[PATCH v2 4/7] entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper

[Sean Christopherson <seanjc@google.com>]

Move KVM's morphing of pending signals into userspace exits into KVM
proper, and drop the @vcpu param from xfer_to_guest_mode_handle_work().
How KVM responds to -EINTR is a detail that really belongs in KVM itself,
and invoking kvm_handle_signal_exit() from kernel code creates an inverted
module dependency.  E.g. attempting to move kvm_handle_signal_exit() into
kvm_main.c would generate an linker error when building kvm.ko as a module.

Dropping KVM details will also converting the KVM "entry" code into a more
generic virtualization framework so that it can be used when running as a
Hyper-V root partition.

Lastly, eliminating usage of "struct kvm_vcpu" outside of KVM is also nice
to have for KVM x86 developers, as keeping the details of kvm_vcpu purely
within KVM allows changing the layout of the structure without having to
boot into a new kernel, e.g. allows rebuilding and reloading kvm.ko with a
modified kvm_vcpu structure as part of debug/development.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/arm64/kvm/arm.c      |  3 +--
 arch/loongarch/kvm/vcpu.c |  3 +--
 arch/riscv/kvm/vcpu.c     |  3 +--
 arch/x86/kvm/vmx/vmx.c    |  1 -
 arch/x86/kvm/x86.c        |  3 +--
 include/linux/entry-kvm.h | 11 +++--------
 include/linux/kvm_host.h  | 13 ++++++++++++-
 kernel/entry/kvm.c        | 13 +++++--------
 8 files changed, 24 insertions(+), 26 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 888f7c7abf54..418fd3043467 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -6,7 +6,6 @@
 
 #include <linux/bug.h>
 #include <linux/cpu_pm.h>
-#include <linux/entry-kvm.h>
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/kvm_host.h>
@@ -1177,7 +1176,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 		/*
 		 * Check conditions before entering the guest
 		 */
-		ret = xfer_to_guest_mode_handle_work(vcpu);
+		ret = kvm_xfer_to_guest_mode_handle_work(vcpu);
 		if (!ret)
 			ret = 1;
 
diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
index d1b8c50941ca..514256b25ba1 100644
--- a/arch/loongarch/kvm/vcpu.c
+++ b/arch/loongarch/kvm/vcpu.c
@@ -4,7 +4,6 @@
  */
 
 #include <linux/kvm_host.h>
-#include <linux/entry-kvm.h>
 #include <asm/fpu.h>
 #include <asm/lbt.h>
 #include <asm/loongarch.h>
@@ -251,7 +250,7 @@ static int kvm_enter_guest_check(struct kvm_vcpu *vcpu)
 	/*
 	 * Check conditions before entering the guest
 	 */
-	ret = xfer_to_guest_mode_handle_work(vcpu);
+	ret = kvm_xfer_to_guest_mode_handle_work(vcpu);
 	if (ret < 0)
 		return ret;
 
diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index f001e56403f9..251e787f2ebc 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -7,7 +7,6 @@
  */
 
 #include <linux/bitops.h>
-#include <linux/entry-kvm.h>
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/kdebug.h>
@@ -910,7 +909,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 	run->exit_reason = KVM_EXIT_UNKNOWN;
 	while (ret > 0) {
 		/* Check conditions before entering the guest */
-		ret = xfer_to_guest_mode_handle_work(vcpu);
+		ret = kvm_xfer_to_guest_mode_handle_work(vcpu);
 		if (ret)
 			continue;
 		ret = 1;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index aa157fe5b7b3..d7c86613e50a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -28,7 +28,6 @@
 #include <linux/slab.h>
 #include <linux/tboot.h>
 #include <linux/trace_events.h>
-#include <linux/entry-kvm.h>
 
 #include <asm/apic.h>
 #include <asm/asm.h>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a1c49bc681c4..0b13b8bf69e5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -59,7 +59,6 @@
 #include <linux/sched/stat.h>
 #include <linux/sched/isolation.h>
 #include <linux/mem_encrypt.h>
-#include <linux/entry-kvm.h>
 #include <linux/suspend.h>
 #include <linux/smp.h>
 
