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x86/bugs: Restructure BHI mitigation

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Restructure BHI mitigation to use select/update/apply functions to create
consistent vulnerability handling.  BHI mitigation was previously selected
from within spectre_v2_select_mitigation() and now is selected from
cpu_select_mitigation() like with all others.

Define new AUTO mitigation for BHI.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/20250418161721.1855190-13-david.kaplan@amd.com
This commit is contained in:
David Kaplan 2025-04-18 11:17:17 -05:00 committed by Borislav Petkov (AMD)
parent ddfca9430a
commit efe313827c
1 changed files with 27 additions and 4 deletions
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31
arch/x86/kernel/cpu/bugs.c
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@ -82,6 +82,9 @@ static void __init l1d_flush_select_mitigation(void);
static void __init srso_select_mitigation(void);
static void __init gds_select_mitigation(void);
static void __init gds_apply_mitigation(void);
static void __init bhi_select_mitigation(void);
static void __init bhi_update_mitigation(void);
static void __init bhi_apply_mitigation(void);
/* The base value of the SPEC_CTRL MSR without task-specific bits set */
u64 x86_spec_ctrl_base;
@ -208,6 +211,7 @@ void __init cpu_select_mitigations(void)
*/
srso_select_mitigation();
gds_select_mitigation();
bhi_select_mitigation();
/*
* After mitigations are selected, some may need to update their
@ -225,6 +229,7 @@ void __init cpu_select_mitigations(void)
taa_update_mitigation();
mmio_update_mitigation();
rfds_update_mitigation();
bhi_update_mitigation();
spectre_v1_apply_mitigation();
retbleed_apply_mitigation();
@ -235,6 +240,7 @@ void __init cpu_select_mitigations(void)
rfds_apply_mitigation();
srbds_apply_mitigation();
gds_apply_mitigation();
bhi_apply_mitigation();
}
/*
@ -1794,12 +1800,13 @@ static bool __init spec_ctrl_bhi_dis(void)
enum bhi_mitigations {
BHI_MITIGATION_OFF,
BHI_MITIGATION_AUTO,
BHI_MITIGATION_ON,
BHI_MITIGATION_VMEXIT_ONLY,
};
static enum bhi_mitigations bhi_mitigation __ro_after_init =
IS_ENABLED(CONFIG_MITIGATION_SPECTRE_BHI) ? BHI_MITIGATION_ON : BHI_MITIGATION_OFF;
IS_ENABLED(CONFIG_MITIGATION_SPECTRE_BHI) ? BHI_MITIGATION_AUTO : BHI_MITIGATION_OFF;
static int __init spectre_bhi_parse_cmdline(char *str)
{
@ -1820,6 +1827,25 @@ static int __init spectre_bhi_parse_cmdline(char *str)
early_param("spectre_bhi", spectre_bhi_parse_cmdline);
static void __init bhi_select_mitigation(void)
{
if (!boot_cpu_has(X86_BUG_BHI) || cpu_mitigations_off())
bhi_mitigation = BHI_MITIGATION_OFF;
if (bhi_mitigation == BHI_MITIGATION_AUTO)
bhi_mitigation = BHI_MITIGATION_ON;
}
static void __init bhi_update_mitigation(void)
{
if (spectre_v2_cmd == SPECTRE_V2_CMD_NONE)
bhi_mitigation = BHI_MITIGATION_OFF;
if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) &&
spectre_v2_cmd == SPECTRE_V2_CMD_AUTO)
bhi_mitigation = BHI_MITIGATION_OFF;
}
static void __init bhi_apply_mitigation(void)
{
if (bhi_mitigation == BHI_MITIGATION_OFF)
return;
@ -1961,9 +1987,6 @@ static void __init spectre_v2_select_mitigation(void)
mode == SPECTRE_V2_RETPOLINE)
spec_ctrl_disable_kernel_rrsba();
if (boot_cpu_has(X86_BUG_BHI))
bhi_select_mitigation();
spectre_v2_enabled = mode;
pr_info("%s\n", spectre_v2_strings[mode]);