linux-kernel - [PATCH AUTOSEL 5.6 102/149] selftests: KVM: s390: fix early guest crash

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Date:   Sat, 11 Apr 2020 19:02:59 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Christian Borntraeger <borntraeger@...ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>, kvm@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: [PATCH AUTOSEL 5.6 102/149] selftests: KVM: s390: fix early guest crash

From: Christian Borntraeger <borntraeger@...ibm.com>

[ Upstream commit 41cbed5b07b5f6ca4ae567059ae7f0ffad1fd454 ]

The guest crashes very early due to changes in the control registers
used by dynamic address translation. Let us use different registers
that will not crash the guest.

Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/testing/selftests/kvm/s390x/resets.c | 27 +++++++++++-----------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/tools/testing/selftests/kvm/s390x/resets.c b/tools/testing/selftests/kvm/s390x/resets.c
index 1485bc6c8999f..cbb343ad5d424 100644
--- a/tools/testing/selftests/kvm/s390x/resets.c
+++ b/tools/testing/selftests/kvm/s390x/resets.c
@@ -23,25 +23,24 @@ struct kvm_run *run;
 struct kvm_sync_regs *regs;
 static uint64_t regs_null[16];
 
-static uint64_t crs[16] = { 0x40000ULL,
-			    0x42000ULL,
-			    0, 0, 0, 0, 0,
-			    0x43000ULL,
-			    0, 0, 0, 0, 0,
-			    0x44000ULL,
-			    0, 0
-};
-
 static void guest_code_initial(void)
 {
-	/* Round toward 0 */
-	uint32_t fpc = 0x11;
+	/* set several CRs to "safe" value */
+	unsigned long cr2_59 = 0x10;	/* enable guarded storage */
+	unsigned long cr8_63 = 0x1;	/* monitor mask = 1 */
+	unsigned long cr10 = 1;		/* PER START */
+	unsigned long cr11 = -1;	/* PER END */
+
 
 	/* Dirty registers */
 	asm volatile (
-		"	lctlg	0,15,%0\n"
-		"	sfpc	%1\n"
-		: : "Q" (crs), "d" (fpc));
+		"	lghi	2,0x11\n"	/* Round toward 0 */
+		"	sfpc	2\n"		/* set fpc to !=0 */
+		"	lctlg	2,2,%0\n"
+		"	lctlg	8,8,%1\n"
+		"	lctlg	10,10,%2\n"
+		"	lctlg	11,11,%3\n"
+		: : "m" (cr2_59), "m" (cr8_63), "m" (cr10), "m" (cr11) : "2");
 	GUEST_SYNC(0);
 }
 
-- 
2.20.1