@@ -11241,7 +11240,7 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
 
 		if (__xfer_to_guest_mode_work_pending()) {
 			kvm_vcpu_srcu_read_unlock(vcpu);
-			r = xfer_to_guest_mode_handle_work(vcpu);
+			r = kvm_xfer_to_guest_mode_handle_work(vcpu);
 			kvm_vcpu_srcu_read_lock(vcpu);
 			if (r)
 				return r;
diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
index 16149f6625e4..3644de7e6019 100644
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-kvm.h
@@ -21,8 +21,6 @@
 	 _TIF_NOTIFY_SIGNAL | _TIF_NOTIFY_RESUME |			\
 	 ARCH_XFER_TO_GUEST_MODE_WORK)
 
-struct kvm_vcpu;
-
 /**
  * arch_xfer_to_guest_mode_handle_work - Architecture specific xfer to guest
  *					 mode work handling function.
@@ -32,12 +30,10 @@ struct kvm_vcpu;
  * Invoked from xfer_to_guest_mode_handle_work(). Defaults to NOOP. Can be
  * replaced by architecture specific code.
  */
-static inline int arch_xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu,
-						      unsigned long ti_work);
+static inline int arch_xfer_to_guest_mode_handle_work(unsigned long ti_work);
 
 #ifndef arch_xfer_to_guest_mode_work
-static inline int arch_xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu,
-						      unsigned long ti_work)
+static inline int arch_xfer_to_guest_mode_handle_work(unsigned long ti_work)
 {
 	return 0;
 }
@@ -46,11 +42,10 @@ static inline int arch_xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu,
 /**
  * xfer_to_guest_mode_handle_work - Check and handle pending work which needs
  *				    to be handled before going to guest mode
- * @vcpu:	Pointer to current's VCPU data
  *
  * Returns: 0 or an error code
  */
-int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu);
+int xfer_to_guest_mode_handle_work(void);
 
 /**
  * xfer_to_guest_mode_prepare - Perform last minute preparation work that
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 15656b7fba6c..598b9473e46d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2,7 +2,7 @@
 #ifndef __KVM_HOST_H
 #define __KVM_HOST_H
 
-
+#include <linux/entry-kvm.h>
 #include <linux/types.h>
 #include <linux/hardirq.h>
 #include <linux/list.h>
@@ -2450,6 +2450,17 @@ static inline void kvm_handle_signal_exit(struct kvm_vcpu *vcpu)
 	vcpu->run->exit_reason = KVM_EXIT_INTR;
 	vcpu->stat.signal_exits++;
 }
+
+static inline int kvm_xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
+{
+	int r = xfer_to_guest_mode_handle_work();
+
+	if (r) {
+		WARN_ON_ONCE(r != -EINTR);
+		kvm_handle_signal_exit(vcpu);
+	}
+	return r;
+}
 #endif /* CONFIG_KVM_XFER_TO_GUEST_WORK */
 
 /*
diff --git a/kernel/entry/kvm.c b/kernel/entry/kvm.c
index 8485f63863af..6fc762eaacca 100644
--- a/kernel/entry/kvm.c
+++ b/kernel/entry/kvm.c
@@ -1,17 +1,14 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/entry-kvm.h>
-#include <linux/kvm_host.h>
 
-static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
+static int xfer_to_guest_mode_work(unsigned long ti_work)
 {
 	do {
 		int ret;
 
-		if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
-			kvm_handle_signal_exit(vcpu);
+		if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 			return -EINTR;
-		}
 
 		if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY))
 			schedule();
@@ -19,7 +16,7 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
 		if (ti_work & _TIF_NOTIFY_RESUME)
 			resume_user_mode_work(NULL);
 
-		ret = arch_xfer_to_guest_mode_handle_work(vcpu, ti_work);
+		ret = arch_xfer_to_guest_mode_handle_work(ti_work);
 		if (ret)
 			return ret;
 
@@ -28,7 +25,7 @@ static int xfer_to_guest_mode_work(struct kvm_vcpu *vcpu, unsigned long ti_work)
 	return 0;
 }
 
-int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
+int xfer_to_guest_mode_handle_work(void)
 {
 	unsigned long ti_work;
 
@@ -44,6 +41,6 @@ int xfer_to_guest_mode_handle_work(struct kvm_vcpu *vcpu)
 	if (!(ti_work & XFER_TO_GUEST_MODE_WORK))
 		return 0;
 
-	return xfer_to_guest_mode_work(vcpu, ti_work);
+	return xfer_to_guest_mode_work(ti_work);
 }
 EXPORT_SYMBOL_GPL(xfer_to_guest_mode_handle_work);
-- 
2.51.0.268.g9569e192d0-goog