[PATCH v2 5/9] KVM: remove KVM_REQ_UNHALT

Paolo Bonzini
2022-08-11T21:06:50Z

KVM_REQ_UNHALT is now unnecessary because it is replaced by the return
value of kvm_vcpu_block/kvm_vcpu_halt. Remove it.

No functional change intended.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
Documentation/virt/kvm/vcpu-requests.rst | 28 +-----------------------
arch/arm64/kvm/arm.c | 1 -
arch/mips/kvm/emulate.c | 1 -
arch/powerpc/kvm/book3s_pr.c | 1 -
arch/powerpc/kvm/book3s_pr_papr.c | 1 -
arch/powerpc/kvm/booke.c | 1 -
arch/powerpc/kvm/powerpc.c | 1 -
arch/riscv/kvm/vcpu_insn.c | 1 -
arch/s390/kvm/kvm-s390.c | 2 --
arch/x86/kvm/x86.c | 2 --
arch/x86/kvm/xen.c | 1 -
include/linux/kvm_host.h | 3 +--
virt/kvm/kvm_main.c | 5 -----
13 files changed, 2 insertions(+), 46 deletions(-)

diff --git a/Documentation/virt/kvm/vcpu-requests.rst b/Documentation/virt/kvm/vcpu-requests.rst
index 31f62b64e07b..87f04c1fa53d 100644
--- a/Documentation/virt/kvm/vcpu-requests.rst
+++ b/Documentation/virt/kvm/vcpu-requests.rst
@@ -97,7 +97,7 @@ VCPU requests are simply bit indices of the ``vcpu->requests`` bitmap.
This means general bitops, like those documented in [atomic-ops]_ could
also be used, e.g. ::

- clear_bit(KVM_REQ_UNHALT & KVM_REQUEST_MASK, &vcpu->requests);
+ clear_bit(KVM_REQ_UNBLOCK & KVM_REQUEST_MASK, &vcpu->requests);

However, VCPU request users should refrain from doing so, as it would
break the abstraction. The first 8 bits are reserved for architecture
@@ -126,17 +126,6 @@ KVM_REQ_UNBLOCK
or in order to update the interrupt routing and ensure that assigned
devices will wake up the vCPU.

-KVM_REQ_UNHALT
-
- This request may be made from the KVM common function kvm_vcpu_block(),
- which is used to emulate an instruction that causes a CPU to halt until
- one of an architectural specific set of events and/or interrupts is
- received (determined by checking kvm_arch_vcpu_runnable()). When that
- event or interrupt arrives kvm_vcpu_block() makes the request. This is
- in contrast to when kvm_vcpu_block() returns due to any other reason,
- such as a pending signal, which does not indicate the VCPU's halt
- emulation should stop, and therefore does not make the request.
-
KVM_REQ_OUTSIDE_GUEST_MODE

This "request" ensures the target vCPU has exited guest mode prior to the
@@ -297,21 +286,6 @@ architecture dependent. kvm_vcpu_block() calls kvm_arch_vcpu_runnable()
to check if it should awaken. One reason to do so is to provide
architectures a function where requests may be checked if necessary.

-Clearing Requests
------------------
-
-Generally it only makes sense for the receiving VCPU thread to clear a
-request. However, in some circumstances, such as when the requesting
-thread and the receiving VCPU thread are executed serially, such as when
-they are the same thread, or when they are using some form of concurrency
-control to temporarily execute synchronously, then it's possible to know
-that the request may be cleared immediately, rather than waiting for the
-receiving VCPU thread to handle the request in VCPU RUN. The only current
-examples of this are kvm_vcpu_block() calls made by VCPUs to block
-themselves. A possible side-effect of that call is to make the
-KVM_REQ_UNHALT request, which may then be cleared immediately when the
-VCPU returns from the call.
-
References
==========

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 986cee6fbc7f..0bbd1ce601a5 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -666,7 +666,6 @@ void kvm_vcpu_wfi(struct kvm_vcpu *vcpu)

kvm_vcpu_halt(vcpu);
vcpu_clear_flag(vcpu, IN_WFIT);
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);

preempt_disable();
vgic_v4_load(vcpu);
diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index 77d760d45c48..c11143586765 100644
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -959,7 +959,6 @@ enum emulation_result kvm_mips_emul_wait(struct kvm_vcpu *vcpu)
* We we are runnable, then definitely go off to user space to
* check if any I/O interrupts are pending.
*/
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
if (r > 0)
vcpu->run->exit_reason = KVM_EXIT_IRQ_WINDOW_OPEN;
}
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index d6abed6e51e6..9fc4dd8f66eb 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -499,7 +499,6 @@ static void kvmppc_set_msr_pr(struct kvm_vcpu *vcpu, u64 msr)
if (msr & MSR_POW) {
if (!vcpu->arch.pending_exceptions) {
kvm_vcpu_halt(vcpu);
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
vcpu->stat.generic.halt_wakeup++;

