Commit 9f536487 authored Jan 11, 2023 by James Morse Committed by Yongqiang Liu Jan 11, 2023

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

stable inclusion
from stable-v4.19.268
commit 51febca41ae0333c29b4b12778f045a705d89370
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I69KBO


CVE: NA

--------------------------------

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: c20d55174479 ("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>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>

parent 62fb1cde

arch/arm64/kernel/cpu_errata.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -1306,6 +1306,12 @@ 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: