On Thu, 12 May 2022 15:10:17 +0200
Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx> wrote:
> If user space uses a memop to emulate an instruction and that
> memop fails, the execution of the instruction ends.
> Instruction execution can end in different ways, one of which is
> suppression, which requires that the instruction execute like a no-op.
> A writing memop that spans multiple pages and fails due to key
> protection may have modified guest memory, as a result, the likely
> correct ending is termination. Therefore, do not indicate a
> suppressing instruction ending in this case.
>
> Signed-off-by: Janis Schoetterl-Glausch <scgl@xxxxxxxxxxxxx>
Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> ---
> Documentation/virt/kvm/api.rst | 6 ++++++
> arch/s390/kvm/gaccess.c | 22 ++++++++++++++++++----
> 2 files changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 4a900cdbc62e..b6aba4f50db7 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -3754,12 +3754,18 @@ in case of KVM_S390_MEMOP_F_CHECK_ONLY), the ioctl returns a positive
> error number indicating the type of exception. This exception is also
> raised directly at the corresponding VCPU if the flag
> KVM_S390_MEMOP_F_INJECT_EXCEPTION is set.
> +On protection exceptions, unless specified otherwise, the injected
> +translation-exception identifier (TEID) indicates suppression.
>
> If the KVM_S390_MEMOP_F_SKEY_PROTECTION flag is set, storage key
> protection is also in effect and may cause exceptions if accesses are
> prohibited given the access key designated by "key"; the valid range is 0..15.
> KVM_S390_MEMOP_F_SKEY_PROTECTION is available if KVM_CAP_S390_MEM_OP_EXTENSION
> is > 0.
> +Since the accessed memory may span multiple pages and those pages might have
> +different storage keys, it is possible that a protection exception occurs
> +after memory has been modified. In this case, if the exception is injected,
> +the TEID does not indicate suppression.
>
> Absolute read/write:
> ^^^^^^^^^^^^^^^^^^^^
> diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
> index d53a183c2005..227ed0009354 100644
> --- a/arch/s390/kvm/gaccess.c
> +++ b/arch/s390/kvm/gaccess.c
> @@ -491,8 +491,8 @@ enum prot_type {
> PROT_TYPE_IEP = 4,
> };
>
> -static int trans_exc(struct kvm_vcpu *vcpu, int code, unsigned long gva,
> - u8 ar, enum gacc_mode mode, enum prot_type prot)
> +static int trans_exc_ending(struct kvm_vcpu *vcpu, int code, unsigned long gva, u8 ar,
> + enum gacc_mode mode, enum prot_type prot, bool terminate)
> {
> struct kvm_s390_pgm_info *pgm = &vcpu->arch.pgm;
> struct trans_exc_code_bits *tec;
> @@ -520,6 +520,11 @@ static int trans_exc(struct kvm_vcpu *vcpu, int code, unsigned long gva,
> tec->b61 = 1;
> break;
> }
> + if (terminate) {
> + tec->b56 = 0;
> + tec->b60 = 0;
> + tec->b61 = 0;
> + }
> fallthrough;
> case PGM_ASCE_TYPE:
> case PGM_PAGE_TRANSLATION:
> @@ -552,6 +557,12 @@ static int trans_exc(struct kvm_vcpu *vcpu, int code, unsigned long gva,
> return code;
> }
>
> +static int trans_exc(struct kvm_vcpu *vcpu, int code, unsigned long gva, u8 ar,
> + enum gacc_mode mode, enum prot_type prot)
> +{
> + return trans_exc_ending(vcpu, code, gva, ar, mode, prot, false);
> +}
> +
> static int get_vcpu_asce(struct kvm_vcpu *vcpu, union asce *asce,
> unsigned long ga, u8 ar, enum gacc_mode mode)
> {
> @@ -1109,8 +1120,11 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
> data += fragment_len;
> ga = kvm_s390_logical_to_effective(vcpu, ga + fragment_len);
> }
> - if (rc > 0)
> - rc = trans_exc(vcpu, rc, ga, ar, mode, prot);
> + if (rc > 0) {
> + bool terminate = (mode == GACC_STORE) && (idx > 0);
> +
> + rc = trans_exc_ending(vcpu, rc, ga, ar, mode, prot, terminate);
> + }
> out_unlock:
> if (need_ipte_lock)
> ipte_unlock(vcpu);
