Re: AMD IOMMU issue with hibernate on Asrock X600

[Johannes Stezenbach <js@sig21.net>]

Hi Vasant,

On Sat, Feb 21, 2026 at 08:01:16PM +0530, Vasant Hegde wrote:
> We have managed to reproduce the issue internally.
> 
> 
> On 2/5/2026 7:35 PM, Johannes Stezenbach wrote:
> > On Wed, Feb 04, 2026 at 04:16:51PM +0100, Johannes Stezenbach wrote:
> >>
> >> Side note: I wanted to check AMD documents at https://docs.amd.com/
> >> but the "Create Account" button doesn't work. :-(
> >> (And why do they require an account anyway, Intel and ARM don't...)
> > 
> > Eventually I could download the "AMD I/O Virtualization Technology
> > (IOMMU) Specification" document (link on https://uefi.org/acpi
> > is stale, BTW).
> 
> 
> Latest public spec -> https://docs.amd.com/v/u/en-US/48882_3.10_PUB

Yeah, found it already. I guess I used the wrong search terms,
trying to find docs for the 8700G. Later I also found the 
"AMD64 Architecture Programmer’s Manual Volume 2: System Programming"
which has info on the APIC/xAPIC/x2APIC.

> If you have cycles, Can you try below patch (untested patch we will test it
> internally next week)?

I tried it with 6.19.3, doesn't seem to work reliably, but the
results are mixed, sometimes seems to work, sometimes doesn't.
(Trying a mix of suspend and hibernate, and hibernate mutiple times.)

I met the familiar

[  301.963784][ T5153] i >= MMIO_STATUS_TIMEOUT
[  301.963786][ T5153] WARNING: drivers/iommu/amd/init.c:952 at amd_iommu_enable_interrupts+0x4c8/0x550, CPU#0: pm-hiber
nate/5153
...
[  302.304252][ T5153] Call Trace:                                                                                      [  302.312118][ T5153]  <TASK>
[  302.319113][ T5153]  amd_iommu_reenable+0x10/0x20
[  302.330910][ T5153]  lapic_resume+0x176/0x260

on hibernation entry (doesn't show up in dmesg, needs serial
console) and also on hibernation resume after image loading
(this shows up in dmesg).


Thanks,
Johannes


> <--
> commit fd6196203c8637951e56bf144015c020f57d5a34
> Author: Vasant Hegde <vasant.hegde@amd.com>
> Date:   Sat Feb 21 19:48:59 2026 +0530
> 
>     iommu/amd: Skip IOMMU re-initialization if already enabled during resume
> 
>     Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
> 
> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
> index 384c90b4f90a..eb5bff024f95 100644
> --- a/drivers/iommu/amd/init.c
> +++ b/drivers/iommu/amd/init.c
> @@ -3058,15 +3058,23 @@ static void disable_iommus(void)
>  static void amd_iommu_resume(void *data)
>  {
>  	struct amd_iommu *iommu;
> +	u64 ctrl;
> +	bool enable_intr = false;
> 
> -	for_each_iommu(iommu)
> +	for_each_iommu(iommu) {
> +		ctrl = readq(iommu->mmio_base + MMIO_CONTROL_OFFSET);
> +		if (ctrl & BIT_ULL(CONTROL_IOMMU_EN))
> +			continue;
> +
> +		enable_intr = true;
>  		iommu_apply_resume_quirks(iommu);
> 
> -	/* re-load the hardware */
> -	for_each_iommu(iommu)
> +		/* re-load the hardware */
>  		early_enable_iommu(iommu);
> +	}
> 
> -	amd_iommu_enable_interrupts();
> +	if (enable_intr)
> +		amd_iommu_enable_interrupts();
>  }
> 
>  static int amd_iommu_suspend(void *data)
> 
>