2024-04-09 17:51:44

by Sean Christopherson

Subject: [PATCH 2/3] x86/cpu: Disable BHI mitigation by default when SPECULATION_MITIGATIONS=n

Rework the initialization of bhi_mitigation to use positive CONFIG tests
for the ON/AUTO cases so that lack of *any* CONFIG_SPECTRE_BHI_* #define,
i.e. when the kernel is built with CONFIG_SPECULATION_MITIGATIONS=n,
results in the mitigation being OFF by default, not AUTO.

Per the help text for SPECULATION_MITIGATIONS, the intent is that 'N'
disables all mitigations.

Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob")
Cc: [email protected]
Cc: Pawan Gupta <[email protected]>
Cc: Daniel Sneddon <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
---
arch/x86/kernel/cpu/bugs.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 295463707e68..e1775debeafe 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1630,9 +1630,9 @@ enum bhi_mitigations {
};

static enum bhi_mitigations bhi_mitigation __ro_after_init =
- IS_ENABLED(CONFIG_SPECTRE_BHI_ON) ? BHI_MITIGATION_ON :
- IS_ENABLED(CONFIG_SPECTRE_BHI_OFF) ? BHI_MITIGATION_OFF :
- BHI_MITIGATION_AUTO;
+ IS_ENABLED(CONFIG_SPECTRE_BHI_ON) ? BHI_MITIGATION_ON :
+ IS_ENABLED(CONFIG_SPECTRE_BHI_AUTO) ? BHI_MITIGATION_AUTO :
+ BHI_MITIGATION_OFF;

static int __init spectre_bhi_parse_cmdline(char *str)
{
--
2.44.0.478.gd926399ef9-goog

2024-04-10 14:31:34

by tip-bot2 for Linus Torvalds

Subject: [tip: x86/urgent] x86/cpu: Disable BHI mitigation by default when SPECULATION_MITIGATIONS=n

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: e8f2ec1cc10e86adfc2089fb93a1158e69989bbd
Gitweb: https://git.kernel.org/tip/e8f2ec1cc10e86adfc2089fb93a1158e69989bbd
Author: Sean Christopherson <[email protected]>
AuthorDate: Tue, 09 Apr 2024 10:51:06 -07:00
Committer: Ingo Molnar <[email protected]>
CommitterDate: Wed, 10 Apr 2024 16:22:56 +02:00

x86/cpu: Disable BHI mitigation by default when SPECULATION_MITIGATIONS=n

Rework the initialization of bhi_mitigation to use positive CONFIG tests
for the ON/AUTO cases so that lack of *any* CONFIG_SPECTRE_BHI_* #define,
i.e. when the kernel is built with CONFIG_SPECULATION_MITIGATIONS=n,
results in the mitigation being OFF by default, not AUTO.

Per the help text for SPECULATION_MITIGATIONS, the intent is that 'N'
disables all mitigations.

Fixes: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob")
Signed-off-by: Sean Christopherson <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Reviewed-by: Daniel Sneddon <[email protected]>
Cc: [email protected]
Cc: Linus Torvalds <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
arch/x86/kernel/cpu/bugs.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 27f5004..7e4a706 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1630,9 +1630,9 @@ enum bhi_mitigations {
};

static enum bhi_mitigations bhi_mitigation __ro_after_init =
- IS_ENABLED(CONFIG_SPECTRE_BHI_ON) ? BHI_MITIGATION_ON :
- IS_ENABLED(CONFIG_SPECTRE_BHI_OFF) ? BHI_MITIGATION_OFF :
- BHI_MITIGATION_AUTO;
+ IS_ENABLED(CONFIG_SPECTRE_BHI_ON) ? BHI_MITIGATION_ON :
+ IS_ENABLED(CONFIG_SPECTRE_BHI_AUTO) ? BHI_MITIGATION_AUTO :
+ BHI_MITIGATION_OFF;

static int __init spectre_bhi_parse_cmdline(char *str)
{