linux-kernel - Re: [PATCH 3/6] xen/x86/pvh: Properly set page tables for 32-bit PVH guests

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Date:	Tue, 7 Jul 2015 15:31:28 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:	david.vrabel@...rix.com, roger.pau@...rix.com,
	elena.ufimtseva@...cle.com, stefano.stabellini@...citrix.com,
	tim@....org, jbeulich@...e.com, andrew.cooper3@...rix.com,
	ian.campbell@...rix.com, wei.liu2@...rix.com,
	ian.jackson@...citrix.com, xen-devel@...ts.xenproject.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] xen/x86/pvh: Properly set page tables for 32-bit PVH
 guests

On Mon, Jul 06, 2015 at 11:34:22PM -0400, Boris Ostrovsky wrote:
> 32-bit PVH guests don't want to write-protect/pin page tables.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
>  arch/x86/xen/mmu.c | 22 +++++++++++++---------
>  1 file changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index dd151b2..b473df8 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -1762,8 +1762,9 @@ void __init xen_setup_machphys_mapping(void)
>  		machine_to_phys_nr = MACH2PHYS_NR_ENTRIES;
>  	}
>  #ifdef CONFIG_X86_32
> -	WARN_ON((machine_to_phys_mapping + (machine_to_phys_nr - 1))
> -		< machine_to_phys_mapping);
> +	if (!xen_feature(XENFEAT_auto_translated_physmap))
> +		WARN_ON((machine_to_phys_mapping + (machine_to_phys_nr - 1))
> +			< machine_to_phys_mapping);
>  #endif
>  }
>  
> @@ -1958,15 +1959,18 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
>  	initial_page_table[KERNEL_PGD_BOUNDARY] =
>  		__pgd(__pa(initial_kernel_pmd) | _PAGE_PRESENT);
>  
> -	set_page_prot(initial_kernel_pmd, PAGE_KERNEL_RO);
> -	set_page_prot(initial_page_table, PAGE_KERNEL_RO);
> -	set_page_prot(empty_zero_page, PAGE_KERNEL_RO);
> +	if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> +		set_page_prot(initial_kernel_pmd, PAGE_KERNEL_RO);
> +		set_page_prot(initial_page_table, PAGE_KERNEL_RO);
> +		set_page_prot(empty_zero_page, PAGE_KERNEL_RO);
>  
> -	pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
> +		pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
>  
> -	pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE,
> -			  PFN_DOWN(__pa(initial_page_table)));
> -	xen_write_cr3(__pa(initial_page_table));
> +		pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE,
> +				  PFN_DOWN(__pa(initial_page_table)));
> +		xen_write_cr3(__pa(initial_page_table));
> +	} else
> +		native_write_cr3(__pa(initial_page_table));
>  
>  	memblock_reserve(__pa(xen_start_info->pt_base),
>  			 xen_start_info->nr_pt_frames * PAGE_SIZE);
> -- 
> 1.8.1.4
> 
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