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Commit 1ec1aced authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Greg Kroah-Hartman
Browse files

x86/speculation: Use cached host SPEC_CTRL value for guest entry/exit 



commit bbb69e8bee1bd882784947095ffb2bfe0f7c9470 upstream.

There's no need to recalculate the host value for every entry/exit.
Just use the cached value in spec_ctrl_current().

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: default avatarThadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: default avatarSuleiman Souhlal <suleiman@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8bafec7f

arch/x86/kernel/cpu/bugs.c

+1 −11
Original line number Diff line number Diff line
@@ -198,7 +198,7 @@ void __init check_bugs(void) 
void

x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest)

{

	u64 msrval, guestval, hostval = x86_spec_ctrl_base;

	u64 msrval, guestval, hostval = spec_ctrl_current();

	struct thread_info *ti = current_thread_info();



	/* Is MSR_SPEC_CTRL implemented ? */
@@ -211,15 +211,6 @@ x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest) 
		guestval = hostval & ~x86_spec_ctrl_mask;

		guestval |= guest_spec_ctrl & x86_spec_ctrl_mask;



		/* SSBD controlled in MSR_SPEC_CTRL */

		if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) ||

		    static_cpu_has(X86_FEATURE_AMD_SSBD))

			hostval |= ssbd_tif_to_spec_ctrl(ti->flags);



		/* Conditional STIBP enabled? */

		if (static_branch_unlikely(&switch_to_cond_stibp))

			hostval |= stibp_tif_to_spec_ctrl(ti->flags);



		if (hostval != guestval) {

			msrval = setguest ? guestval : hostval;

			wrmsrl(MSR_IA32_SPEC_CTRL, msrval);
@@ -1274,7 +1265,6 @@ static void __init spectre_v2_select_mitigation(void) 
		pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);



	if (spectre_v2_in_ibrs_mode(mode)) {

		/* Force it so VMEXIT will restore correctly */

		x86_spec_ctrl_base |= SPEC_CTRL_IBRS;

		write_spec_ctrl_current(x86_spec_ctrl_base, true);

	}