Commit efe31382 authored by David Kaplan's avatar David Kaplan Committed by Borislav Petkov (AMD)
Browse files

x86/bugs: Restructure BHI mitigation 



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: default avatarDavid Kaplan <david.kaplan@amd.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/20250418161721.1855190-13-david.kaplan@amd.com
parent ddfca943

arch/x86/kernel/cpu/bugs.c

+27 −4
Original line number Diff line number Diff line
@@ -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]);