** Description changed:
The (supposedly unintended) re-enabling of GDS force migration in the
- 6.10 kernels causes the AVX instruction to be disabled on older CPUs
- which have no available microcode update. This causes various programs
- to crash due to the unconditional use of AVX in libgnutls.so, libxul.so,
- etc.
+ Ubuntu 6.10 kernels causes the AVX instruction to be disabled on older
+ CPUs which have no available microcode update. This causes various
+ programs to crash due to the unconditional use of AVX in libgnutls.so,
+ libxul.so, etc.
Typically "traps" of "invalid opcode" will be seen in dmesg output along
with the initial notice:
[ 0.121833] GDS: Microcode update needed! Disabling AVX as mitigation.
[ 0.121835] GDS: Mitigation: AVX disabled, no microcode
-
When GDS force mitigation appeared in the kernel, with default "y", it
created a lot of issues like these and Ubuntu quickly patched all their
kernels, this from the 6.2.0-28.29_6.2.0-31.31 diff:
+
+ ==========
```
diff -u linux-6.2.0/debian.master/changelog
linux-6.2.0/debian.master/changelog
--- linux-6.2.0/debian.master/changelog
+++ linux-6.2.0/debian.master/changelog
@@ -1,3 +1,13 @@
+linux (6.2.0-31.31) lunar; urgency=medium
+
+ * lunar/linux: 6.2.0-31.31 -proposed tracker (LP: #2031146)
+
+ * libgnutls report "trap invalid opcode" when trying to install packages
over
+ https (LP: #2031093)
+ - [Config]: disable CONFIG_GDS_FORCE_MITIGATION
+
+ -- Thadeu Lima de Souza Cascardo <casca...@canonical.com> Mon, 14 Aug 2023
08:29:52 -0300
+
linux (6.2.0-28.29) lunar; urgency=medium
* lunar/linux: 6.2.0-28.29 -proposed tracker (LP: #2030547)
diff -u linux-6.2.0/debian.master/config/annotations
linux-6.2.0/debian.master/config/annotations
--- linux-6.2.0/debian.master/config/annotations
+++ linux-6.2.0/debian.master/config/annotations
@@ -4992,7 +4992,7 @@
CONFIG_GCC_VERSION policy<{'amd64': '120200',
'arm64': '120200', 'armhf': '120200', 'ppc64el': '120200', 'riscv64': '120200',
's390x': '120200'}>
CONFIG_GCOV_KERNEL policy<{'amd64': 'n',
'arm64': 'n', 'armhf': 'n', 'ppc64el': 'n', 'riscv64': 'n', 's390x': 'n'}>
CONFIG_GDB_SCRIPTS policy<{'amd64': 'y',
'arm64': 'y', 'armhf': 'y', 'ppc64el': 'y', 'riscv64': 'y', 's390x': 'y'}>
-CONFIG_GDS_FORCE_MITIGATION policy<{'amd64': 'y'}>
+CONFIG_GDS_FORCE_MITIGATION policy<{'amd64': 'n'}>
CONFIG_GEMINI_ETHERNET policy<{'arm64': 'm',
'armhf': 'm', 'ppc64el': 'm', 'riscv64': 'm'}>
CONFIG_GENERIC_ADC_BATTERY policy<{'amd64': 'm',
'arm64': 'm', 'armhf': 'm', 'ppc64el': 'm', 'riscv64': 'm'}>
CONFIG_GENERIC_ADC_THERMAL policy<{'amd64': 'm',
'arm64': 'm', 'armhf': 'm', 'ppc64el': 'm', 'riscv64': 'm'}>
```
+ ==========
- In 6.10 the option was renamed from CONFIG_GDS_FORCE_MITIGATION but when
Ubuntu jumped from 6.8 to 6.10, this customization was lost, from the
6.8.0-31.31_6.10.0-15.15 diff:
+
+ In upstream 6.9 the option was renamed from CONFIG_GDS_FORCE_MITIGATION but
when Ubuntu jumped from 6.8 to 6.10, this customization was lost, from the
6.8.0-31.31_6.10.0-15.15 diff:
+
+ ==========
```
CONFIG_GDB_SCRIPTS policy<{'amd64': 'y',
'arm64': 'y', 'armhf': 'y', 'ppc64el': 'y', 'riscv64': 'y', 's390x': 'y'}>
-CONFIG_GDS_FORCE_MITIGATION policy<{'amd64': 'n'}>
CONFIG_GEMINI_ETHERNET policy<{'arm64': 'm',
'armhf': 'm', 'ppc64el': 'm', 'riscv64': 'm'}>
...
CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY policy<{'arm64': 'y'}>
+CONFIG_MITIGATION_CALL_DEPTH_TRACKING policy<{'amd64': 'y'}>
+CONFIG_MITIGATION_GDS_FORCE policy<{'amd64': 'y'}>
+CONFIG_MITIGATION_IBPB_ENTRY policy<{'amd64': 'y'}>
+CONFIG_MITIGATION_IBRS_ENTRY policy<{'amd64': 'y'}>
```
+ ==========
+
I am sure this was an oversight, and that the old option was simply
dropped because it didn't exist any longer, without thinking of it being
renamed (among a lot of other renames).
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https://bugs.launchpad.net/bugs/2077145
Title:
GDS force mitigation re-enabled in 6.10 causing crashes
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