Re: [PATCH] Fix wrong message when RFI Flush is disable
From: Michal Suchánek <hidden>
Date: 2019-11-14 09:31:43
Also in:
lkml, stable
On Thu, Nov 14, 2019 at 08:07:35PM +1100, Michael Ellerman wrote:
On Thu, 2019-05-02 at 21:09:07 UTC, Gustavo Walbon wrote:quoted
From: "Gustavo L. F. Walbon" <redacted> The issue was showing "Mitigation" message via sysfs whatever the state of "RFI Flush", but it should show "Vulnerable" when it is disabled. If you have "L1D private" feature enabled and not "RFI Flush" you are vulnerable to meltdown attacks. "RFI Flush" is the key feature to mitigate the meltdown whatever the "L1D private" state. SEC_FTR_L1D_THREAD_PRIV is a feature for Power9 only. So the message should be as the truth table shows. CPU | L1D private | RFI Flush | sysfs | ----| ----------- | --------- | ------------------------------------- | P9 | False | False | Vulnerable P9 | False | True | Mitigation: RFI Flush P9 | True | False | Vulnerable: L1D private per thread P9 | True | True | Mitigation: RFI Flush, L1D private per | | | thread P8 | False | False | Vulnerable P8 | False | True | Mitigation: RFI Flush Output before this fix: # cat /sys/devices/system/cpu/vulnerabilities/meltdown Mitigation: RFI Flush, L1D private per thread # echo 0 > /sys/kernel/debug/powerpc/rfi_flush # cat /sys/devices/system/cpu/vulnerabilities/meltdown Mitigation: L1D private per thread Output after fix: # cat /sys/devices/system/cpu/vulnerabilities/meltdown Mitigation: RFI Flush, L1D private per thread # echo 0 > /sys/kernel/debug/powerpc/rfi_flush # cat /sys/devices/system/cpu/vulnerabilities/meltdown Vulnerable: L1D private per thread Link: https://github.com/linuxppc/issues/issues/243 Signed-off-by: Gustavo L. F. Walbon <redacted> Signed-off-by: Mauro S. M. Rodrigues <redacted>Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/4e706af3cd8e1d0503c25332b30cad33c97ed442 cheers
Fixes: ff348355e9c7 ("powerpc/64s: Enhance the information in
cpu_show_meltdown()")
Thanks
Michal