Re: [PATCH 4/21] i386 Broken bios common

[Ingo Molnar]

* Zachary Amsden <zach@xxxxxxxxxx> wrote:

> >>-	gdt[0x40 / 8] = bad_bios_desc;
> >>+	gdt[0x40 / 8] = gdt[GDT_ENTRY_BAD_BIOS_CACHE];
> >
> >i like the cleanup, but wouldnt it be simpler to dedicate GDT entry #8 
> >to the 0x40 descriptor, and hence be compatible with such broken BIOSes 
> >by default? Right now entry #8 is taken up by TLS segment #2, but we 
> >could change GDT_ENTRY_TLS_MIN from 6 to 9 and push the TLS segments to 
> >entries 9,10,11. [ Could there be any buggy SMM code that relies on 
> >having something at 0x40? ]
> 
> I worry that there could be buggy userspace code that relies on having 
> selector 0x40 - notably Wine.  So although I would like to make 0x40 
> the default, can't be guaranteed.

why use up a GDT entry then for GDT_ENTRY_BAD_BIOS_CACHE? Just put it 
into a global variable, into the readmostly section.

	Ingo
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