linux-kernel - [PATCH v1 04/11] KVM: s390: pv: handle secure storage exceptions for normal guests

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Date:   Mon, 17 May 2021 22:07:51 +0200
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     kvm@...r.kernel.org
Cc:     cohuck@...hat.com, borntraeger@...ibm.com, frankja@...ux.ibm.com,
        thuth@...hat.com, pasic@...ux.ibm.com, david@...hat.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1 04/11] KVM: s390: pv: handle secure storage exceptions for normal guests

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.

Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
---
 arch/s390/mm/fault.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index efdef35bc415..24a39457cd48 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -789,9 +789,20 @@ 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;
 
 	switch (get_fault_type(regs)) {
+	case GMAP_FAULT:
+		gmap = (struct gmap *)S390_lowcore.gmap;
+		/*
+		 * Very unlikely, but if it happens, simply try again.
+		 * The next attempt will trigger a different exception.
+		 */
+		addr = __gmap_translate(gmap, addr);
+		if (addr == -EFAULT)
+			break;
+		fallthrough;
 	case USER_FAULT:
 		mm = current->mm;
 		mmap_read_lock(mm);
@@ -820,7 +831,6 @@ 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);
-- 
2.31.1