x86/bugs: Restructure RFDS mitigation

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

  [ bp: Rename the oneline helper to what it checks. ]

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/20250418161721.1855190-5-david.kaplan@amd.com

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index bc74c22e927c59315d0bbba77a7f6aaccc20b12b..2705105d9a5e3a675cc20eb78ce211ba73b17761 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -70,6 +70,9 @@ static void __init taa_apply_mitigation(void);
 static void __init mmio_select_mitigation(void);
 static void __init mmio_update_mitigation(void);
 static void __init mmio_apply_mitigation(void);
+static void __init rfds_select_mitigation(void);
+static void __init rfds_update_mitigation(void);
+static void __init rfds_apply_mitigation(void);
 static void __init srbds_select_mitigation(void);
 static void __init l1d_flush_select_mitigation(void);
 static void __init srso_select_mitigation(void);
@@ -200,6 +203,7 @@ void __init cpu_select_mitigations(void)
        mds_select_mitigation();
        taa_select_mitigation();
        mmio_select_mitigation();
+       rfds_select_mitigation();
        md_clear_select_mitigation();
        srbds_select_mitigation();
        l1d_flush_select_mitigation();
@@ -218,10 +222,12 @@ void __init cpu_select_mitigations(void)
        mds_update_mitigation();
        taa_update_mitigation();
        mmio_update_mitigation();
+       rfds_update_mitigation();
 
        mds_apply_mitigation();
        taa_apply_mitigation();
        mmio_apply_mitigation();
+       rfds_apply_mitigation();
 }
 
 /*
@@ -624,22 +630,48 @@ static const char * const rfds_strings[] = {
        [RFDS_MITIGATION_UCODE_NEEDED]          = "Vulnerable: No microcode",
 };
 
+static inline bool __init verw_clears_cpu_reg_file(void)
+{
+       return (x86_arch_cap_msr & ARCH_CAP_RFDS_CLEAR);
+}
+
 static void __init rfds_select_mitigation(void)
 {
        if (!boot_cpu_has_bug(X86_BUG_RFDS) || cpu_mitigations_off()) {
                rfds_mitigation = RFDS_MITIGATION_OFF;
                return;
        }
+
+       if (rfds_mitigation == RFDS_MITIGATION_AUTO)
+               rfds_mitigation = RFDS_MITIGATION_VERW;
+
        if (rfds_mitigation == RFDS_MITIGATION_OFF)
                return;
 
-       if (rfds_mitigation == RFDS_MITIGATION_AUTO)
+       if (verw_clears_cpu_reg_file())
+               verw_clear_cpu_buf_mitigation_selected = true;
+}
+
+static void __init rfds_update_mitigation(void)
+{
+       if (!boot_cpu_has_bug(X86_BUG_RFDS) || cpu_mitigations_off())
+               return;
+
+       if (verw_clear_cpu_buf_mitigation_selected)
                rfds_mitigation = RFDS_MITIGATION_VERW;
 
-       if (x86_arch_cap_msr & ARCH_CAP_RFDS_CLEAR)
+       if (rfds_mitigation == RFDS_MITIGATION_VERW) {
+               if (!verw_clears_cpu_reg_file())
+                       rfds_mitigation = RFDS_MITIGATION_UCODE_NEEDED;
+       }
+
+       pr_info("%s\n", rfds_strings[rfds_mitigation]);
+}
+
+static void __init rfds_apply_mitigation(void)
+{
+       if (rfds_mitigation == RFDS_MITIGATION_VERW)
                setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
-       else
-               rfds_mitigation = RFDS_MITIGATION_UCODE_NEEDED;
 }
 
 static __init int rfds_parse_cmdline(char *str)
@@ -712,7 +744,6 @@ out:
 
 static void __init md_clear_select_mitigation(void)
 {
-       rfds_select_mitigation();
 
        /*
         * As these mitigations are inter-related and rely on VERW instruction