linux-kernel - Re: AMD GPU driver load hitting BUG_ON in sync_global_pgds

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Message-ID: <35f08d6c-cc90-43fd-a24a-195b5d0e6d32@amd.com>
Date: Wed, 23 Apr 2025 12:10:32 +0530
From: Bharata B Rao <bharata@....com>
To: Balbir Singh <balbirs@...dia.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Cc: Dave Hansen <dave.hansen@...ux.intel.com>, luto@...nel.org,
 peterz@...radead.org, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 x86@...nel.org, hpa@...or.com, nikunj@....com, kees@...nel.org,
 alexander.deucher@....com
Subject: Re: AMD GPU driver load hitting BUG_ON in sync_global_pgds_l5()

On 22-Apr-25 12:44 PM, Balbir Singh wrote:
> On 4/22/25 16:34, Bharata B Rao wrote:
> 
> Could you please confirm if this is a new issue? Sounds like your hitting it on 6.8.12+?
> I've never tested this on a system with 5 levels of page tables, but with 5 levels you get
> 52 bits of VA and you'll need to look at the KASLR logic (max_pfn + padding) to see where
> your ranges are getting assigned.
> 
> I'd start by dumping the kaslr_regions array.

Here is how the ranges look like for the upstream kernel for two boots:

Iteration 1:
kaslr_region: base[0] ff4552df80000000 size_tb 1000
kaslr_region: end[0] fffffffffffff
kaslr_region: base[1] ff69c69640000000 size_tb 3200
kaslr_region: base[2] ffd3140680000000 size_tb 40

Iteration 2:
kaslr_region: base[0] ff3a9c84c0000000 size_tb 1000
kaslr_region: end[0] fffffffffffff
kaslr_region: base[1] ff73d27480000000 size_tb 3200
kaslr_region: base[2] fff01edb40000000 size_tb 40

Regards,
Bharata.