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x86/microcode: do not cache microcode if it will not be used

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No relevant upstream kernel due to refactoring in 6.7

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@vger.kernel.org # v6.6+
Cc: x86@kernel.org # v6.6+
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Paolo Bonzini 2024-01-15 11:22:02 +01:00 committed by Greg Kroah-Hartman
parent 7e881af7fb
commit d86c51e956
1 changed files with 6 additions and 0 deletions
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6
arch/x86/kernel/cpu/microcode/core.c
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@ -208,6 +208,11 @@ 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)
@ -221,6 +226,7 @@ static int __init save_microcode_in_initrd(void)
break;
}
out:
initrd_gone = true;
return ret;