1 files changed, 31 insertions, 19 deletions

diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 5d6ae0326d9e..b2066fbb6341 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -28,7 +28,11 @@ struct vsie_page {
 	 * the same offset as that in struct sie_page!
 	 */
 	struct mcck_volatile_info mcck_info;    /* 0x0200 */
-	/* the pinned originial scb */
+	/*
+	 * The pinned original scb. Be aware that other VCPUs can modify
+	 * it while we read from it. Values that are used for conditions or
+	 * are reused conditionally, should be accessed via READ_ONCE.
+	 */
 	struct kvm_s390_sie_block *scb_o;	/* 0x0218 */
 	/* the shadow gmap in use by the vsie_page */
 	struct gmap *gmap;			/* 0x0220 */
@@ -140,12 +144,13 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 {
 	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
 	struct kvm_s390_sie_block *scb_o = vsie_page->scb_o;
-	u32 crycb_addr = scb_o->crycbd & 0x7ffffff8U;
+	const uint32_t crycbd_o = READ_ONCE(scb_o->crycbd);
+	const u32 crycb_addr = crycbd_o & 0x7ffffff8U;
 	unsigned long *b1, *b2;
 	u8 ecb3_flags;
 
 	scb_s->crycbd = 0;
-	if (!(scb_o->crycbd & vcpu->arch.sie_block->crycbd & CRYCB_FORMAT1))
+	if (!(crycbd_o & vcpu->arch.sie_block->crycbd & CRYCB_FORMAT1))
 		return 0;
 	/* format-1 is supported with message-security-assist extension 3 */
 	if (!test_kvm_facility(vcpu->kvm, 76))
@@ -183,12 +188,15 @@ static void prepare_ibc(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 {
 	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
 	struct kvm_s390_sie_block *scb_o = vsie_page->scb_o;
+	/* READ_ONCE does not work on bitfields - use a temporary variable */
+	const uint32_t __new_ibc = scb_o->ibc;
+	const uint32_t new_ibc = READ_ONCE(__new_ibc) & 0x0fffU;
 	__u64 min_ibc = (sclp.ibc >> 16) & 0x0fffU;
 
 	scb_s->ibc = 0;
 	/* ibc installed in g2 and requested for g3 */
-	if (vcpu->kvm->arch.model.ibc && (scb_o->ibc & 0x0fffU)) {
-		scb_s->ibc = scb_o->ibc & 0x0fffU;
+	if (vcpu->kvm->arch.model.ibc && new_ibc) {
+		scb_s->ibc = new_ibc;
 		/* takte care of the minimum ibc level of the machine */
 		if (scb_s->ibc < min_ibc)
 			scb_s->ibc = min_ibc;
@@ -253,6 +261,10 @@ static int shadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 {
 	struct kvm_s390_sie_block *scb_o = vsie_page->scb_o;
 	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
+	/* READ_ONCE does not work on bitfields - use a temporary variable */
+	const uint32_t __new_prefix = scb_o->prefix;
+	const uint32_t new_prefix = READ_ONCE(__new_prefix);
+	const bool wants_tx = READ_ONCE(scb_o->ecb) & ECB_TE;
 	bool had_tx = scb_s->ecb & ECB_TE;
 	unsigned long new_mso = 0;
 	int rc;
@@ -299,14 +311,14 @@ static int shadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 	scb_s->icpua = scb_o->icpua;
 
 	if (!(atomic_read(&scb_s->cpuflags) & CPUSTAT_SM))
-		new_mso = scb_o->mso & 0xfffffffffff00000UL;
+		new_mso = READ_ONCE(scb_o->mso) & 0xfffffffffff00000UL;
 	/* if the hva of the prefix changes, we have to remap the prefix */
-	if (scb_s->mso != new_mso || scb_s->prefix != scb_o->prefix)
+	if (scb_s->mso != new_mso || scb_s->prefix != new_prefix)
 		prefix_unmapped(vsie_page);
 	 /* SIE will do mso/msl validity and exception checks for us */
 	scb_s->msl = scb_o->msl & 0xfffffffffff00000UL;
 	scb_s->mso = new_mso;
-	scb_s->prefix = scb_o->prefix;
+	scb_s->prefix = new_prefix;
 
