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| author | Thomas Gleixner <tglx@linutronix.de> | 2023-10-02 13:59:56 +0200 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2023-10-24 15:05:54 +0200 |
| commit | 634ac23ad609b3ddd9e0e478bd5afbf49d3a2556 (patch) | |
| tree | b67c0fab5a46a5fa3f0dd9a7a37aa4f105ca026d /arch/x86/Kconfig | |
| parent | x86/microcode: Clean up mc_cpu_down_prep() (diff) | |
| download | linux-634ac23ad609b3ddd9e0e478bd5afbf49d3a2556.tar.xz linux-634ac23ad609b3ddd9e0e478bd5afbf49d3a2556.zip | |
x86/microcode: Handle "nosmt" correctly
On CPUs where microcode loading is not NMI-safe the SMT siblings which
are parked in one of the play_dead() variants still react to NMIs.
So if an NMI hits while the primary thread updates the microcode the
resulting behaviour is undefined. The default play_dead() implementation on
modern CPUs is using MWAIT which is not guaranteed to be safe against
a microcode update which affects MWAIT.
Take the cpus_booted_once_mask into account to detect this case and
refuse to load late if the vendor specific driver does not advertise
that late loading is NMI safe.
AMD stated that this is safe, so mark the AMD driver accordingly.
This requirement will be partially lifted in later changes.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231002115903.087472735@linutronix.de
Diffstat (limited to 'arch/x86/Kconfig')
| -rw-r--r-- | arch/x86/Kconfig | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 011cb7f200d9..db7512008ff7 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1320,7 +1320,7 @@ config MICROCODE_INITRD32 config MICROCODE_LATE_LOADING bool "Late microcode loading (DANGEROUS)" default n - depends on MICROCODE + depends on MICROCODE && SMP help Loading microcode late, when the system is up and executing instructions is a tricky business and should be avoided if possible. Just the sequence |