Commit bdd7fce7 authored by David Kaplan's avatar David Kaplan Committed by Borislav Petkov (AMD)
Browse files

x86/bugs: Restructure TAA mitigation 



Restructure TAA mitigation to use select/update/apply functions to
create consistent vulnerability handling.

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/20250418161721.1855190-3-david.kaplan@amd.com
parent 559c758b

arch/x86/kernel/cpu/bugs.c

+59 −35
Original line number Diff line number Diff line
@@ -65,6 +65,8 @@ static void __init mds_apply_mitigation(void); 
static void __init md_clear_update_mitigation(void);

static void __init md_clear_select_mitigation(void);

static void __init taa_select_mitigation(void);

static void __init taa_update_mitigation(void);

static void __init taa_apply_mitigation(void);

static void __init mmio_select_mitigation(void);

static void __init srbds_select_mitigation(void);

static void __init l1d_flush_select_mitigation(void);
@@ -194,6 +196,7 @@ void __init cpu_select_mitigations(void) 
	ssb_select_mitigation();

	l1tf_select_mitigation();

	mds_select_mitigation();

	taa_select_mitigation();

	md_clear_select_mitigation();

	srbds_select_mitigation();

	l1d_flush_select_mitigation();
@@ -210,8 +213,10 @@ void __init cpu_select_mitigations(void) 
	 * choices.

	 */

	mds_update_mitigation();

	taa_update_mitigation();



	mds_apply_mitigation();

	taa_apply_mitigation();

}



/*
@@ -397,6 +402,11 @@ static const char * const taa_strings[] = { 
	[TAA_MITIGATION_TSX_DISABLED]	= "Mitigation: TSX disabled",

};



static bool __init taa_vulnerable(void)

{

	return boot_cpu_has_bug(X86_BUG_TAA) && boot_cpu_has(X86_FEATURE_RTM);

}



static void __init taa_select_mitigation(void)

{

	if (!boot_cpu_has_bug(X86_BUG_TAA)) {
@@ -410,22 +420,28 @@ static void __init taa_select_mitigation(void) 
		return;

	}



	if (cpu_mitigations_off()) {

	if (cpu_mitigations_off())

		taa_mitigation = TAA_MITIGATION_OFF;

		return;



	/* Microcode will be checked in taa_update_mitigation(). */

	if (taa_mitigation == TAA_MITIGATION_AUTO)

		taa_mitigation = TAA_MITIGATION_VERW;



	if (taa_mitigation != TAA_MITIGATION_OFF)

		verw_clear_cpu_buf_mitigation_selected = true;

}



	/*

	 * TAA mitigation via VERW is turned off if both

	 * tsx_async_abort=off and mds=off are specified.

	 */

	if (taa_mitigation == TAA_MITIGATION_OFF &&

	    mds_mitigation == MDS_MITIGATION_OFF)

static void __init taa_update_mitigation(void)

{

	if (!taa_vulnerable() || cpu_mitigations_off())

		return;



	if (boot_cpu_has(X86_FEATURE_MD_CLEAR))

	if (verw_clear_cpu_buf_mitigation_selected)

		taa_mitigation = TAA_MITIGATION_VERW;

	else



	if (taa_mitigation == TAA_MITIGATION_VERW) {

		/* Check if the requisite ucode is available. */

		if (!boot_cpu_has(X86_FEATURE_MD_CLEAR))

			taa_mitigation = TAA_MITIGATION_UCODE_NEEDED;



		/*
@@ -440,7 +456,15 @@ static void __init taa_select_mitigation(void) 
		if ((x86_arch_cap_msr & ARCH_CAP_MDS_NO) &&

		   !(x86_arch_cap_msr & ARCH_CAP_TSX_CTRL_MSR))

			taa_mitigation = TAA_MITIGATION_UCODE_NEEDED;

	}



	pr_info("%s\n", taa_strings[taa_mitigation]);

}



static void __init taa_apply_mitigation(void)

{

	if (taa_mitigation == TAA_MITIGATION_VERW ||

	    taa_mitigation == TAA_MITIGATION_UCODE_NEEDED) {

		/*

		 * TSX is enabled, select alternate mitigation for TAA which is

		 * the same as MDS. Enable MDS static branch to clear CPU buffers.
@@ -453,6 +477,7 @@ static void __init taa_select_mitigation(void) 
		if (taa_nosmt || cpu_mitigations_auto_nosmt())

			cpu_smt_disable(false);

	}

}



static int __init tsx_async_abort_parse_cmdline(char *str)

{
@@ -660,7 +685,6 @@ static void __init md_clear_update_mitigation(void) 


static void __init md_clear_select_mitigation(void)

{

	taa_select_mitigation();

	mmio_select_mitigation();

	rfds_select_mitigation();