Messages in this thread | | | Subject | Re: [PATCH 0/5] iommu/amd: fixes for suspend/resume | From | Maxim Levitsky <> | Date | Thu, 02 Dec 2021 01:08:01 +0200 |
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On Tue, 2021-11-23 at 18:10 +0200, Maxim Levitsky wrote: > As I sadly found out, a s3 cycle makes the AMD's iommu stop sending interrupts > until the system is rebooted. > > I only noticed it now because otherwise the IOMMU works, and these interrupts > are only used for errors and for GA log which I tend not to use by > making my VMs do mwait/pause/etc in guest (cpu-pm=on). > > There are two issues here that prevent interrupts from being generated after > s3 cycle: > > 1. GA log base address was not restored after resume, and was all zeroed > after resume (by BIOS or such). > > In theory if BIOS writes some junk to it, that can even cause a memory corruption. > Patch 2 fixes that. > > 2. INTX (aka x2apic mode) settings were not restored after resume. > That mode is used regardless if the host uses/supports x2apic, but rather when > the IOMMU supports it, and mine does. > Patches 3-4 fix that. > > Note that there is still one slight (userspace) bug remaining: > During suspend all but the boot CPU are offlined and then after resume > are onlined again. > > The offlining moves all non-affinity managed interrupts to CPU0, and > later when all other CPUs are onlined, there is nothing in the kernel > to spread back the interrupts over the cores. > > The userspace 'irqbalance' daemon does fix this but it seems to ignore > the IOMMU interrupts in INTX mode since they are not attached to any > PCI device, and thus they remain on CPU0 after a s3 cycle, > which is suboptimal when the system has multiple IOMMUs > (mine has 4 of them). > > Setting the IRQ affinity manually via /proc/irq/ does work. > > This was tested on my 3970X with both INTX and regular MSI mode (later was enabled > by patching out INTX detection), by running a guest with AVIC enabled and with > a PCI assigned device (network card), and observing interrupts from > IOMMU while guest is mostly idle. > > This was also tested on my AMD laptop with 4650U (which has the same issue) > (I tested only INTX mode) > > Patch 1 is a small refactoring to remove an unused struct field. > > Best regards, > Maxim Levitsky > > Maxim Levitsky (5): > iommu/amd: restore GA log/tail pointer on host resume > iommu/amd: x2apic mode: re-enable after resume > iommu/amd: x2apic mode: setup the INTX registers on mask/unmask > iommu/amd: x2apic mode: mask/unmask interrupts on suspend/resume > iommu/amd: remove useless irq affinity notifier > > drivers/iommu/amd/amd_iommu_types.h | 2 - > drivers/iommu/amd/init.c | 107 +++++++++++++++------------- > 2 files changed, 58 insertions(+), 51 deletions(-) > > -- > 2.26.3 > >
Polite ping on these patches. Best regards, Maxim Levitsky
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