linux-kernel - Re: Interrupts enabled after amd_iommu

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Date:   Mon, 04 Jan 2021 23:39:41 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Borislav Petkov <bp@...en8.de>, iommu@...ts.linux-foundation.org
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: Re: Interrupts enabled after amd_iommu_resume+0x0/0x40

On Tue, 2021-01-05 at 00:23 +0100, Borislav Petkov wrote:
> On Mon, Jan 04, 2021 at 02:22:50PM +0100, Borislav Petkov wrote:
> > Hi folks,
> > 
> > syscore_resume() doesn't like when the AMD iommu driver enables
> > interrupts in its ->resume hook when I resume the box from suspend to
> > RAM.
> > 
> > All kinds of warnings get triggered too:
> > 
> > [   17.386830] WARNING: CPU: 0 PID: 2 at kernel/time/timekeeping.c:824 ktime_get+0x8d/0xa0
> > [   17.386830] WARNING: CPU: 0 PID: 2 at kernel/time/timekeeping.c:867 ktime_get_with_offset+0xda/0xf0
> > [   17.386830] WARNING: CPU: 0 PID: 2 at kernel/time/timekeeping.c:824 ktime_get+0x8d/0xa0
> > [   17.386830] WARNING: CPU: 0 PID: 2 at kernel/time/timekeeping.c:867 ktime_get_with_offset+0xda/0xf0
> > [   17.386830] WARNING: CPU: 0 PID: 1576 at drivers/base/syscore.c:103 syscore_resume+0x12d/0x160
> > 
> > but when I comment out the
> > 
> >        amd_iommu_enable_interrupts()
> > 
> > call in the resume hook, all is fine and quiet and box resumes.
> > 
> > I'll try to bisect later to try to pinpoint it better because I don't
> > see what recent change would've caused this. But someone might have a
> > better idea so CC the usual suspects.
> 
> Ok, bisected to:
> 
> # first bad commit: [d1adcfbb520c43c10fc22fcdccdd4204e014fb53] iommu/amd: Fix IOMMU interrupt generation in X2APIC mode
> 
> That patch reverts cleanly ontop of -rc2 and with it reverted, the
> machine resumes fine.

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index f54cd79b43e4..6a1f7048dacc 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -1973,8 +1973,6 @@ static int iommu_setup_msi(struct amd_iommu *iommu)
 		return r;
 	}
 
-	iommu->int_enabled = true;
-
 	return 0;
 }
 
@@ -2169,6 +2167,7 @@ static int iommu_init_irq(struct amd_iommu *iommu)
 	if (ret)
 		return ret;
 
+	iommu->int_enabled = true;
 enable_faults:
 	iommu_feature_enable(iommu, CONTROL_EVT_INT_EN);
 


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