On Mon, Jan 15, 2024 at 11:22:02AM +0100, Paolo Bonzini wrote: > [ 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(). ... simply because save_microcode_in_initrd() is a fs_initcall and by then 32-bit has managed to enable paging. > 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; > -- Makes sense to me. Acked-by: Borislav Petkov (AMD) <bp@xxxxxxxxx> -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette