Messages in this thread Patch in this message | | | From | Ashok Raj <> | Subject | [PATCH v3 1/5] x86/microcode/intel: Check against CPU signature before saving microcode | Date | Wed, 17 Aug 2022 05:11:23 +0000 |
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When save_microcode_patch() is looking to replace an existing microcode in the cache, current code is *only* checks the CPU sig/pf in the main header. Microcode can carry additional sig/pf combinations in the extended signature table, which is completely missed today.
For e.g. Current patch is a multi-stepping patch and new incoming patch is a specific patch just for this CPUs stepping.
patch1: fms3 <--- header FMS ... ext_sig: fms1 fms2
patch2: new fms2 <--- header FMS
Current code takes only fms3 and checks with patch2 fms2.
saved_patch.header.fms3 != new_patch.header.fms2, so save_microcode_patch saves it to the end of list instead of replacing patch1 with patch2.
There is no functional user observable issue since find_patch() skips patch versions that are <= current_patch and will land on patch2 properly.
Nevertheless this will just end up storing every patch that isn't required. Kernel just needs to store the latest patch. Otherwise its a memory leak that sits in kernel and never used.
Cc: stable@vger.kernel.org Fixes: fe055896c040 ("x86/microcode: Merge the early microcode loader") Tested-by: William Xie <william.xie@intel.com> Reported-by: William Xie <william.xie@intel.com> Signed-off-by: Ashok Raj <ashok.raj@intel.com> --- arch/x86/kernel/cpu/microcode/intel.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c index 025c8f0cd948..c4b11e2fbe33 100644 --- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -114,10 +114,18 @@ static void save_microcode_patch(struct ucode_cpu_info *uci, void *data, unsigne list_for_each_entry_safe(iter, tmp, µcode_cache, plist) { mc_saved_hdr = (struct microcode_header_intel *)iter->data; - sig = mc_saved_hdr->sig; - pf = mc_saved_hdr->pf; - if (find_matching_signature(data, sig, pf)) { + sig = uci->cpu_sig.sig; + pf = uci->cpu_sig.pf; + + /* + * Compare the current CPUs signature with the ones in the + * cache to identify the right candidate to replace. At any + * given time, we should have no more than one valid patch + * file for a given CPU fms+pf in the cache list. + */ + + if (find_matching_signature(iter->data, sig, pf)) { prev_found = true; if (mc_hdr->rev <= mc_saved_hdr->rev) -- 2.32.0
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