Re: [PATCH v7 22/23] KVM: s390: arm64: Implement basic page fault handler

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] Unused local variable 'esr' and unused parameters 'slot' and 'hva'.
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commit 0b610e782223a98a4d9a93986b45a74687aeae46
Author: Steffen Eiden <seiden@linux.ibm.com>

KVM: s390: arm64: Implement basic page fault handler

This commit adds host functionality to page in guest memory. If the guest does
something unexpected or illegal, it exits to userspace and aborts execution.

[ ... ]
> diff --git a/arch/s390/kvm/arm64/mmu.c b/arch/s390/kvm/arm64/mmu.c
> new file mode 100644
> index 0000000000000..bf3442d3609b2
> --- /dev/null
> +++ b/arch/s390/kvm/arm64/mmu.c
> @@ -0,0 +1,177 @@
[ ... ]
> +/*
> + * user_mem_abort() - handle a dat fault for the gmap of a vcpu
> + *
> + * Return: 0 on success, < 0 in case of error.
> + * Context: The mm lock must not be held before calling. May sleep.
> + */
> +static int user_mem_abort(struct kvm_vcpu *vcpu, gpa_t fault_ipa,
> +			  struct kvm_memory_slot *slot, hva_t hva)
> +{

[Severity: Low]
Are the slot and hva parameters needed for user_mem_abort in
arch/s390/kvm/arm64/mmu.c? They are passed into the function but never accessed
inside the function body. Could they be removed to avoid unused parameter
warnings?

> +	struct guest_fault f = { };
> +	int ret;
> +
> +	if (kvm_s390_cur_gmap_fault_is_write(vcpu))
> +		f.write_attempt = FOLL_WRITE;
> +	f.gfn = gpa_to_gfn(fault_ipa);
> +
> +	ret = kvm_s390_faultin_gfn(vcpu, NULL, &f);
[ ... ]
> +int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_memory_slot *memslot;
> +	bool translation = false;
> +	phys_addr_t fault_ipa;
> +	unsigned long esr;
> +	unsigned long hva;
> +	bool write_fault;
> +	bool guest_size_err;
> +	bool writable;
> +	bool is_iabt;
> +	int ret;
> +	gfn_t gfn;
> +	int idx;
> +
> +	esr = kvm_vcpu_get_esr(vcpu);

[Severity: Low]
Is the esr variable needed here? It is assigned the result of
kvm_vcpu_get_esr(vcpu) in kvm_handle_guest_abort(), but it is never
evaluated subsequently in the function.

> +	fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
> +	is_iabt = kvm_vcpu_trap_is_iabt(vcpu);
> +	guest_size_err = vcpu->arch.sae_block.icptr == SAE_ICPTR_GUEST_ADDRESS_SIZE;
[ ... ]

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Sashiko AI review · https://sashiko.dev/#/patchset/20260831144802.834315-1-seiden@linux.ibm.com?part=22