Re: PAT 64b: Basic PAT implementation
- From: "Daniel J Blueman" <daniel.blueman@xxxxxxxxx>
- Date: Mon, 17 Dec 2007 10:40:33 +0000
On 14 Dec, 00:50, Andi Kleen <a...@xxxxxx> wrote:
+void __cpuinit pat_init(void)
+{
+ /* Set PWT+PCD to Write-Combining. All other bits stay the same */
+ if (cpu_has_pat) {
All the old CPUs (PPro etc.) with known PAT bugs need to clear this flag
now in their CPU init functions. It is fine to be aggressive there
because these old systems have lived so long without PAT they can do
so forever. So perhaps it's best to just white list it only for newer
CPUs on the Intel side at least.
Another problem is that there are some popular modules (ATI, Nvidia for once)
who reprogram the PAT registers on their own, likely different. Need some way to detect
that case I guess, otherwise lots of users will see strange malfunctions.
Maybe recheck after module load?
This may not be as big problem as thought, since sane and at least one
vendor driver (Quadrics QsNetII) searches the PAT slots for a WC entry
- where this has already been setup by the kernel, it'll use the right
one.
--+ |||
+ 000 WB default
+ 010 UC_MINUS _PAGE_PCD
+ 011 WC _PAGE_WC
+ PAT bit unused */
+ pat = PAT(0,WB) | PAT(1,WT) | PAT(2,UC_MINUS) | PAT(3,WC) |
+ PAT(4,WB) | PAT(5,WT) | PAT(6,UC_MINUS) | PAT(7,WC);
+ rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
+ wrmsrl(MSR_IA32_CR_PAT, pat);
+ __flush_tlb_all();
+ asm volatile("wbinvd");
Have you double checked this is the full procedure from the manual? iirc there
were some steps missing.
-Andi
Daniel J Blueman
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
- Prev by Date: Re: [PATCH 3/3] net: wireless: bcm43xx: big_buffer_sem semaphore to mutex
- Next by Date: Re: [RFC] move free page back to MIGRATE_MOVABLE?
- Previous by thread: INITIO scsi driver fails to work properly
- Next by thread: Re: CMD646 & cdrom: drive appears confused & drive not ready for command
- Index(es):
Relevant Pages
|
