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

[Heiko Carstens <hca@linux.ibm.com>]

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@linux.ibm.com>
> Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>
> ---
>  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.