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

Thomas Huth
2024-06-27T09:44:59Z

On 27/06/2024 11.05, 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(+)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 95990461888f..9281063636a7 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -427,6 +427,7 @@ struct kvm_vcpu_stat {
> u64 instruction_io_other;
> u64 instruction_lpsw;
> u64 instruction_lpswe;
> + u64 instruction_lpswey;
> u64 instruction_pfmf;
> u64 instruction_ptff;
> u64 instruction_sck;
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 50b77b759042..8e04c7f0c90c 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -132,6 +132,7 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
> STATS_DESC_COUNTER(VCPU, instruction_io_other),
> STATS_DESC_COUNTER(VCPU, instruction_lpsw),
> STATS_DESC_COUNTER(VCPU, instruction_lpswe),
> + STATS_DESC_COUNTER(VCPU, instruction_lpswey),
> STATS_DESC_COUNTER(VCPU, instruction_pfmf),
> STATS_DESC_COUNTER(VCPU, instruction_ptff),
> STATS_DESC_COUNTER(VCPU, instruction_sck),
> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
> index 111eb5c74784..c61966cae121 100644
> --- a/arch/s390/kvm/kvm-s390.h
> +++ b/arch/s390/kvm/kvm-s390.h
> @@ -138,6 +138,22 @@ static inline u64 kvm_s390_get_base_disp_s(struct kvm_vcpu *vcpu, u8 *ar)
> return (base2 ? vcpu->run->s.regs.gprs[base2] : 0) + disp2;
> }
>
> +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);

Quoting the Principles of Operations:

"If the storage-key-removal facility is installed, a spe-
cial-operation exception is recognized if the key value
in bits 8-11 of the storage operand is nonzero."

Do we need to have such a check here, too?

Thomas

> + 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;
> +}
> +
> static int handle_stidp(struct kvm_vcpu *vcpu)
> {
> u64 stidp_data = vcpu->kvm->arch.model.cpuid;
> @@ -1462,6 +1492,8 @@ int kvm_s390_handle_eb(struct kvm_vcpu *vcpu)
> case 0x61:
> case 0x62:
> return handle_ri(vcpu);
> + case 0x71:
> + return handle_lpswey(vcpu);
> default:
> return -EOPNOTSUPP;
> }