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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [RFC PATCH 25/26] x86/kvm: Guest support for dynamic hints
If the hypervisor supports KVM_FEATURE_DYNAMIC_HINTS, then register a
callback vector (currently chosen to be HYPERVISOR_CALLBACK_VECTOR.)
The callback triggers on a change in the active hints which are
are exported via KVM CPUID in %ecx.
Trigger re-evaluation of KVM_HINTS based on change in their active
status.
Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
---
arch/x86/Kconfig | 1 +
arch/x86/entry/entry_64.S | 5 +++
arch/x86/include/asm/kvm_para.h | 7 ++++
arch/x86/kernel/kvm.c | 58 ++++++++++++++++++++++++++++++---
include/asm-generic/kvm_para.h | 4 +++
include/linux/kvm_para.h | 5 +++
6 files changed, 76 insertions(+), 4 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e0629558b6b5..23b239d184fc 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -810,6 +810,7 @@ config KVM_GUEST
select PARAVIRT_CLOCK
select ARCH_CPUIDLE_HALTPOLL
select PARAVIRT_RUNTIME
+ select X86_HV_CALLBACK_VECTOR
default y
---help---
This option enables various optimizations for running under the KVM
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 0e9504fabe52..96b2a243c54f 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1190,6 +1190,11 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
acrn_hv_callback_vector acrn_hv_vector_handler
#endif
+#if IS_ENABLED(CONFIG_KVM_GUEST)
+apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
+ kvm_callback_vector kvm_do_callback
+#endif
+
idtentry debug do_debug has_error_code=0
paranoid=1 shift_ist=IST_INDEX_DB ist_offset=DB_STACK_OFFSET
idtentry int3 do_int3 has_error_code=0
create_gap=1
idtentry stack_segment do_stack_segment has_error_code=1
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 9b4df6eaa11a..5a7ca5639c2e 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -88,11 +88,13 @@ static inline long kvm_hypercall4(unsigned int nr, unsigned
long p1,
bool kvm_para_available(void);
unsigned int kvm_arch_para_features(void);
unsigned int kvm_arch_para_hints(void);
+unsigned int kvm_arch_para_active_hints(void);
void kvm_async_pf_task_wait(u32 token, int interrupt_kernel);
void kvm_async_pf_task_wake(u32 token);
u32 kvm_read_and_reset_pf_reason(void);
extern void kvm_disable_steal_time(void);
void do_async_page_fault(struct pt_regs *regs, unsigned long error_code,
unsigned long address);
+void kvm_callback_vector(struct pt_regs *regs);
#ifdef CONFIG_PARAVIRT_SPINLOCKS
void __init kvm_spinlock_init(void);
@@ -121,6 +123,11 @@ static inline unsigned int kvm_arch_para_hints(void)
return 0;
}
+static inline unsigned int kvm_arch_para_active_hints(void)
+{
+ return 0;
+}
+
static inline u32 kvm_read_and_reset_pf_reason(void)
{
return 0;
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 1cb7eab805a6..163b7a7ec5f9 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -25,6 +25,8 @@
#include <linux/nmi.h>
#include <linux/swait.h>
#include <linux/memory.h>
+#include <linux/irq.h>
+#include <linux/interrupt.h>
#include <asm/timer.h>
#include <asm/cpu.h>
#include <asm/traps.h>
@@ -438,7 +440,7 @@ static void __init sev_map_percpu_data(void)
static bool pv_tlb_flush_supported(void)
{
return (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
- !kvm_para_has_hint(KVM_HINTS_REALTIME) &&
+ !kvm_para_has_active_hint(KVM_HINTS_REALTIME) &&
kvm_para_has_feature(KVM_FEATURE_STEAL_TIME));
}
@@ -463,7 +465,7 @@ static bool pv_ipi_supported(void)
static bool pv_sched_yield_supported(void)
{
return (kvm_para_has_feature(KVM_FEATURE_PV_SCHED_YIELD) &&
- !kvm_para_has_hint(KVM_HINTS_REALTIME) &&
+ !kvm_para_has_active_hint(KVM_HINTS_REALTIME) &&
kvm_para_has_feature(KVM_FEATURE_STEAL_TIME));
}
@@ -568,7 +570,7 @@ static void kvm_smp_send_call_func_ipi(const struct cpumask
*mask)
static void __init kvm_smp_prepare_cpus(unsigned int max_cpus)
{
native_smp_prepare_cpus(max_cpus);
- if (kvm_para_has_hint(KVM_HINTS_REALTIME))
+ if (kvm_para_has_active_hint(KVM_HINTS_REALTIME))
static_branch_disable(&virt_spin_lock_key);
}
@@ -654,6 +656,13 @@ static bool kvm_pv_tlb(void)
return cond;
}
+#ifdef CONFIG_PARAVIRT_RUNTIME
+static bool has_dynamic_hint;
+static void __init kvm_register_callback_vector(void);
+#else
+#define has_dynamic_hint false
+#endif /* CONFIG_PARAVIRT_RUNTIME */
+
static void __init kvm_guest_init(void)
{
int i;
@@ -674,6 +683,12 @@ 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 (IS_ENABLED(CONFIG_PARAVIRT_RUNTIME) &&
+ kvm_para_has_feature(KVM_FEATURE_DYNAMIC_HINTS)) {
+ kvm_register_callback_vector();
+ has_dynamic_hint = true;
+ }
+
#ifdef CONFIG_SMP
smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus;
smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
@@ -729,12 +744,27 @@ unsigned int kvm_arch_para_features(void)
return cpuid_eax(kvm_cpuid_base() | KVM_CPUID_FEATURES);
}
+/*
+ * Universe of hints that's ever been given to this guest.
+ */
unsigned int kvm_arch_para_hints(void)
{
return cpuid_edx(kvm_cpuid_base() | KVM_CPUID_FEATURES);
}
EXPORT_SYMBOL_GPL(kvm_arch_para_hints);
+/*
+ * Currently active set of hints. Reading can race with modifications.
+ */
+unsigned int kvm_arch_para_active_hints(void)
+{
+ if (has_dynamic_hint)
+ return cpuid_ecx(kvm_cpuid_base() | KVM_CPUID_FEATURES);
+ else
+ return kvm_arch_para_hints();
+}
+EXPORT_SYMBOL_GPL(kvm_arch_para_active_hints);
+
static uint32_t __init kvm_detect(void)
{
return kvm_cpuid_base();
@@ -878,7 +908,7 @@ static inline bool kvm_para_lock_ops(void)
{
/* Does host kernel support KVM_FEATURE_PV_UNHALT? */
return kvm_para_has_feature(KVM_FEATURE_PV_UNHALT) &&
- !kvm_para_has_hint(KVM_HINTS_REALTIME);
+ !kvm_para_has_active_hint(KVM_HINTS_REALTIME);
}
static bool kvm_pv_spinlock(void)
@@ -975,4 +1005,24 @@ void kvm_trigger_reprobe_cpuid(struct work_struct *work)
mutex_unlock(&text_mutex);
}
+
+static DECLARE_WORK(trigger_reprobe, kvm_trigger_reprobe_cpuid);
+
+void __irq_entry kvm_do_callback(struct pt_regs *regs)
+{
+ struct pt_regs *old_regs = set_irq_regs(regs);
+
+ irq_enter();
+ inc_irq_stat(irq_hv_callback_count);
+
+ schedule_work(&trigger_reprobe);
+ irq_exit();
+ set_irq_regs(old_regs);
+}
+
+static void __init kvm_register_callback_vector(void)
+{
+ alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, kvm_callback_vector);
+ wrmsrl(MSR_KVM_HINT_VECTOR, HYPERVISOR_CALLBACK_VECTOR);
+}
#endif /* CONFIG_PARAVIRT_RUNTIME */
diff --git a/include/asm-generic/kvm_para.h b/include/asm-generic/kvm_para.h
index 728e5c5706c4..4a575299ad62 100644
--- a/include/asm-generic/kvm_para.h
+++ b/include/asm-generic/kvm_para.h
@@ -24,6 +24,10 @@ static inline unsigned int kvm_arch_para_hints(void)
return 0;
}
+static inline unsigned int kvm_arch_para_active_hints(void)
+{
+ return 0;
+}
static inline bool kvm_para_available(void)
{
return false;
diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h
index f23b90b02898..c98d3944d25a 100644
--- a/include/linux/kvm_para.h
+++ b/include/linux/kvm_para.h
@@ -14,4 +14,9 @@ static inline bool kvm_para_has_hint(unsigned int feature)
{
return !!(kvm_arch_para_hints() & (1UL << feature));
}
+
+static inline bool kvm_para_has_active_hint(unsigned int feature)
+{
+ return !!(kvm_arch_para_active_hints() & BIT(feature));
+}
#endif /* __LINUX_KVM_PARA_H */
--
2.20.1
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