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

["Nakajima, Jun" <jun.nakajima@xxxxxxxxx>]

Keir Fraser wrote:
> 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).

One more thing, NX/XD support. The bit 63 really confuses Xen and has
impacts on pfn calculation routines/macros. I needed to disable that
feature on x86-64 xenolinux at this point.

Jun

> 
>   -- Keir



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