Subject: [PATCH v6 10/26] KVM: arm/arm64: Fix idmap size and alignment

From: [email-masked] (James Morse)
Date: Thu, 15 Mar 2018 19:15:48 +0000

On 14/03/18 16:50, Marc Zyngier wrote:
> Although the idmap section of KVM can only be at most 4kB and
> must be aligned on a 4kB boundary, the rest of the code expects
> it to be page aligned. Things get messy when tearing down the
> HYP page tables when PAGE_SIZE is 64K, and the idmap section isn't
> 64K aligned.
> 
> Let's fix this by computing aligned boundaries that the HYP code
> will use.

> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> index 0e5cfffb4c21..a9e0513868e9 100644
> --- a/virt/kvm/arm/mmu.c
> +++ b/virt/kvm/arm/mmu.c
> @@ -1815,7 +1815,9 @@ int kvm_mmu_init(void)
>  	int err;
>  
>  	hyp_idmap_start = kvm_virt_to_phys(__hyp_idmap_text_start);
> +	hyp_idmap_start = ALIGN_DOWN(hyp_idmap_start, PAGE_SIZE);
>  	hyp_idmap_end = kvm_virt_to_phys(__hyp_idmap_text_end);
> +	hyp_idmap_end = ALIGN(hyp_idmap_end, PAGE_SIZE);
>  	hyp_idmap_vector = kvm_virt_to_phys(__kvm_hyp_init);
>  
>  	/*

This makes the:
| hyp_idmap_start != (unsigned long)__hyp_idmap_text_start

check below look funny, but that must be for 32bit which only has 4K pages (I
think), so its behaviour hasn't changed.

Reviewed-by: James Morse <[email-masked]>

Thanks,

James