From: David Woodhouse <dwmw2@infradead.org>
To: kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Sean Christopherson <seanjc@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Paul Durrant <paul@xen.org>, Shuah Khan <shuah@kernel.org>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org,
Oliver Upton <oliver.upton@linux.dev>,
Marcelo Tosatti <mtosatti@redhat.com>,
jalliste@amazon.co.uk, sveith@amazon.de
Subject: [PATCH 07/10] KVM: x86: Avoid NTP frequency skew for KVM clock on 32-bit host
Date: Thu, 18 Apr 2024 20:34:46 +0100 [thread overview]
Message-ID: <20240418193528.41780-8-dwmw2@infradead.org> (raw)
In-Reply-To: <20240418193528.41780-1-dwmw2@infradead.org>
From: David Woodhouse <dwmw@amazon.co.uk>
Commit 53fafdbb8b21 ("KVM: x86: switch KVMCLOCK base to monotonic raw
clock") did so only for 64-bit hosts, by capturing the boot offset from
within the existing clocksource notifier update_pvclock_gtod().
That notifier was added in commit 16e8d74d2da9 ("KVM: x86: notifier for
clocksource changes") but only on x86_64, because its original purpose
was just to disable the "master clock" mode which is only supported on
x86_64.
Now that the notifier is used for more than disabling master clock mode,
(well, OK, more than a decade later but clocks are hard), enable it for
the 32-bit build too so that get_kvmclock_base_ns() can be unaffected by
NTP sync on 32-bit too.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
arch/x86/kvm/x86.c | 18 ++++++------------
1 file changed, 6 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 00a7c1188dec..44b3d2a0da5b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2245,7 +2245,6 @@ static int do_set_msr(struct kvm_vcpu *vcpu, unsigned index, u64 *data)
return kvm_set_msr_ignored_check(vcpu, index, *data, true);
}
-#ifdef CONFIG_X86_64
struct pvclock_clock {
int vclock_mode;
u64 cycle_last;
@@ -2303,13 +2302,6 @@ static s64 get_kvmclock_base_ns(void)
/* Count up from boot time, but with the frequency of the raw clock. */
return ktime_to_ns(ktime_add(ktime_get_raw(), pvclock_gtod_data.offs_boot));
}
-#else
-static s64 get_kvmclock_base_ns(void)
-{
- /* Master clock not used, so we can just use CLOCK_BOOTTIME. */
- return ktime_get_boottime_ns();
-}
-#endif
static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock, int sec_hi_ofs)
{
@@ -9819,6 +9811,7 @@ static void pvclock_irq_work_fn(struct irq_work *w)
}
static DEFINE_IRQ_WORK(pvclock_irq_work, pvclock_irq_work_fn);
+#endif
/*
* Notification about pvclock gtod data update.
@@ -9826,26 +9819,26 @@ static DEFINE_IRQ_WORK(pvclock_irq_work, pvclock_irq_work_fn);
static int pvclock_gtod_notify(struct notifier_block *nb, unsigned long unused,
void *priv)
{
- struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
struct timekeeper *tk = priv;
update_pvclock_gtod(tk);
+#ifdef CONFIG_X86_64
/*
* Disable master clock if host does not trust, or does not use,
* TSC based clocksource. Delegate queue_work() to irq_work as
* this is invoked with tk_core.seq write held.
*/
- if (!gtod_is_based_on_tsc(gtod->clock.vclock_mode) &&
+ if (!gtod_is_based_on_tsc(pvclock_gtod_data.clock.vclock_mode) &&
atomic_read(&kvm_guest_has_master_clock) != 0)
irq_work_queue(&pvclock_irq_work);
+#endif
return 0;
}
static struct notifier_block pvclock_gtod_notifier = {
.notifier_call = pvclock_gtod_notify,
};
-#endif
static inline void kvm_ops_update(struct kvm_x86_init_ops *ops)
{
@@ -9984,9 +9977,10 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
if (pi_inject_timer == -1)
pi_inject_timer = housekeeping_enabled(HK_TYPE_TIMER);
-#ifdef CONFIG_X86_64
+
pvclock_gtod_register_notifier(&pvclock_gtod_notifier);
+#ifdef CONFIG_X86_64
if (hypervisor_is_type(X86_HYPER_MS_HYPERV))
set_hv_tscchange_cb(kvm_hyperv_tsc_notifier);
#endif
--
2.44.0
next prev parent reply other threads:[~2024-04-18 19:35 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-18 19:34 [RFC PATCH 0/10] Cleaning up the KVM clock mess David Woodhouse
2024-04-18 19:34 ` [PATCH 01/10] KVM: x86/xen: Do not corrupt KVM clock in kvm_xen_shared_info_init() David Woodhouse
2024-04-18 19:34 ` [PATCH 02/10] KVM: x86: Improve accuracy of KVM clock when TSC scaling is in force David Woodhouse
2024-04-19 15:29 ` Paul Durrant
2024-04-22 12:22 ` Paolo Bonzini
2024-04-22 15:39 ` David Woodhouse
2024-04-22 15:54 ` Paolo Bonzini
2024-04-22 16:44 ` David Woodhouse
2024-04-18 19:34 ` [PATCH 03/10] KVM: x86: Add KVM_[GS]ET_CLOCK_GUEST for accurate KVM clock migration David Woodhouse
2024-04-19 15:40 ` Paul Durrant
2024-04-19 15:49 ` David Woodhouse
2024-04-22 14:11 ` Paolo Bonzini
2024-04-22 15:02 ` David Woodhouse
2024-04-18 19:34 ` [PATCH 04/10] KVM: selftests: Add KVM/PV clock selftest to prove timer correction David Woodhouse
2024-04-19 15:44 ` Paul Durrant
2024-04-18 19:34 ` [PATCH 05/10] KVM: x86: Explicitly disable TSC scaling without CONSTANT_TSC David Woodhouse
2024-04-19 15:45 ` Paul Durrant
2024-04-18 19:34 ` [PATCH 06/10] KVM: x86: Add KVM_VCPU_TSC_SCALE and fix the documentation on TSC migration David Woodhouse
2024-04-19 15:49 ` Paul Durrant
2024-04-19 15:53 ` David Woodhouse
2024-04-18 19:34 ` David Woodhouse [this message]
2024-04-19 15:53 ` [PATCH 07/10] KVM: x86: Avoid NTP frequency skew for KVM clock on 32-bit host Paul Durrant
2024-04-18 19:34 ` [PATCH 08/10] KVM: x86: Remove periodic global clock updates David Woodhouse
2024-04-19 15:55 ` Paul Durrant
2024-04-18 19:34 ` [PATCH 09/10] KVM: x86: Kill KVM_REQ_GLOBAL_CLOCK_UPDATE David Woodhouse
2024-04-19 15:57 ` Paul Durrant
2024-04-18 19:34 ` [PATCH 10/10] KVM: x86: Fix KVM clock precision in __get_kvmclock() David Woodhouse
2024-04-19 16:07 ` Paul Durrant
2024-04-19 12:51 ` [PATCH 11/10] KVM: x86: Fix software TSC upscaling in kvm_update_guest_time() David Woodhouse
2024-04-19 12:52 ` [RFC PATCH 0/10] Cleaning up the KVM clock mess David Woodhouse
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