Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip (53a07a14) · Commits · 戴 / test

Documentation/admin-guide/hw-vuln/mds.rst

+5 −2

Original line number	Diff line number	Diff line
		@@ -265,8 +265,11 @@ time with the option "mds=". The valid arguments for this option are:

		============ =============================================================

		Not specifying this option is equivalent to "mds=full".

		Not specifying this option is equivalent to "mds=full". For processors
		that are affected by both TAA (TSX Asynchronous Abort) and MDS,
		specifying just "mds=off" without an accompanying "tsx_async_abort=off"
		will have no effect as the same mitigation is used for both
		vulnerabilities.

		Mitigation selection guide
		--------------------------

Documentation/admin-guide/hw-vuln/tsx_async_abort.rst

+4 −1

Original line number	Diff line number	Diff line
		@@ -174,7 +174,10 @@ the option "tsx_async_abort=". The valid arguments for this option are:
		CPU is not vulnerable to cross-thread TAA attacks.
		============ =============================================================

		Not specifying this option is equivalent to "tsx_async_abort=full".
		Not specifying this option is equivalent to "tsx_async_abort=full". For
		processors that are affected by both TAA and MDS, specifying just
		"tsx_async_abort=off" without an accompanying "mds=off" will have no
		effect as the same mitigation is used for both vulnerabilities.

		The kernel command line also allows to control the TSX feature using the
		parameter "tsx=" on CPUs which support TSX control. MSR_IA32_TSX_CTRL is used

Documentation/admin-guide/kernel-parameters.txt

+11 −0

Original line number	Diff line number	Diff line
		@@ -2473,6 +2473,12 @@
		SMT on vulnerable CPUs
		off - Unconditionally disable MDS mitigation

		On TAA-affected machines, mds=off can be prevented by
		an active TAA mitigation as both vulnerabilities are
		mitigated with the same mechanism so in order to disable
		this mitigation, you need to specify tsx_async_abort=off
		too.

		Not specifying this option is equivalent to
		mds=full.

		@@ -4931,6 +4937,11 @@
		vulnerable to cross-thread TAA attacks.
		off - Unconditionally disable TAA mitigation

		On MDS-affected machines, tsx_async_abort=off can be
		prevented by an active MDS mitigation as both vulnerabilities
		are mitigated with the same mechanism so in order to disable
		this mitigation, you need to specify mds=off too.

		Not specifying this option is equivalent to
		tsx_async_abort=full. On CPUs which are MDS affected
		and deploy MDS mitigation, TAA mitigation is not

arch/x86/kernel/cpu/bugs.c

+28 −2

Original line number	Diff line number	Diff line
		@@ -39,6 +39,7 @@ static void __init spectre_v2_select_mitigation(void);
		static void __init ssb_select_mitigation(void);
		static void __init l1tf_select_mitigation(void);
		static void __init mds_select_mitigation(void);
		static void __init mds_print_mitigation(void);
		static void __init taa_select_mitigation(void);

		/* The base value of the SPEC_CTRL MSR that always has to be preserved. */
		@@ -108,6 +109,12 @@ void __init check_bugs(void)
		mds_select_mitigation();
		taa_select_mitigation();

		/*
		* As MDS and TAA mitigations are inter-related, print MDS
		* mitigation until after TAA mitigation selection is done.
		*/
		mds_print_mitigation();

		arch_smt_update();

		#ifdef CONFIG_X86_32
		@@ -245,6 +252,12 @@ static void __init mds_select_mitigation(void)
		(mds_nosmt \|\| cpu_mitigations_auto_nosmt()))
		cpu_smt_disable(false);
		}
		}

		static void __init mds_print_mitigation(void)
		{
		if (!boot_cpu_has_bug(X86_BUG_MDS) \|\| cpu_mitigations_off())
		return;

		pr_info("%s\n", mds_strings[mds_mitigation]);
		}
		@@ -304,8 +317,12 @@ static void __init taa_select_mitigation(void)
		return;
		}

		/* TAA mitigation is turned off on the cmdline (tsx_async_abort=off) */
		if (taa_mitigation == TAA_MITIGATION_OFF)
		/*
		* 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)
		goto out;

		if (boot_cpu_has(X86_FEATURE_MD_CLEAR))
		@@ -339,6 +356,15 @@ static void __init taa_select_mitigation(void)
		if (taa_nosmt \|\| cpu_mitigations_auto_nosmt())
		cpu_smt_disable(false);

		/*
		* Update MDS mitigation, if necessary, as the mds_user_clear is
		* now enabled for TAA mitigation.
		*/
		if (mds_mitigation == MDS_MITIGATION_OFF &&
		boot_cpu_has_bug(X86_BUG_MDS)) {
		mds_mitigation = MDS_MITIGATION_FULL;
		mds_select_mitigation();
		}
		out:
		pr_info("%s\n", taa_strings[taa_mitigation]);
		}

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