[PATCH v5 6/9] KVM: Add a helper function to check if a gpa is in writable memselot

The arch specific code may need to know if a particular gpa is valid and
writable for the shared memory between the host and the guest. Currently,
there are few places where it is used in RISC-V implementation. Given the
nature of the function it may be used for other architectures.
Hence, a common helper function is added.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Atish Patra <redacted>
---
 include/linux/kvm_host.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 15656b7fba6c..eec5cbbcb4b3 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h

@@ -1892,6 +1892,14 @@ static inline bool kvm_is_gpa_in_memslot(struct kvm *kvm, gpa_t gpa)
 	return !kvm_is_error_hva(hva);
 }
 
+static inline bool kvm_is_gpa_in_writable_memslot(struct kvm *kvm, gpa_t gpa)
+{
+	bool writable;
+	unsigned long hva = gfn_to_hva_prot(kvm, gpa_to_gfn(gpa), &writable);
+
+	return !kvm_is_error_hva(hva) && writable;
+}
+
 static inline void kvm_gpc_mark_dirty_in_slot(struct gfn_to_pfn_cache *gpc)
 {
 	lockdep_assert_held(&gpc->lock);

-- 
2.43.0