Re: [PATCH v2] KVM: arm/arm64: Signal SIGBUS when stage2 discovers hwpoison memory

[gengdongjiu <gengdongjiu@huawei.com>]

Hi James,
  I have a comment here:

On 2017/5/25 0:32, James Morse wrote:
> +static void kvm_send_hwpoison_signal(unsigned long address,
> +				     struct vm_area_struct *vma)
> +{
> +	siginfo_t info;
> +
> +	info.si_signo   = SIGBUS;
> +	info.si_errno   = 0;
> +	info.si_code    = BUS_MCEERR_AR;
> +	info.si_addr    = (void __user *)address;
> +
> +	if (is_vm_hugetlb_page(vma))
> +		info.si_addr_lsb = huge_page_shift(hstate_vma(vma));
> +	else
> +		info.si_addr_lsb = PAGE_SHIFT;
> +
> +	send_sig_info(SIGBUS, &info, current);
> +}
> +
>  static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  			  struct kvm_memory_slot *memslot, unsigned long hva,
>  			  unsigned long fault_status)
> @@ -1318,6 +1337,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	smp_rmb();
>  
>  	pfn = gfn_to_pfn_prot(kvm, gfn, write_fault, &writable);
> +	if (pfn == KVM_PFN_ERR_HWPOISON) {
> +		kvm_send_hwpoison_signal(hva, vma);
> +		return 0;
> +	}
I heard from our CPU hardware team, when happen HWpoison, CPU hardware does not record the IPA address in the HPFAR_EL2.
Only when the SEA error is related to the page table walk, the HPFAR_EL2 register is updated.
here we got the pfn/gfn from the register HPFAR_EL2, if CPU does not update the HPFAR_EL2 register, we may can not use this method to get the pfn/gfn.
could you confirm arm's armv8.0/armv8.2 standard CPU also use such design? if so, we may need to use other method to get the gfn/pfn/hva address.


>  	if (is_error_noslot_pfn(pfn))
>  		return -EFAULT;