linux-kernel - [PATCH 5.4 22/51] x86/speculation: Use cached host SPEC

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20221005113211.292737780@linuxfoundation.org>
Date:   Wed,  5 Oct 2022 13:32:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Borislav Petkov <bp@...e.de>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Subject: [PATCH 5.4 22/51] x86/speculation: Use cached host SPEC_CTRL value for guest entry/exit

From: Josh Poimboeuf <jpoimboe@...nel.org>

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: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...onical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kernel/cpu/bugs.c |   12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -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,
 		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_mit
 		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);
 	}