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Message-Id: <20200408050323.4237-23-ankur.a.arora@oracle.com>
Date: Tue, 7 Apr 2020 22:03:19 -0700
From: Ankur Arora <ankur.a.arora@...cle.com>
To: linux-kernel@...r.kernel.org, x86@...nel.org
Cc: peterz@...radead.org, hpa@...or.com, jpoimboe@...hat.com,
namit@...are.com, mhiramat@...nel.org, jgross@...e.com,
bp@...en8.de, vkuznets@...hat.com, pbonzini@...hat.com,
boris.ostrovsky@...cle.com, mihai.carabas@...cle.com,
kvm@...r.kernel.org, xen-devel@...ts.xenproject.org,
virtualization@...ts.linux-foundation.org,
Ankur Arora <ankur.a.arora@...cle.com>
Subject: [RFC PATCH 22/26] kvm/paravirt: Encapsulate KVM pv switching logic
KVM pv-ops are dependent on KVM features/hints which are exposed
via CPUID. Decouple the probing and the enabling of these ops from
__init so they can be called post-init as well.
Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
arch/x86/Kconfig | 1 +
arch/x86/kernel/kvm.c | 87 ++++++++++++++++++++++++++++++-------------
2 files changed, 63 insertions(+), 25 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 605619938f08..e0629558b6b5 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -809,6 +809,7 @@ config KVM_GUEST
depends on PARAVIRT
select PARAVIRT_CLOCK
select ARCH_CPUIDLE_HALTPOLL
+ select PARAVIRT_RUNTIME
default y
---help---
This option enables various optimizations for running under the KVM
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index e56d263159d7..31f5ecfd3907 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -24,6 +24,7 @@
#include <linux/debugfs.h>
#include <linux/nmi.h>
#include <linux/swait.h>
+#include <linux/memory.h>
#include <asm/timer.h>
#include <asm/cpu.h>
#include <asm/traps.h>
@@ -262,12 +263,20 @@ do_async_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned lon
}
NOKPROBE_SYMBOL(do_async_page_fault);
+static bool kvm_pv_io_delay(void)
+{
+ bool cond = kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY);
+
+ paravirt_stage_alt(cond, cpu.io_delay, kvm_io_delay);
+
+ return cond;
+}
+
static void __init paravirt_ops_setup(void)
{
pv_info.name = "KVM";
- if (kvm_para_has_feature(KVM_FEATURE_NOP_IO_DELAY))
- pv_ops.cpu.io_delay = kvm_io_delay;
+ kvm_pv_io_delay();
#ifdef CONFIG_X86_IO_APIC
no_timer_check = 1;
@@ -432,6 +441,15 @@ static bool pv_tlb_flush_supported(void)
kvm_para_has_feature(KVM_FEATURE_STEAL_TIME));
}
+static bool kvm_pv_steal_clock(void)
+{
+ bool cond = kvm_para_has_feature(KVM_FEATURE_STEAL_TIME);
+
+ paravirt_stage_alt(cond, time.steal_clock, kvm_steal_clock);
+
+ return cond;
+}
+
static DEFINE_PER_CPU(cpumask_var_t, __pv_cpu_mask);
#ifdef CONFIG_SMP
@@ -624,6 +642,17 @@ static void kvm_flush_tlb_others(const struct cpumask *cpumask,
native_flush_tlb_others(flushmask, info);
}
+static bool kvm_pv_tlb(void)
+{
+ bool cond = pv_tlb_flush_supported();
+
+ paravirt_stage_alt(cond, mmu.flush_tlb_others,
+ kvm_flush_tlb_others);
+ paravirt_stage_alt(cond, mmu.tlb_remove_table,
+ tlb_remove_table);
+ return cond;
+}
+
static void __init kvm_guest_init(void)
{
int i;
@@ -635,16 +664,11 @@ static void __init kvm_guest_init(void)
if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF))
x86_init.irqs.trap_init = kvm_apf_trap_init;
- if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
+ if (kvm_pv_steal_clock())
has_steal_clock = 1;
- pv_ops.time.steal_clock = kvm_steal_clock;
- }
- if (pv_tlb_flush_supported()) {
- pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
- pv_ops.mmu.tlb_remove_table = tlb_remove_table;
+ if (kvm_pv_tlb())
pr_info("KVM setup pv remote TLB flush\n");
- }
if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
apic_set_eoi_write(kvm_guest_apic_eoi_write);
@@ -849,33 +873,46 @@ asm(
#endif
+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);
+}
+
+static bool kvm_pv_spinlock(void)
+{
+ bool cond = kvm_para_lock_ops();
+ bool preempt_cond = cond &&
+ kvm_para_has_feature(KVM_FEATURE_STEAL_TIME);
+
+ paravirt_stage_alt(cond, lock.queued_spin_lock_slowpath,
+ __pv_queued_spin_lock_slowpath);
+ paravirt_stage_alt(cond, lock.queued_spin_unlock.func,
+ PV_CALLEE_SAVE(__pv_queued_spin_unlock).func);
+ paravirt_stage_alt(cond, lock.wait, kvm_wait);
+ paravirt_stage_alt(cond, lock.kick, kvm_kick_cpu);
+
+ paravirt_stage_alt(preempt_cond,
+ lock.vcpu_is_preempted.func,
+ PV_CALLEE_SAVE(__kvm_vcpu_is_preempted).func);
+ return cond;
+}
+
/*
* Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present.
*/
void __init kvm_spinlock_init(void)
{
- /* Does host kernel support KVM_FEATURE_PV_UNHALT? */
- if (!kvm_para_has_feature(KVM_FEATURE_PV_UNHALT))
- return;
-
- if (kvm_para_has_hint(KVM_HINTS_REALTIME))
- return;
/* Don't use the pvqspinlock code if there is only 1 vCPU. */
if (num_possible_cpus() == 1)
return;
- __pv_init_lock_hash();
- pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
- pv_ops.lock.queued_spin_unlock =
- PV_CALLEE_SAVE(__pv_queued_spin_unlock);
- pv_ops.lock.wait = kvm_wait;
- pv_ops.lock.kick = kvm_kick_cpu;
+ if (!kvm_pv_spinlock())
+ return;
- if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) {
- pv_ops.lock.vcpu_is_preempted =
- PV_CALLEE_SAVE(__kvm_vcpu_is_preempted);
- }
+ __pv_init_lock_hash();
}
#endif /* CONFIG_PARAVIRT_SPINLOCKS */
--
2.20.1
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