[PATCH 08/15] arm/arm64: KVM: Always have merged page tables

[Christoffer Dall]

On Tue, Jun 07, 2016 at 11:58:28AM +0100, Marc Zyngier wrote:
> We're in a position where we can now always have "merged" page
> tables, where both the runtime mapping and the idmap coexist.
> 
> This results in some code being removed, but there is more to come.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> ---
>  arch/arm/kvm/mmu.c     | 74 +++++++++++++++++++++++---------------------------
>  arch/arm64/kvm/reset.c | 31 +++++----------------
>  2 files changed, 41 insertions(+), 64 deletions(-)
> 
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index d6ecbf1..9a17e14 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -492,13 +492,12 @@ void free_boot_hyp_pgd(void)
>  
>  	if (boot_hyp_pgd) {
>  		unmap_hyp_range(boot_hyp_pgd, hyp_idmap_start, PAGE_SIZE);
> -		unmap_hyp_range(boot_hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);
>  		free_pages((unsigned long)boot_hyp_pgd, hyp_pgd_order);
>  		boot_hyp_pgd = NULL;
>  	}
>  
>  	if (hyp_pgd)
> -		unmap_hyp_range(hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);
> +		unmap_hyp_range(hyp_pgd, hyp_idmap_start, PAGE_SIZE);
>  
>  	mutex_unlock(&kvm_hyp_pgd_mutex);
>  }
> @@ -1690,7 +1689,7 @@ phys_addr_t kvm_mmu_get_boot_httbr(void)
>  	if (__kvm_cpu_uses_extended_idmap())
>  		return virt_to_phys(merged_hyp_pgd);
>  	else
> -		return virt_to_phys(boot_hyp_pgd);
> +		return virt_to_phys(hyp_pgd);
>  }
>  
>  phys_addr_t kvm_get_idmap_vector(void)
> @@ -1703,6 +1702,22 @@ phys_addr_t kvm_get_idmap_start(void)
>  	return hyp_idmap_start;
>  }
>  
> +static int kvm_map_idmap_text(pgd_t *pgd)
> +{
> +	int err;
> +
> +	/* Create the idmap in the boot page tables */
> +	err = 	__create_hyp_mappings(pgd,
> +				      hyp_idmap_start, hyp_idmap_end,
> +				      __phys_to_pfn(hyp_idmap_start),
> +				      PAGE_HYP);
> +	if (err)
> +		kvm_err("Failed to idmap %lx-%lx\n",
> +			hyp_idmap_start, hyp_idmap_end);
> +
> +	return err;
> +}
> +
>  int kvm_mmu_init(void)
>  {
>  	int err;
> @@ -1718,27 +1733,25 @@ int kvm_mmu_init(void)
>  	BUG_ON((hyp_idmap_start ^ (hyp_idmap_end - 1)) & PAGE_MASK);
>  
>  	hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, hyp_pgd_order);
> -	boot_hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, hyp_pgd_order);
> -
> -	if (!hyp_pgd || !boot_hyp_pgd) {
> +	if (!hyp_pgd) {
>  		kvm_err("Hyp mode PGD not allocated\n");
>  		err = -ENOMEM;
>  		goto out;
>  	}
>  
> -	/* Create the idmap in the boot page tables */
> -	err = 	__create_hyp_mappings(boot_hyp_pgd,
> -				      hyp_idmap_start, hyp_idmap_end,
> -				      __phys_to_pfn(hyp_idmap_start),
> -				      PAGE_HYP);
> +	if (__kvm_cpu_uses_extended_idmap()) {
> +		boot_hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
> +							 hyp_pgd_order);
> +		if (!boot_hyp_pgd) {
> +			kvm_err("Hyp boot PGD not allocated\n");
> +			err = -ENOMEM;
> +			goto out;
> +		}
>  
> -	if (err) {
> -		kvm_err("Failed to idmap %lx-%lx\n",
> -			hyp_idmap_start, hyp_idmap_end);
> -		goto out;
> -	}
> +		err = kvm_map_idmap_text(boot_hyp_pgd);
> +		if (err)
> +			goto out;
>  
> -	if (__kvm_cpu_uses_extended_idmap()) {
>  		merged_hyp_pgd = (pgd_t *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
>  		if (!merged_hyp_pgd) {
>  			kvm_err("Failed to allocate extra HYP pgd\n");
> @@ -1746,29 +1759,10 @@ int kvm_mmu_init(void)
>  		}
>  		__kvm_extend_hypmap(boot_hyp_pgd, hyp_pgd, merged_hyp_pgd,
>  				    hyp_idmap_start);
> -		return 0;
> -	}
> -
> -	/* Map the very same page at the trampoline VA */
> -	err = 	__create_hyp_mappings(boot_hyp_pgd,
> -				      TRAMPOLINE_VA, TRAMPOLINE_VA + PAGE_SIZE,
> -				      __phys_to_pfn(hyp_idmap_start),
> -				      PAGE_HYP);
> -	if (err) {
> -		kvm_err("Failed to map trampoline @%lx into boot HYP pgd\n",
> -			TRAMPOLINE_VA);
> -		goto out;
> -	}
> -
> -	/* Map the same page again into the runtime page tables */
> -	err = 	__create_hyp_mappings(hyp_pgd,
> -				      TRAMPOLINE_VA, TRAMPOLINE_VA + PAGE_SIZE,
> -				      __phys_to_pfn(hyp_idmap_start),
> -				      PAGE_HYP);
> -	if (err) {
> -		kvm_err("Failed to map trampoline @%lx into runtime HYP pgd\n",
> -			TRAMPOLINE_VA);
> -		goto out;
> +	} else {
> +		err = kvm_map_idmap_text(hyp_pgd);
> +		if (err)
> +			goto out;

Something I'm not clear on:

how can we always have merged pgtables on 32-bit ARM at this point?

why is there not a potential conflict at this point in the series
between the runtime hyp mappings and the idmaps?

Thanks,
-Christoffer