[PATCH v2 4/9] KVM: mark requests that do not need a wakeup

Radim Krčmář
2017-04-26T20:32:22Z

Some operations must ensure that the guest is not running with stale
data, but if the guest is halted, then the update can wait until another
event happens. kvm_make_all_requests() currently doesn't wake up, so we
can mark all requests used with it.

First 8 bits were arbitrarily reserved for request numbers.

Most uses of requests have the request type as a constant, so a compiler
will optimize the '&'.

An alternative would be to have an inline function that would return
whether the request needs a wake-up or not, but I like this one better
even though it might produce worse assembly.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
v2: use GENMASK [Marc]
---
arch/arm/include/asm/kvm_host.h | 2 +-
arch/arm64/include/asm/kvm_host.h | 2 +-
arch/x86/include/asm/kvm_host.h | 6 +++---
include/linux/kvm_host.h | 12 +++++++-----
4 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index de67ce647501..49358f20d36f 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -44,7 +44,7 @@
#define KVM_MAX_VCPUS VGIC_V2_MAX_CPUS
#endif

-#define KVM_REQ_VCPU_EXIT 8
+#define KVM_REQ_VCPU_EXIT (8 | KVM_REQUEST_NO_WAKEUP)

u32 *kvm_vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num, u32 mode);
int __attribute_const__ kvm_target_cpu(void);
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 522e4f60976e..1c9458a7ec92 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -41,7 +41,7 @@

#define KVM_VCPU_MAX_FEATURES 4

-#define KVM_REQ_VCPU_EXIT 8
+#define KVM_REQ_VCPU_EXIT (8 | KVM_REQUEST_NO_WAKEUP)

int __attribute_const__ kvm_target_cpu(void);
int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f5c942edbc86..19219826bed6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -61,10 +61,10 @@
#define KVM_REQ_PMI 19
#define KVM_REQ_SMI 20
#define KVM_REQ_MASTERCLOCK_UPDATE 21
-#define KVM_REQ_MCLOCK_INPROGRESS 22
-#define KVM_REQ_SCAN_IOAPIC 23
+#define KVM_REQ_MCLOCK_INPROGRESS (22 | KVM_REQUEST_NO_WAKEUP)
+#define KVM_REQ_SCAN_IOAPIC (23 | KVM_REQUEST_NO_WAKEUP)
#define KVM_REQ_GLOBAL_CLOCK_UPDATE 24
-#define KVM_REQ_APIC_PAGE_RELOAD 25
+#define KVM_REQ_APIC_PAGE_RELOAD (25 | KVM_REQUEST_NO_WAKEUP)
#define KVM_REQ_HV_CRASH 26
#define KVM_REQ_IOAPIC_EOI_EXIT 27
#define KVM_REQ_HV_RESET 28
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 374fa92c7657..a805ddcb7eb0 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -115,12 +115,14 @@ static inline bool is_error_page(struct page *page)
return IS_ERR(page);
}

+#define KVM_REQUEST_MASK GENMASK(7,0)
+#define KVM_REQUEST_NO_WAKEUP BIT(8)
/*
* Architecture-independent vcpu->requests bit members
* Bits 4-7 are reserved for more arch-independent bits.
*/
-#define KVM_REQ_TLB_FLUSH 0
-#define KVM_REQ_MMU_RELOAD 1
+#define KVM_REQ_TLB_FLUSH (0 | KVM_REQUEST_NO_WAKEUP)
+#define KVM_REQ_MMU_RELOAD (1 | KVM_REQUEST_NO_WAKEUP)
#define KVM_REQ_PENDING_TIMER 2
#define KVM_REQ_UNHALT 3

@@ -1076,17 +1078,17 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu)
* caller. Paired with the smp_mb__after_atomic in kvm_check_request.
*/
smp_wmb();
- set_bit(req, &vcpu->requests);
+ set_bit(req & KVM_REQUEST_MASK, &vcpu->requests);
}

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

static inline void kvm_clear_request(int req, struct kvm_vcpu *vcpu)
{
- clear_bit(req, &vcpu->requests);
+ clear_bit(req & KVM_REQUEST_MASK, &vcpu->requests);
}

static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
--
2.12.2