lisa/android_kernel_xiaomi_sm8350
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

arm64: errata: Fix KVM Spectre-v2 mitigation selection for Cortex-A57/A72

Browse Source 
Both the Spectre-v2 and Spectre-BHB mitigations involve running a sequence
immediately after exiting a guest, before any branches. In the stable
kernels these sequences are built by copying templates into an empty vector
slot.

For Spectre-BHB, Cortex-A57 and A72 require the branchy loop with k=8.
If Spectre-v2 needs mitigating at the same time, a firmware call to EL3 is
needed. The work EL3 does at this point is also enough to mitigate
Spectre-BHB.

When enabling the Spectre-BHB mitigation, spectre_bhb_enable_mitigation()
should check if a slot has already been allocated for Spectre-v2, meaning
no work is needed for Spectre-BHB.

This check was missed in the earlier backport, add it.

Fixes: 9013fd4bc9 ("arm64: Mitigate spectre style branch history side channels")
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
James Morse 2022-11-30 18:28:19 +00:00 committed by Greg Kroah-Hartman
parent 44ccd8c52f
commit c9ecc42094
1 changed files with 7 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/arm64/kernel/cpu_errata.c
View File

@ -1363,6 +1363,12 @@ void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry)
} else if (spectre_bhb_loop_affected(SCOPE_LOCAL_CPU)) {
switch (spectre_bhb_loop_affected(SCOPE_SYSTEM)) {
case 8:
/*
* A57/A72-r0 will already have selected the
* spectre-indirect vector, which is sufficient
* for BHB too.
*/
if (!__this_cpu_read(bp_hardening_data.fn))
kvm_setup_bhb_slot(__spectre_bhb_loop_k8_start);
break;
case 24: