[ Upstream commit a7939f01672034a58ad3fdbce69bb6c665ce0024 ]
Builtin/initrd microcode will not be used the ucode loader is disabled.
But currently, save_microcode_in_initrd is always performed and it
accesses MSR_IA32_UCODE_REV even if dis_ucode_ldr is true, and in
particular even if X86_FEATURE_HYPERVISOR is set; the TDX module does not
implement the MSR and the result is a call trace at boot for TDX guests.
Mainline Linux fixed this as part of a more complex rework of microcode
caching that went into 6.7 (see in particular commits dd5e3e3ca6,
"x86/microcode/intel: Simplify early loading"; and a7939f0167203,
"x86/microcode/amd: Cache builtin/initrd microcode early"). Do the bare
minimum in stable kernels, setting initrd_gone just like mainline Linux
does in mark_initrd_gone().
Note that save_microcode_in_initrd() is not in the microcode application
path, which runs with paging disabled on 32-bit systems, so it can (and
has to) use dis_ucode_ldr instead of check_loader_disabled_ap().
Cc: stable@xxxxxxxxxxxxxxx # v6.6+
Cc: x86@xxxxxxxxxx # v6.6+
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kernel/cpu/microcode/core.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 35d39a13dc90..503b5da56685 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -214,6 +214,11 @@ static int __init save_microcode_in_initrd(void)
struct cpuinfo_x86 *c = &boot_cpu_data;
int ret = -EINVAL;
+ if (dis_ucode_ldr) {
+ ret = 0;
+ goto out;
+ }
+
switch (c->x86_vendor) {
case X86_VENDOR_INTEL:
if (c->x86 >= 6)
@@ -227,6 +230,7 @@ static int __init save_microcode_in_initrd(void)
break;
}
+out:
initrd_gone = true;
return ret;
--
2.43.0