/* Unset POW bit after we woke up */
diff --git a/arch/powerpc/kvm/book3s_pr_papr.c b/arch/powerpc/kvm/book3s_pr_papr.c
index a1f2978b2a86..b2c89e850d7a 100644
--- a/arch/powerpc/kvm/book3s_pr_papr.c
+++ b/arch/powerpc/kvm/book3s_pr_papr.c
@@ -393,7 +393,6 @@ int kvmppc_h_pr(struct kvm_vcpu *vcpu, unsigned long cmd)
case H_CEDE:
kvmppc_set_msr_fast(vcpu, kvmppc_get_msr(vcpu) | MSR_EE);
kvm_vcpu_halt(vcpu);
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
vcpu->stat.generic.halt_wakeup++;
return EMULATE_DONE;
case H_LOGICAL_CI_LOAD:
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 06c5830a93f9..7b4920e9fd26 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -719,7 +719,6 @@ int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu)
if (vcpu->arch.shared->msr & MSR_WE) {
local_irq_enable();
kvm_vcpu_halt(vcpu);
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
hard_irq_disable();

kvmppc_set_exit_type(vcpu, EMULATED_MTMSRWE_EXITS);
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 191992fcb2c2..3c384ed1d9fc 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -238,7 +238,6 @@ int kvmppc_kvm_pv(struct kvm_vcpu *vcpu)
case EV_HCALL_TOKEN(EV_IDLE):
r = EV_SUCCESS;
kvm_vcpu_halt(vcpu);
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
break;
default:
r = EV_UNIMPLEMENTED;
diff --git a/arch/riscv/kvm/vcpu_insn.c b/arch/riscv/kvm/vcpu_insn.c
index 7eb90a47b571..0bb52761a3f7 100644
--- a/arch/riscv/kvm/vcpu_insn.c
+++ b/arch/riscv/kvm/vcpu_insn.c
@@ -191,7 +191,6 @@ void kvm_riscv_vcpu_wfi(struct kvm_vcpu *vcpu)
kvm_vcpu_srcu_read_unlock(vcpu);
kvm_vcpu_halt(vcpu);
kvm_vcpu_srcu_read_lock(vcpu);
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
}
}

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index edfd4bbd0cba..aa39ea4582bd 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4343,8 +4343,6 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
goto retry;
}

- /* nothing to do, just clear the request */
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
/* we left the vsie handler, nothing to do, just clear the request */
kvm_clear_request(KVM_REQ_VSIE_RESTART, vcpu);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 416df0fc7fda..7f084613fac8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10635,7 +10635,6 @@ static inline int vcpu_block(struct kvm_vcpu *vcpu)
if (hv_timer)
kvm_lapic_switch_to_hv_timer(vcpu);

- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
if (r <= 0)
return 1;
}
@@ -10842,7 +10841,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
r = 0;
goto out;
}
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
r = -EAGAIN;
if (signal_pending(current)) {
r = -EINTR;
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 280cb5dc7341..93c628d3e3a9 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1065,7 +1065,6 @@ static bool kvm_xen_schedop_poll(struct kvm_vcpu *vcpu, bool longmode,
del_timer(&vcpu->arch.xen.poll_timer);

vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
- kvm_clear_request(KVM_REQ_UNHALT, vcpu);
}

vcpu->arch.xen.poll_evtchn = 0;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index cbd9577e5447..cfe46830783f 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -151,12 +151,11 @@ static inline bool is_error_page(struct page *page)
#define KVM_REQUEST_NO_ACTION BIT(10)
/*
* Architecture-independent vcpu->requests bit members
- * Bits 4-7 are reserved for more arch-independent bits.
+ * Bits 3-7 are reserved for more arch-independent bits.
*/
#define KVM_REQ_TLB_FLUSH (0 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
#define KVM_REQ_VM_DEAD (1 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
#define KVM_REQ_UNBLOCK 2
-#define KVM_REQ_UNHALT 3
#define KVM_REQUEST_ARCH_BASE 8

/*
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e827805b7b28..18292f028536 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3414,7 +3414,6 @@ static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
int idx = srcu_read_lock(&vcpu->kvm->srcu);

if (kvm_arch_vcpu_runnable(vcpu)) {
- kvm_make_request(KVM_REQ_UNHALT, vcpu);
ret = 1;
goto out;
}
@@ -3508,10 +3507,6 @@ int kvm_vcpu_halt(struct kvm_vcpu *vcpu)
stop = do_halt_poll ? start : ktime_add_ns(start, vcpu->halt_poll_ns);

do {
- /*
- * This sets KVM_REQ_UNHALT if an interrupt
- * arrives.
- */
r = kvm_vcpu_check_block(vcpu);
if (r != 0)
goto out;
--
2.31.1