Ok, turns out it's not a version issue but a config issue:
CONFIG_INTEL_IOMMU_DEFAULT_ON=y is what causes the problem. The reason
that 6.6.18 from the mainline ppa is good while 6.6.19 is bad is that
the former has this disabled while the later has it enabled:
% diff -u0 /boot/config-6.6.1*-generic
--- /boot/config-6.6.18-060618-generic 2024-02-23 10:34:17.000000000 +0100
+++ /boot/config-6.6.19-060619-generic 2024-03-01 14:53:56.000000000 +0100
@@ -3 +3 @@
-# Linux/x86 6.6.18 Kernel Configuration
+# Linux/x86 6.6.19 Kernel Configuration
@@ -5 +5 @@
-CONFIG_CC_VERSION_TEXT="x86_64-linux-gnu-gcc-13 (Ubuntu 13.2.0-23ubuntu4)
13.2.0"
+CONFIG_CC_VERSION_TEXT="x86_64-linux-gnu-gcc-13 (Ubuntu 13.2.0-16ubuntu1)
13.2.0"
@@ -14 +13,0 @@
-CONFIG_RUST_IS_AVAILABLE=y
@@ -9781 +9780 @@
-# CONFIG_INTEL_IOMMU_DEFAULT_ON is not set
+CONFIG_INTEL_IOMMU_DEFAULT_ON=y
@@ -9783 +9782 @@
-# CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON is not set
+CONFIG_INTEL_IOMMU_SCALABLE_MODE_DEFAULT_ON=y
Indeed, by just enabling CONFIG_INTEL_IOMMU_DEFAULT_ON in 6.6.18 it
becomes bad, while just disabling it in 6.6.19 makes it good.
Going back to the kernels shipped by Ubuntu where I originally observed the
problem, indeed that option is disabled in 6.5 (which works for me) and enabled
in 6.8 (which doesn't work for me):
% grep CONFIG_INTEL_IOMMU_DEFAULT_ON /boot/config-6.[58]*
/boot/config-6.5.0-45-generic:# CONFIG_INTEL_IOMMU_DEFAULT_ON is not set
/boot/config-6.8.0-48-generic:CONFIG_INTEL_IOMMU_DEFAULT_ON=y
Please let me know if there's further information I can provide that
could help resolve this issue.
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https://bugs.launchpad.net/bugs/2080693
Title:
Not resuming from suspend - Thinkpad E460
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