Re: [PATCH v2] KVM: s390: fix LPSWEY handling

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Am 01.07.24 um 08:08 schrieb Sven Schnelle:
Christian Borntraeger <borntraeger@xxxxxxxxxxxxx> writes:

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         | 15 +++++++++++++++
  arch/s390/kvm/priv.c             | 32 ++++++++++++++++++++++++++++++++
  4 files changed, 49 insertions(+)

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);
+
+	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);

Shouldn't the gpsw get updated with new_psw after the check? POP says "The operation
is suppressed on all addressing and protection exceptions."

Only for exception of the instruction but not for the target PSW.
POP says:

The other PSW fields which are to be loaded by the
instruction are not checked for validity before they are
loaded. However, immediately after loading, a speci-
fication exception is recognized, and a program inter-
ruption occurs, when any of the following is true for
the newly loaded PSW




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