Re: [PATCH 3/3] kvm: s390: Fix lpsw/e spec exception ilc reporting

Heiko Carstens
2026-04-23T13:36:11Z

On Thu, Apr 23, 2026 at 12:36:04PM +0000, Janosch Frank wrote:
> On early PSW specification exception the ILC has to be 0 according to
> architecture.
>
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> Fixes: 48a3e950f4cee ("KVM: s390: Add support for machine checks.")
> ---
> arch/s390/kvm/priv.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 56e63679f9d1..9fd7d3f1d1e8 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -713,6 +713,7 @@ int is_valid_psw(psw_t *psw)
> int kvm_s390_handle_lpsw(struct kvm_vcpu *vcpu)
> {
> psw_t *gpsw = &vcpu->arch.sie_block->gpsw;
> + struct kvm_s390_pgm_info info = {};
> psw32_t new_psw;
> u64 addr, iaddr;
> int rc;
> @@ -738,14 +739,18 @@ int kvm_s390_handle_lpsw(struct kvm_vcpu *vcpu)
> gpsw->addr = new_psw.addr & ~PSW32_ADDR_AMODE;
> vcpu->arch.sie_block->gbea = iaddr;
>
> - if (!is_valid_psw(gpsw))
> - return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
> + if (!is_valid_psw(gpsw)) {
> + info.code = PGM_SPECIFICATION;
> + info.flags = KVM_S390_PGM_FLAGS_ILC_VALID;
> + return kvm_s390_inject_prog_irq(vcpu, &info);
> + }

Hmm... looking at the architecture: an odd instruction address in the PSW
does not result in an early specification exception, but a "normal"
specification exception. is_valid_psw() however also checks for an odd
instruction address. So I guess this is still not entirely correct.

I'm also wondering if the above implementation is correct if PER is enabled
when the specification happens...

Btw.: you may want to have consistent short descriptions for your two
patches. That is consistently use upper or lower case for "LPSW/E".