[PATCH v3 01/10] KVM: add kvm_request_pending

Andrew Jones
2017-05-03T16:06:26Z

From: Radim Krčmář <rkrcmar@redhat.com>

A first step in vcpu->requests encapsulation. Additionally, we now
use READ_ONCE() when accessing vcpu->requests, which ensures we
always load vcpu->requests when it's accessed. This is important as
other threads can change it any time. Also, READ_ONCE() documents
that vcpu->requests is used with other threads, likely requiring
memory barriers, which it does.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
[ Documented the new use of READ_ONCE(). ]
Signed-off-by: Andrew Jones <drjones@redhat.com>
---
arch/mips/kvm/trap_emul.c | 2 +-
arch/powerpc/kvm/booke.c | 2 +-
arch/powerpc/kvm/powerpc.c | 5 ++---
arch/s390/kvm/kvm-s390.c | 2 +-
arch/x86/kvm/x86.c | 4 ++--
include/linux/kvm_host.h | 5 +++++
6 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c
index b1fa53b252ea..9ac8b1d62643 100644
--- a/arch/mips/kvm/trap_emul.c
+++ b/arch/mips/kvm/trap_emul.c
@@ -1029,7 +1029,7 @@ static void kvm_trap_emul_check_requests(struct kvm_vcpu *vcpu, int cpu,
struct mm_struct *mm;
int i;

- if (likely(!vcpu->requests))
+ if (likely(!kvm_request_pending(vcpu)))
return;

if (kvm_check_request(KVM_REQ_TLB_FLUSH, vcpu)) {
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index ab968f60d14c..c427202b3cbb 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -682,7 +682,7 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)

kvmppc_core_check_exceptions(vcpu);

- if (vcpu->requests) {
+ if (kvm_request_pending(vcpu)) {
/* Exception delivery raised request; start over */
return 1;
}
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 378ed9cee1f9..0ce1a219984e 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -52,8 +52,7 @@ EXPORT_SYMBOL_GPL(kvmppc_pr_ops);

int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
{
- return !!(v->arch.pending_exceptions) ||
- v->requests;
+ return !!(v->arch.pending_exceptions) || kvm_request_pending(v);
}

int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
@@ -105,7 +104,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
*/
smp_mb();

- if (vcpu->requests) {
+ if (kvm_request_pending(vcpu)) {
/* Make sure we process requests preemptable */
local_irq_enable();
trace_kvm_check_requests(vcpu);
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 9ab89f73612a..66c33eb53707 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2396,7 +2396,7 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
{
retry:
kvm_s390_vcpu_request_handled(vcpu);
- if (!vcpu->requests)
+ if (!kvm_request_pending(vcpu))
return 0;
/*
* We use MMU_RELOAD just to re-arm the ipte notifier for the
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 073175e14083..92e643af848e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6720,7 +6720,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)

bool req_immediate_exit = false;

- if (vcpu->requests) {
+ if (kvm_request_pending(vcpu)) {
if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu))
kvm_mmu_unload(vcpu);
if (kvm_check_request(KVM_REQ_MIGRATE_TIMER, vcpu))
@@ -6884,7 +6884,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
kvm_x86_ops->sync_pir_to_irr(vcpu);
}

- if (vcpu->mode == EXITING_GUEST_MODE || vcpu->requests
+ if (vcpu->mode == EXITING_GUEST_MODE || kvm_request_pending(vcpu)
|| need_resched() || signal_pending(current)) {
vcpu->mode = OUTSIDE_GUEST_MODE;
smp_wmb();
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 94b12154e67c..b1f7d40a4ca4 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1111,6 +1111,11 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu)
set_bit(req & KVM_REQUEST_MASK, &vcpu->requests);
}

+static inline bool kvm_request_pending(struct kvm_vcpu *vcpu)
+{
+ return READ_ONCE(vcpu->requests);
+}
+
static inline bool kvm_test_request(int req, struct kvm_vcpu *vcpu)
{
return test_bit(req & KVM_REQUEST_MASK, &vcpu->requests);
--
2.9.3

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu