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

Christian Borntraeger
2024-06-28T14:53:29Z

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@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.

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