Merge remote-tracking branch 'asoc/for-5.10' into asoc-linus

1 files changed, 9 insertions, 6 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 6e3e8a124903..82bf37a5c9ec 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1128,7 +1128,7 @@ access_error(unsigned long error_code, struct vm_area_struct *vma)
 	return 0;
 }
 
-static int fault_in_kernel_space(unsigned long address)
+bool fault_in_kernel_space(unsigned long address)
 {
 	/*
 	 * On 64-bit systems, the vsyscall page is at an address above
@@ -1446,11 +1446,14 @@ DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault)
 	prefetchw(&current->mm->mmap_lock);
 
 	/*
-	 * KVM has two types of events that are, logically, interrupts, but
-	 * are unfortunately delivered using the #PF vector.  These events are
-	 * "you just accessed valid memory, but the host doesn't have it right
-	 * now, so I'll put you to sleep if you continue" and "that memory
-	 * you tried to access earlier is available now."
+	 * KVM uses #PF vector to deliver 'page not present' events to guests
+	 * (asynchronous page fault mechanism). The event happens when a
+	 * userspace task is trying to access some valid (from guest's point of
+	 * view) memory which is not currently mapped by the host (e.g. the
+	 * memory is swapped out). Note, the corresponding "page ready" event
+	 * which is injected when the memory becomes available, is delived via
+	 * an interrupt mechanism and not a #PF exception
+	 * (see arch/x86/kernel/kvm.c: sysvec_kvm_asyncpf_interrupt()).
 	 *
 	 * We are relying on the interrupted context being sane (valid RSP,
 	 * relevant locks not held, etc.), which is fine as long as the