper.gen |= 1;
+
+ /*
+ * See comment in kvm_guest_time_update() for why we have to do
+ * multiple writes.
+ */
+ kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.pv_timekeeper_g2h,
+ &vcpu->arch.pv_timekeeper, sizeof(vcpu->arch.pv_timekeeper.gen));
+
+ smp_wmb();
+
+ kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.pv_timekeeper_g2h,
+ &vcpu->arch.pv_timekeeper, sizeof(vcpu->arch.pv_timekeeper));
+
+ smp_wmb();
+
+ vcpu->arch.pv_timekeeper.gen++;
+
+ kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.pv_timekeeper_g2h,
+ &vcpu->arch.pv_timekeeper, sizeof(vcpu->arch.pv_timekeeper.gen));
+}
+
+static void
+update_shadow_pvtk(struct timekeeper *tk)
+{
+ struct pvclock_timekeeper *pvtk;
+ unsigned long flags;
+
+ pvtk = &shadow_pvtk;
+
+ if (atomic_read(&pv_timekeepers_nr) == 0 ||
+ pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
+ return;
+
+ spin_lock_irqsave(&shadow_pvtk_lock, flags);
+ pvclock_copy_read_base(&pvtk->tkr_mono, &tk->tkr_mono);
+ pvclock_copy_read_base(&pvtk->tkr_raw, &tk->tkr_raw);
+
+ pvtk->xtime_sec = tk->xtime_sec;
+ pvtk->ktime_sec = tk->ktime_sec;
+ pvtk->wall_to_monotonic_sec = tk->wall_to_monotonic.tv_sec;
+ pvtk->wall_to_monotonic_nsec = tk->wall_to_monotonic.tv_nsec;
+ pvtk->offs_real = tk->offs_real;
+ pvtk->offs_boot = tk->offs_boot;
+ pvtk->offs_tai = tk->offs_tai;
+ pvtk->raw_sec = tk->raw_sec;
+ spin_unlock_irqrestore(&shadow_pvtk_lock, flags);
+}
+
#ifdef CONFIG_X86_64
static void pvclock_gtod_update_fn(struct work_struct *work)
{
@@ -6993,6 +7108,7 @@ static int pvclock_gtod_notify(struct notifier_block *nb, unsigned long unused,
struct timekeeper *tk = priv;
update_pvclock_gtod(tk);
+ update_shadow_pvtk(tk);
/* disable master clock if host does not trust, or does not
* use, TSC based clocksource.
@@ -7809,6 +7925,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
bool req_immediate_exit = false;
+ kvm_copy_into_pvtk(vcpu);
+
if (kvm_request_pending(vcpu)) {
if (kvm_check_request(KVM_REQ_GET_VMCS12_PAGES, vcpu))
kvm_x86_ops->get_vmcs12_pages(vcpu);
@@ -8891,6 +9009,9 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
kvmclock_reset(vcpu);
+ if (vcpu->arch.pv_timekeeper_enabled)
+ atomic_dec(&pv_timekeepers_nr);
+
kvm_x86_ops->vcpu_free(vcpu);
free_cpumask_var(wbinvd_dirty_mask);
}
--
2.23.0.237.gc6a4ce50a0-goog
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