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| Question about the paging https://forum.osdev.org/viewtopic.php?f=13&t=32886 |
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| Author: | CandyMan [ Mon Apr 23, 2018 8:10 am ] |
| Post subject: | Question about the paging |
Question about the paging. I map first (64+8)GB memory 1:1 Whether it is possible to mix 1GB pages and 4KB pages? How to map video memory from 0xA0000-0xAFFFF at 0x1101000000 (68G+16M)? Code: MaxMemV = 64+8 ;72GB
mov ebx,512*8*(1+1) push ebx mov ebx,1024*1024 ;CR3=1M mov [PML4],ebx lea eax,[ebx+4096] mov [PDP],eax pxor mm0,mm0 pop ecx shr ecx,3 @@: dec ecx movq [fs:ebx+ecx*8],mm0 jnz @B mov eax,[PML4] mov ebx,[PDP] mov edx,ebx or bl,7 mov [fs:eax+8*000],ebx mov eax,1024*1024*1024 movd mm1,eax mov eax,1187h movd mm0,eax ;Fill page tables xor ecx,ecx .1: movq [fs:edx+8*ecx],mm0 paddq mm0,mm1 inc ecx cmp ecx,MaxMemV jb .1 |
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| Author: | iansjack [ Mon Apr 23, 2018 8:52 am ] |
| Post subject: | Re: Question about the paging |
Yes, you can map 4K pages and 1G pages in the same page table (in IA-32e mode). But note that not all processors that support IA-32e mode support 1GB pages, so you really need to check first (and make alternative provision if necessary). Unless you are careful, 1GB page mapping can be wasteful of resources. I prefer to keep it simple and use just 4K pages; this is, IMO, a far more flexible option. You map a region of video memory in exactly the same way that you would map any other area of memory. |
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| Author: | CandyMan [ Mon Apr 23, 2018 10:21 am ] |
| Post subject: | Re: Question about the paging |
can you present mixing sample code? |
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| Author: | iansjack [ Mon Apr 23, 2018 11:11 am ] |
| Post subject: | Re: Question about the paging |
No. It's all clearly explained in the Intel manuals. |
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