[Xen-devel] [PATCH v2 09/17] x86/bugs: add lfence mitigation to spectre v2 and no meltdown for Hygon

[Pu Wen <puwen@xxxxxxxx>]

To share codes between AMD and Hygon to mitigate Spectre V2 Retpoline
vulnerability, rename macros SPECTRE_V2_RETPOLINE_MINIMAL_AMD to
SPECTRE_V2_RETPOLINE_MINIMAL_LFENCE, and SPECTRE_V2_CMD_RETPOLINE_AMD
to SPECTRE_V2_CMD_RETPOLINE_LFENCE.

As Hygon processors is not affected by meltdown vulnerability as AMD's,
so add exception in array cpu_no_meltdown[] for it.

Signed-off-by: Pu Wen <puwen@xxxxxxxx>
---
 arch/x86/include/asm/nospec-branch.h |  4 ++--
 arch/x86/kernel/cpu/bugs.c           | 28 +++++++++++++++-------------
 arch/x86/kernel/cpu/common.c         |  1 +
 3 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h 
b/arch/x86/include/asm/nospec-branch.h
index f6f6c63..aad6b9c 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -211,9 +211,9 @@
 enum spectre_v2_mitigation {
        SPECTRE_V2_NONE,
        SPECTRE_V2_RETPOLINE_MINIMAL,
-       SPECTRE_V2_RETPOLINE_MINIMAL_AMD,
+       SPECTRE_V2_RETPOLINE_MINIMAL_LFENCE,
        SPECTRE_V2_RETPOLINE_GENERIC,
-       SPECTRE_V2_RETPOLINE_AMD,
+       SPECTRE_V2_RETPOLINE_LFENCE,
        SPECTRE_V2_IBRS,
 };
 
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 5c0ea39..5d0ba61 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -121,15 +121,15 @@ enum spectre_v2_mitigation_cmd {
        SPECTRE_V2_CMD_FORCE,
        SPECTRE_V2_CMD_RETPOLINE,
        SPECTRE_V2_CMD_RETPOLINE_GENERIC,
-       SPECTRE_V2_CMD_RETPOLINE_AMD,
+       SPECTRE_V2_CMD_RETPOLINE_LFENCE,
 };
 
 static const char *spectre_v2_strings[] = {
        [SPECTRE_V2_NONE]                       = "Vulnerable",
        [SPECTRE_V2_RETPOLINE_MINIMAL]          = "Vulnerable: Minimal generic 
ASM retpoline",
-       [SPECTRE_V2_RETPOLINE_MINIMAL_AMD]      = "Vulnerable: Minimal AMD ASM 
retpoline",
+       [SPECTRE_V2_RETPOLINE_MINIMAL_LFENCE]   = "Vulnerable: Minimal LFENCE 
ASM retpoline",
        [SPECTRE_V2_RETPOLINE_GENERIC]          = "Mitigation: Full generic 
retpoline",
-       [SPECTRE_V2_RETPOLINE_AMD]              = "Mitigation: Full AMD 
retpoline",
+       [SPECTRE_V2_RETPOLINE_LFENCE]           = "Mitigation: Full LFENCE 
retpoline",
 };
 
 #undef pr_fmt
@@ -260,7 +260,7 @@ static const struct {
        { "off",               SPECTRE_V2_CMD_NONE,              false },
        { "on",                SPECTRE_V2_CMD_FORCE,             true },
        { "retpoline",         SPECTRE_V2_CMD_RETPOLINE,         false },
-       { "retpoline,amd",     SPECTRE_V2_CMD_RETPOLINE_AMD,     false },
+       { "retpoline,lfence",     SPECTRE_V2_CMD_RETPOLINE_LFENCE,     false },
        { "retpoline,generic", SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
        { "auto",              SPECTRE_V2_CMD_AUTO,              false },
 };
@@ -292,16 +292,17 @@ static enum spectre_v2_mitigation_cmd __init 
spectre_v2_parse_cmdline(void)
        }
 
        if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
-            cmd == SPECTRE_V2_CMD_RETPOLINE_AMD ||
+            cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE ||
             cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC) &&
            !IS_ENABLED(CONFIG_RETPOLINE)) {
                pr_err("%s selected but not compiled in. Switching to AUTO 
select\n", mitigation_options[i].option);
                return SPECTRE_V2_CMD_AUTO;
        }
 
-       if (cmd == SPECTRE_V2_CMD_RETPOLINE_AMD &&
+       if (cmd == SPECTRE_V2_CMD_RETPOLINE_LFENCE &&
+           boot_cpu_data.x86_vendor != X86_VENDOR_HYGON &&
            boot_cpu_data.x86_vendor != X86_VENDOR_AMD) {
-               pr_err("retpoline,amd selected but CPU is not AMD. Switching to 
AUTO select\n");
+               pr_err("retpoline,amd selected but CPU is not AMD or Hygon. 
Switching to AUTO select\n");
                return SPECTRE_V2_CMD_AUTO;
        }
 
@@ -352,9 +353,9 @@ static void __init spectre_v2_select_mitigation(void)
                if (IS_ENABLED(CONFIG_RETPOLINE))
                        goto retpoline_auto;
                break;
-       case SPECTRE_V2_CMD_RETPOLINE_AMD:
+       case SPECTRE_V2_CMD_RETPOLINE_LFENCE:
                if (IS_ENABLED(CONFIG_RETPOLINE))
-                       goto retpoline_amd;
+                       goto retpoline_lfence;
                break;
        case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
                if (IS_ENABLED(CONFIG_RETPOLINE))
@@ -369,14 +370,15 @@ static void __init spectre_v2_select_mitigation(void)
        return;
 
 retpoline_auto:
-       if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
-       retpoline_amd:
+       if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
+           boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
+       retpoline_lfence:
                if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
                        pr_err("Spectre mitigation: LFENCE not serializing, 
switching to generic retpoline\n");
                        goto retpoline_generic;
                }
-               mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_AMD :
-                                        SPECTRE_V2_RETPOLINE_MINIMAL_AMD;
+               mode = retp_compiler() ? SPECTRE_V2_RETPOLINE_LFENCE :
+                                        SPECTRE_V2_RETPOLINE_MINIMAL_LFENCE;
                setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
                setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
        } else {
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index eb4cb3e..06b3168 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -968,6 +968,7 @@ static const __initconst struct x86_cpu_id 
cpu_no_speculation[] = {
 
 static const __initconst struct x86_cpu_id cpu_no_meltdown[] = {
        { X86_VENDOR_AMD },
+       { X86_VENDOR_HYGON },
        {}
 };
 
-- 
2.7.4


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