Re: [PATCH 1/1] KVM: s390: fix LPSWEY handling

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On 27/06/2024 11.05, Christian Borntraeger wrote:
in rare cases, e.g. for injecting a machine check we do intercept all
load PSW instructions via ICTL_LPSW. With facility 193 a new variant
LPSWEY was added. KVM needs to handle that as well.

Fixes: a3efa8429266 ("KVM: s390: gen_facilities: allow facilities 165, 193, 194 and 196")
Reported-by: Marc Hartmayer <mhartmay@xxxxxxxxxxxxx>
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
---
  arch/s390/include/asm/kvm_host.h |  1 +
  arch/s390/kvm/kvm-s390.c         |  1 +
  arch/s390/kvm/kvm-s390.h         | 16 ++++++++++++++++
  arch/s390/kvm/priv.c             | 32 ++++++++++++++++++++++++++++++++
  4 files changed, 50 insertions(+)

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 95990461888f..9281063636a7 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -427,6 +427,7 @@ struct kvm_vcpu_stat {
  	u64 instruction_io_other;
  	u64 instruction_lpsw;
  	u64 instruction_lpswe;
+	u64 instruction_lpswey;
  	u64 instruction_pfmf;
  	u64 instruction_ptff;
  	u64 instruction_sck;
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 50b77b759042..8e04c7f0c90c 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -132,6 +132,7 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
  	STATS_DESC_COUNTER(VCPU, instruction_io_other),
  	STATS_DESC_COUNTER(VCPU, instruction_lpsw),
  	STATS_DESC_COUNTER(VCPU, instruction_lpswe),
+	STATS_DESC_COUNTER(VCPU, instruction_lpswey),
  	STATS_DESC_COUNTER(VCPU, instruction_pfmf),
  	STATS_DESC_COUNTER(VCPU, instruction_ptff),
  	STATS_DESC_COUNTER(VCPU, instruction_sck),
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 111eb5c74784..c61966cae121 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -138,6 +138,22 @@ static inline u64 kvm_s390_get_base_disp_s(struct kvm_vcpu *vcpu, u8 *ar)
  	return (base2 ? vcpu->run->s.regs.gprs[base2] : 0) + disp2;
  }
+static inline u64 kvm_s390_get_base_disp_siy(struct kvm_vcpu *vcpu, u8 *ar)
+{
+	u32 base1 = vcpu->arch.sie_block->ipb >> 28;
+	u32 disp1 = ((vcpu->arch.sie_block->ipb & 0x0fff0000) >> 16) +
+			((vcpu->arch.sie_block->ipb & 0xff00) << 4);
+
+	/* The displacement is a 20bit _SIGNED_ value */
+	if (disp1 & 0x80000)
+		disp1+=0xfff00000;
+
+	if (ar)
+		*ar = base1;
+
+	return (base1 ? vcpu->run->s.regs.gprs[base1] : 0) + (long)(int)disp1;
+}
+
  static inline void kvm_s390_get_base_disp_sse(struct kvm_vcpu *vcpu,
  					      u64 *address1, u64 *address2,
  					      u8 *ar_b1, u8 *ar_b2)
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index 1be19cc9d73c..1a49b89706f8 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -797,6 +797,36 @@ static int handle_lpswe(struct kvm_vcpu *vcpu)
  	return 0;
  }
+static int handle_lpswey(struct kvm_vcpu *vcpu)
+{
+	psw_t new_psw;
+	u64 addr;
+	int rc;
+	u8 ar;
+
+	vcpu->stat.instruction_lpswey++;
+
+	if (!test_kvm_facility(vcpu->kvm, 193))
+		return kvm_s390_inject_program_int(vcpu, PGM_OPERATION);
+
+	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
+		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
+
+	addr = kvm_s390_get_base_disp_siy(vcpu, &ar);
+	if (addr & 7)
+		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
+
+	rc = read_guest(vcpu, addr, ar, &new_psw, sizeof(new_psw));
+	if (rc)
+		return kvm_s390_inject_prog_cond(vcpu, rc);

Quoting the Principles of Operations:

"If the storage-key-removal facility is installed, a spe-
cial-operation exception is recognized if the key value
in bits 8-11 of the storage operand is nonzero."

Do we need to have such a check here, too?

 Thomas


+	vcpu->arch.sie_block->gpsw = new_psw;
+	if (!is_valid_psw(&vcpu->arch.sie_block->gpsw))
+		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
+
+	return 0;
+}
+
  static int handle_stidp(struct kvm_vcpu *vcpu)
  {
  	u64 stidp_data = vcpu->kvm->arch.model.cpuid;
@@ -1462,6 +1492,8 @@ int kvm_s390_handle_eb(struct kvm_vcpu *vcpu)
  	case 0x61:
  	case 0x62:
  		return handle_ri(vcpu);
+	case 0x71:
+		return handle_lpswey(vcpu);
  	default:
  		return -EOPNOTSUPP;
  	}





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