Re: [PATCH 1/2] arm/arm64: kvm: drop inappropriate use of kvm_is_mmio_pfn()

[Christoffer Dall <christoffer.dall@linaro.org>]

On Mon, Nov 10, 2014 at 09:33:55AM +0100, Ard Biesheuvel wrote:
> Instead of using kvm_is_mmio_pfn() to decide whether a host region
> should be stage 2 mapped with device attributes, add a new static
> function kvm_is_device_pfn() that disregards RAM pages with the
> reserved bit set, as those should usually not be mapped as device
> memory.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  arch/arm/kvm/mmu.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 57a403a5c22b..b007438242e2 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -834,6 +834,11 @@ static bool kvm_is_write_fault(struct kvm_vcpu *vcpu)
>  	return kvm_vcpu_dabt_iswrite(vcpu);
>  }
>  
> +static bool kvm_is_device_pfn(unsigned long pfn)
> +{
> +	return !pfn_valid(pfn);
> +}

So this works for Magnus' use case, because a device tree memreserve
results in reserved, but valid, existing pages being backed by a struct
page?

> +
>  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)
> @@ -904,7 +909,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	if (is_error_pfn(pfn))
>  		return -EFAULT;
>  
> -	if (kvm_is_mmio_pfn(pfn))
> +	if (kvm_is_device_pfn(pfn))
>  		mem_type = PAGE_S2_DEVICE;
>  
>  	spin_lock(&kvm->mmu_lock);
> -- 
> 1.8.3.2
> 

If my understanding above is correct, then:

Acked-by: Christoffer Dall <christoffer.dall@linaro.org>