Re: [Xen-devel] [patch] PAE support revisited

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 23 Mar 2005, at 15:22, Nakajima, Jun wrote:

> I like the idea of new macros. The other thing is that the current
> shadow code has issues with supporting 32-bit unmodified guests on
> x86_64 (e.g. VMX domain). For example, the following does not work, and
> we need new definitions (e.g. l1_pgentry_32_t) for that purpose.
>   typedef struct { unsigned long l1_lo; } l1_pgentry_t;
>   typedef struct { unsigned long l2_lo; } l2_pgentry_t;
> The linear page table does not work either, because the page table
> entries are different (i.e. 4-byte vs. 8-byte). I think we need to get
> the current shadow code working for 2-level page tables on both x86 and
> x86_64 first, then extend it to support 3/4-level page tables, probably
> in a sperate file?
I suspect there may be a lot of commonality between the code for 
handling different pagteable arrangements (2 vs. 3 vs 4 level, and 
4-byte vs 8-byte PTEs). Rather than duping the code for each case, 
maybe we can have one codebase with minimal ifdef's that works with the 
l_pgentry types, then perhaps gets compiled multiple times with 
different-size types and macros differently defined?
As you say, it's probably best to consider the best course of action 
after we have x-type guest working on x-type host (for x == 
x86/32,PAE,x86/64).
 -- Keir




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