[PATCH v8 03/17] KVM: s390: pv: handle secure storage exceptions for normal guests

[Claudio Imbrenda]

With upcoming patches, normal guests might touch secure pages.

This patch extends the existing exception handler to convert the pages
to non secure also when the exception is triggered by a normal guest.

This can happen for example when a secure guest reboots; the first
stage of a secure guest is non secure, and in general a secure guest
can reboot into non-secure mode.

If the secure memory of the previous boot has not been cleared up
completely yet (which will be allowed to happen in an upcoming patch),
a non-secure guest might touch secure memory, which will need to be
handled properly.

Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
---
 arch/s390/mm/fault.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 47b52e5384f8..54571a88a641 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -770,6 +770,7 @@ void do_secure_storage_access(struct pt_regs *regs)
 	struct vm_area_struct *vma;
 	struct mm_struct *mm;
 	struct page *page;
+	struct gmap *gmap;
 	int rc;
 
 	/*
@@ -799,6 +800,17 @@ void do_secure_storage_access(struct pt_regs *regs)
 	}
 
 	switch (get_fault_type(regs)) {
+	case GMAP_FAULT:
+		mm = current->mm;
+		gmap = (struct gmap *)S390_lowcore.gmap;
+		mmap_read_lock(mm);
+		addr = __gmap_translate(gmap, addr);
+		mmap_read_unlock(mm);
+		if (IS_ERR_VALUE(addr)) {
+			do_fault_error(regs, VM_ACCESS_FLAGS, VM_FAULT_BADMAP);
+			break;
+		}
+		fallthrough;
 	case USER_FAULT:
 		mm = current->mm;
 		mmap_read_lock(mm);
@@ -827,7 +839,6 @@ void do_secure_storage_access(struct pt_regs *regs)
 		if (rc)
 			BUG();
 		break;
-	case GMAP_FAULT:
 	default:
 		do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
 		WARN_ON_ONCE(1);
-- 
2.34.1