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authorVitaly Kuznetsov <vkuznets@redhat.com>2018-01-24 14:23:33 +0100
committerThomas Gleixner <tglx@linutronix.de>2018-01-30 23:55:32 +0100
commit93286261de1b46339aa27cd4c639b21778f6cade (patch)
treeef94c61bab5e38bb42aee854d7babc4ece8c7de5 /arch/x86/hyperv
parente2768eaa1ca4fbb7b778da5615cce3dd310352e6 (diff)
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x86/hyperv: Reenlightenment notifications support
Hyper-V supports Live Migration notification. This is supposed to be used in conjunction with TSC emulation: when a VM is migrated to a host with different TSC frequency for some short period the host emulates the accesses to TSC and sends an interrupt to notify about the event. When the guest is done updating everything it can disable TSC emulation and everything will start working fast again. These notifications weren't required until now as Hyper-V guests are not supposed to use TSC as a clocksource: in Linux the TSC is even marked as unstable on boot. Guests normally use 'tsc page' clocksource and host updates its values on migrations automatically. Things change when with nested virtualization: even when the PV clocksources (kvm-clock or tsc page) are passed through to the nested guests the TSC frequency and frequency changes need to be know.. Hyper-V Top Level Functional Specification (as of v5.0b) wrongly specifies EAX:BIT(12) of CPUID:0x40000009 as the feature identification bit. The right one to check is EAX:BIT(13) of CPUID:0x40000003. I was assured that the fix in on the way. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: kvm@vger.kernel.org Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com> Cc: Roman Kagan <rkagan@virtuozzo.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: devel@linuxdriverproject.org Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Cathy Avery <cavery@redhat.com> Cc: Mohammed Gamal <mmorsy@redhat.com> Link: https://lkml.kernel.org/r/20180124132337.30138-4-vkuznets@redhat.com
Diffstat (limited to 'arch/x86/hyperv')
-rw-r--r--arch/x86/hyperv/hv_init.c89
1 files changed, 89 insertions, 0 deletions
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 1a6c63f721bc..712ac40081f7 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -18,6 +18,8 @@
*/
#include <linux/types.h>
+#include <asm/apic.h>
+#include <asm/desc.h>
#include <asm/hypervisor.h>
#include <asm/hyperv.h>
#include <asm/mshyperv.h>
@@ -102,6 +104,93 @@ static int hv_cpu_init(unsigned int cpu)
return 0;
}
+static void (*hv_reenlightenment_cb)(void);
+
+static void hv_reenlightenment_notify(struct work_struct *dummy)
+{
+ struct hv_tsc_emulation_status emu_status;
+
+ rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);
+
+ /* Don't issue the callback if TSC accesses are not emulated */
+ if (hv_reenlightenment_cb && emu_status.inprogress)
+ hv_reenlightenment_cb();
+}
+static DECLARE_DELAYED_WORK(hv_reenlightenment_work, hv_reenlightenment_notify);
+
+void hyperv_stop_tsc_emulation(void)
+{
+ u64 freq;
+ struct hv_tsc_emulation_status emu_status;
+
+ rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);
+ emu_status.inprogress = 0;
+ wrmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);
+
+ rdmsrl(HV_X64_MSR_TSC_FREQUENCY, freq);
+ tsc_khz = div64_u64(freq, 1000);
+}
+EXPORT_SYMBOL_GPL(hyperv_stop_tsc_emulation);
+
+static inline bool hv_reenlightenment_available(void)
+{
+ /*
+ * Check for required features and priviliges to make TSC frequency
+ * change notifications work.
+ */
+ return ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS &&
+ ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE &&
+ ms_hyperv.features & HV_X64_ACCESS_REENLIGHTENMENT;
+}
+
+__visible void __irq_entry hyperv_reenlightenment_intr(struct pt_regs *regs)
+{
+ entering_ack_irq();
+
+ schedule_delayed_work(&hv_reenlightenment_work, HZ/10);
+
+ exiting_irq();
+}
+
+void set_hv_tscchange_cb(void (*cb)(void))
+{
+ struct hv_reenlightenment_control re_ctrl = {
+ .vector = HYPERV_REENLIGHTENMENT_VECTOR,
+ .enabled = 1,
+ .target_vp = hv_vp_index[smp_processor_id()]
+ };
+ struct hv_tsc_emulation_control emu_ctrl = {.enabled = 1};
+
+ if (!hv_reenlightenment_available()) {
+ pr_warn("Hyper-V: reenlightenment support is unavailable\n");
+ return;
+ }
+
+ hv_reenlightenment_cb = cb;
+
+ /* Make sure callback is registered before we write to MSRs */
+ wmb();
+
+ wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
+ wrmsrl(HV_X64_MSR_TSC_EMULATION_CONTROL, *((u64 *)&emu_ctrl));
+}
+EXPORT_SYMBOL_GPL(set_hv_tscchange_cb);
+
+void clear_hv_tscchange_cb(void)
+{
+ struct hv_reenlightenment_control re_ctrl;
+
+ if (!hv_reenlightenment_available())
+ return;
+
+ rdmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *(u64 *)&re_ctrl);
+ re_ctrl.enabled = 0;
+ wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *(u64 *)&re_ctrl);
+
+ hv_reenlightenment_cb = NULL;
+}
+EXPORT_SYMBOL_GPL(clear_hv_tscchange_cb);
+
/*
* This function is to be invoked early in the boot sequence after the
* hypervisor has been detected.