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

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Am 27.06.24 um 11:23 schrieb Claudio Imbrenda:
On Thu, 27 Jun 2024 11:05:20 +0200
Christian Borntraeger <borntraeger@xxxxxxxxxxxxx> 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>

[...]

+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);
+
+	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;
+}

looks quite straightforward, but you duplicated most of handle_lpswe.
it would probably be cleaner to abstract the "load psw" logic, and
convert handle_lpswe{,y} to be wrappers around it, something like

static int _handle_load_psw(struct kvm_vcpu *vcpu, unsigned long
pswaddr)

which can then contain the old code from the "if (addr & 7)" to the end
of the function.



I think it would look cleaner, but I don't have a super strong opinion
about it

As this is a functional fix needed to properly run z16 code I would like to
minimize refactoring. I think we also need a different fix for LPSW(E) (we
should set the BEAR register).  We can do refactoring after we have fixed
everything.




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