 	/* We have to definetly flush the tlb if this scb never ran */
 	if (scb_s->ihcpu != 0xffffU)
@@ -318,11 +330,11 @@ static int shadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 	if (test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_ESOP))
 		scb_s->ecb |= scb_o->ecb & ECB_HOSTPROTINT;
 	/* transactional execution */
-	if (test_kvm_facility(vcpu->kvm, 73)) {
+	if (test_kvm_facility(vcpu->kvm, 73) && wants_tx) {
 		/* remap the prefix is tx is toggled on */
-		if ((scb_o->ecb & ECB_TE) && !had_tx)
+		if (!had_tx)
 			prefix_unmapped(vsie_page);
-		scb_s->ecb |= scb_o->ecb & ECB_TE;
+		scb_s->ecb |= ECB_TE;
 	}
 	/* SIMD */
 	if (test_kvm_facility(vcpu->kvm, 129)) {
@@ -529,9 +541,9 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 	gpa_t gpa;
 	int rc = 0;
 
-	gpa = scb_o->scaol & ~0xfUL;
+	gpa = READ_ONCE(scb_o->scaol) & ~0xfUL;
 	if (test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_64BSCAO))
-		gpa |= (u64) scb_o->scaoh << 32;
+		gpa |= (u64) READ_ONCE(scb_o->scaoh) << 32;
 	if (gpa) {
 		if (!(gpa & ~0x1fffUL))
 			rc = set_validity_icpt(scb_s, 0x0038U);
@@ -551,7 +563,7 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 		scb_s->scaol = (u32)(u64)hpa;
 	}
 
-	gpa = scb_o->itdba & ~0xffUL;
+	gpa = READ_ONCE(scb_o->itdba) & ~0xffUL;
 	if (gpa && (scb_s->ecb & ECB_TE)) {
 		if (!(gpa & ~0x1fffU)) {
 			rc = set_validity_icpt(scb_s, 0x0080U);
@@ -566,7 +578,7 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 		scb_s->itdba = hpa;
 	}
 
-	gpa = scb_o->gvrd & ~0x1ffUL;
+	gpa = READ_ONCE(scb_o->gvrd) & ~0x1ffUL;
 	if (gpa && (scb_s->eca & ECA_VX) && !(scb_s->ecd & ECD_HOSTREGMGMT)) {
 		if (!(gpa & ~0x1fffUL)) {
 			rc = set_validity_icpt(scb_s, 0x1310U);
@@ -584,7 +596,7 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 		scb_s->gvrd = hpa;
 	}
 
-	gpa = scb_o->riccbd & ~0x3fUL;
+	gpa = READ_ONCE(scb_o->riccbd) & ~0x3fUL;
 	if (gpa && (scb_s->ecb3 & ECB3_RI)) {
 		if (!(gpa & ~0x1fffUL)) {
 			rc = set_validity_icpt(scb_s, 0x0043U);
@@ -602,8 +614,8 @@ static int pin_blocks(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 	if ((scb_s->ecb & ECB_GS) && !(scb_s->ecd & ECD_HOSTREGMGMT)) {
 		unsigned long sdnxc;
 
-		gpa = scb_o->sdnxo & ~0xfUL;
-		sdnxc = scb_o->sdnxo & 0xfUL;
+		gpa = READ_ONCE(scb_o->sdnxo) & ~0xfUL;
+		sdnxc = READ_ONCE(scb_o->sdnxo) & 0xfUL;
 		if (!gpa || !(gpa & ~0x1fffUL)) {
 			rc = set_validity_icpt(scb_s, 0x10b0U);
 			goto unpin;
@@ -768,7 +780,7 @@ static void retry_vsie_icpt(struct vsie_page *vsie_page)
 static int handle_stfle(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
 {
 	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
-	__u32 fac = vsie_page->scb_o->fac & 0x7ffffff8U;
+	__u32 fac = READ_ONCE(vsie_page->scb_o->fac) & 0x7ffffff8U;
 
 	if (fac && test_kvm_facility(vcpu->kvm, 7)) {
 		retry_vsie_icpt(vsie_page);