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

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Am 27.06.24 um 11:57 schrieb Heiko Carstens:
On Thu, Jun 27, 2024 at 11:05:20AM +0200, 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(+)

...

+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;
+}

You may want to use sign_extend32() or sign_extend64() instead of open-coding.

Something like sign_extend64(disp1, 31)
I actually find that harder to read, but I am open for other opinions.








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