Re: [PATCH v4 5/7] KVM: s390: Fix handle_{sske,pfmf} under memory pressure

[Christian Borntraeger]

Am 19.06.26 um 17:51 schrieb Claudio Imbrenda:
> Under heavy memory pressure, handle_sske() and handle_pfmf() might
> cause an endless loop if the mmu cache runs empty, the atomic
> allocations fail, and the top-up function also fails. While quite
> unlikely, that scenario is not impossible.
>
> Fix the issue by not ignoring the return value of
> kvm_s390_mmu_cache_topup(), and appropriately returning an error code
> in case of failure.
>
> Fixes: e38c884df921 ("KVM: s390: Switch to new gmap")
> Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>

Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>

> ---
>   arch/s390/kvm/priv.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 447ec7ed423d..9bc6fd02ff77 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -366,7 +366,9 @@ static int handle_sske(struct kvm_vcpu *vcpu)
>   		if (rc > 1)
>   			return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
>   		if (rc == -ENOMEM) {
> -			kvm_s390_mmu_cache_topup(vcpu->arch.mc);
> +			rc = kvm_s390_mmu_cache_topup(vcpu->arch.mc);
> +			if (rc)
> +				return rc;
>   			continue;
>   		}
>   		if (rc < 0)
> @@ -1122,7 +1124,9 @@ static int handle_pfmf(struct kvm_vcpu *vcpu)
>   			if (rc > 1)
>   				return kvm_s390_inject_program_int(vcpu, rc);
>   			if (rc == -ENOMEM) {
> -				kvm_s390_mmu_cache_topup(vcpu->arch.mc);
> +				rc = kvm_s390_mmu_cache_topup(vcpu->arch.mc);
> +				if (rc)
> +					return rc;
>   				continue;
>   			}
>   			if (rc < 0)