linux-kernel - Re: [PATCH] adjust/fix LDT handling for Xen

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Message-ID: <47873959.3000102@gmail.com>
Date:	Fri, 11 Jan 2008 10:39:37 +0100
From:	Jiri Slaby <jirislaby@...il.com>
To:	Jan Beulich <jbeulich@...ell.com>
CC:	Jeremy Fitzhardinge <jeremy@...source.com>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] adjust/fix LDT handling for Xen

On 01/11/2008 10:22 AM, Jan Beulich wrote:
> Don't rely on kmalloc(PAGE_SIZE) returning PAGE_SIZE aligned memory
> (Xen requires GDT *and* LDT to be page-aligned). Using the page
> allocator interface also removes the (albeit small) slab allocator
> overhead. The same change being done for 64-bits for consistency.
> 
> Further, the Xen hypercall interface expects the LDT address to be
> virtual, not machine.
> 
> Signed-off-by: Jan Beulich <jbeulich@...ell.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> 
> ---
>  arch/x86/kernel/ldt_32.c |    7 +++----
>  arch/x86/kernel/ldt_64.c |    7 +++----
>  arch/x86/xen/enlighten.c |    9 +--------
>  3 files changed, 7 insertions(+), 16 deletions(-)
> 
> --- linux-2.6.24-rc7/arch/x86/kernel/ldt_32.c	2008-01-10 16:53:54.000000000 +0100
> +++ 2.6.24-rc7-x86-xen-ldt/arch/x86/kernel/ldt_32.c	2008-01-09 13:59:50.000000000 +0100
[...]
> @@ -73,7 +72,7 @@ static int alloc_ldt(mm_context_t *pc, u
>  		if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE)
>  			vfree(oldldt);
>  		else
> -			kfree(oldldt);
> +			put_page(virt_to_page(oldldt));
>  	}
>  	return 0;
>  }
> @@ -117,7 +116,7 @@ void destroy_context(struct mm_struct *m
>  		if ((unsigned)mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE)
>  			vfree(mm->context.ldt);
>  		else
> -			kfree(mm->context.ldt);
> +			put_page(virt_to_page(mm->context.ldt));

why not free_page() with all those checks if it is correct virt address which it 
brings?

regards,
-- 
Jiri Slaby
Faculty of Informatics, Masaryk University
Suse Labs
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