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: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index e4d6159..89d6b5e 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -208,7 +208,7 @@ 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 ? */
@@ -221,15 +221,6 @@ 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);
@@ -1390,7 +1381,6 @@ 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);
        }