Re: [Xen-devel] xen and cr0,cr3,cr4

[Adam Sulmicki <adam@xxxxxxxxxxxx>]

On Sun, 28 Nov 2004, Ian Pratt wrote:

> Nope, that's the initial page table when the machine boots.
>
> Even if it were possible from ring 1, reading cr3 directly
> wouldn't necessary give you want you want e.g. if you 're in one
> of the shadow page table modes.
>
> The easiest way to get the base within Linux is current->mm->pgd
> (modulo lazy switching).

I must be missing something obvious.

Using 4MB pages, under xenolinux, when I try to print the Page Directory I
Get output like this.

PD 0x020-0x020[0x04965067]V:0128M-0132M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x100-0x100[0x04191067]V:1024M-1028M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x2FF-0x2FF[0x04b54067]V:3068M-3072M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x300-0x30F[0x02c0f067]V:3072M-3136M-1>P:++++M-++++M-1 S:0064MB F:PK
PD 0x312-0x312[0x06b00067]V:3144M-3148M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x3EF-0x3EF[0x02c10067]V:4028M-4032M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x3F0-0x3F0[0x00c001e1]V:4032M-4036M-1>P:0012M-0016M-1 S:0004MB F:PM
PD 0x3F1-0x3FA[0x024001e3]V:4036M-4076M-1>P:0000M-0040M-1 S:0040MB F:PM
PD 0x3FB-0x3FB[0x040cf063]V:4076M-4080M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x3FD-0x3FD[0x001ef063]V:4084M-4088M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x3FE-0x3FF[0x0017d063]V:4088M-4096M-1>P:++++M-++++M-1 S:0008MB F:PK

This _seems_ mostly correct since those 4032M-4036 and 4036M-4076
(repeated below) seem to match original setup from x86_32.S

PD 0x3F0-0x3F0[0x00c001e1]V:4032M-4036M-1>P:0012M-0016M-1 S:0004MB F:PM
PD 0x3F1-0x3FA[0x024001e3]V:4036M-4076M-1>P:0000M-0040M-1 S:0040MB F:PM

I can also repeat the said output using 4kb pages setup.

PD 0x020-0x020[0x03a12067]V:0128M-0132M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x100-0x100[0x03a13067]V:1024M-1028M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x2FF-0x2FF[0x03a11067]V:3068M-3072M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x300-0x30F[0x02c0f067]V:3072M-3136M-1>P:++++M-++++M-1 S:0064MB F:PK
PD 0x312-0x312[0x03cfc067]V:3144M-3148M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x3EF-0x3EF[0x02c10067]V:4028M-4032M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x3F0-0x3F0[0x004f9021]V:4032M-4036M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x3F1-0x3FA[0x004ff023]V:4036M-4076M-1>P:++++M-++++M-1 S:0040MB F:PK
PD 0x3FB-0x3FB[0x05540063]V:4076M-4080M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x3FD-0x3FD[0x005ed063]V:4084M-4088M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x3FE-0x3FF[0x0057f063]V:4088M-4096M-1>P:++++M-++++M-1 S:0008MB F:PK

once again I get 4032M-4036 and 4036M-4076, and the "PK" instead of "PM"
indicates that it is using 4kb pages instead of 4mb pages.

PD 0x3F0-0x3F0[0x004f9021]V:4032M-4036M-1>P:++++M-++++M-1 S:0004MB F:PK
PD 0x3F1-0x3FA[0x004ff023]V:4036M-4076M-1>P:++++M-++++M-1 S:0040MB F:PK

All dandy and nice. now the weird part is that if I try to list Page Table
entries referenced by by Page Directory in either setup I get an ooops
saying that the referneced Page Table is not in memory.

No such problems in linux classic... weird.




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