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Re: [Qemu-stable] [Qemu-devel] [PATCH] fix guest physical bits to match


From: Paolo Bonzini
Subject: Re: [Qemu-stable] [Qemu-devel] [PATCH] fix guest physical bits to match host, to go beyond 1TB guests
Date: Tue, 16 Jul 2013 21:24:30 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7

Il 16/07/2013 20:11, Eduardo Habkost ha scritto:
> For physical bit size, what about extending it in a backwards-compatible
> way? Something like this:
> 
>     *eax = 0x0003000; /* 48 bits virtual */
>     if (ram_size < 1TB) {
>         physical_size = 40; /* Keeping backwards compatibility */
>     } else if (ram_size < 4TB) {
>         physical_size = 42;

Why not go straight up to 44?

>     } else {
>         abort();
>     }
>     if (supported_host_physical_size() < physical_size) {
>         abort();
>     }
>     *eax |= physical_size;
> 
> (Of course, the abort() calls should be replaced with proper error
> reporting)

This makes sense too.  Though the best would be of course to use CPUID
values coming from the real processors, and only using 40 for backwards
compatibility.

Paolo



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