[Xen-devel] [PATCH 2/4] x86/ucode: Fix error paths in apply_microcode()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

In the unlikley case that patch application completes, but the resutling
revision isn't expected, sig->rev doesn't get updated to match reality.

It will get adjusted the next time collect_cpu_info() gets called, but in the
meantime Xen might operate on a state value.  Nothing good will come of this.

Rewrite the logic to always update the stashed revision, before worring about
whether the attempt was a success or failure.

Take the opportunity to make the printk() messages as consistent as possible.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
-CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/cpu/microcode/amd.c   | 14 +++++++-------
 xen/arch/x86/cpu/microcode/intel.c | 22 +++++++++++-----------
 2 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/xen/arch/x86/cpu/microcode/amd.c b/xen/arch/x86/cpu/microcode/amd.c
index d4b2874de6..a053e43923 100644
--- a/xen/arch/x86/cpu/microcode/amd.c
+++ b/xen/arch/x86/cpu/microcode/amd.c
@@ -229,11 +229,11 @@ static enum microcode_match_result compare_patch(
 
 static int apply_microcode(const struct microcode_patch *patch)
 {
-    uint32_t rev;
     int hw_err;
     unsigned int cpu = smp_processor_id();
     struct cpu_signature *sig = &per_cpu(cpu_sig, cpu);
     const struct microcode_header_amd *hdr;
+    uint32_t rev, old_rev = sig->rev;
 
     if ( !patch )
         return -ENOENT;
@@ -249,6 +249,7 @@ static int apply_microcode(const struct microcode_patch 
*patch)
 
     /* get patch id after patching */
     rdmsrl(MSR_AMD_PATCHLEVEL, rev);
+    sig->rev = rev;
 
     /*
      * Some processors leave the ucode blob mapping as UC after the update.
@@ -259,15 +260,14 @@ static int apply_microcode(const struct microcode_patch 
*patch)
     /* check current patch id and patch's id for match */
     if ( hw_err || (rev != hdr->patch_id) )
     {
-        printk(KERN_ERR "microcode: CPU%d update from revision "
-               "%#x to %#x failed\n", cpu, rev, hdr->patch_id);
+        printk(XENLOG_ERR
+               "microcode: CPU%u update rev %#x to %#x failed, result %#x\n",
+               cpu, old_rev, hdr->patch_id, rev);
         return -EIO;
     }
 
-    printk(KERN_WARNING "microcode: CPU%d updated from revision %#x to %#x\n",
-           cpu, sig->rev, hdr->patch_id);
-
-    sig->rev = rev;
+    printk(XENLOG_WARNING "microcode: CPU%u updated from revision %#x to 
%#x\n",
+           cpu, old_rev, hdr->patch_id);
 
     return 0;
 }
diff --git a/xen/arch/x86/cpu/microcode/intel.c 
b/xen/arch/x86/cpu/microcode/intel.c
index 5e9c2a9c7f..6ac5f98694 100644
--- a/xen/arch/x86/cpu/microcode/intel.c
+++ b/xen/arch/x86/cpu/microcode/intel.c
@@ -278,10 +278,10 @@ static enum microcode_match_result compare_patch(
 static int apply_microcode(const struct microcode_patch *patch)
 {
     uint64_t msr_content;
-    unsigned int val[2];
-    unsigned int cpu_num = raw_smp_processor_id();
+    unsigned int cpu = smp_processor_id();
     struct cpu_signature *sig = &this_cpu(cpu_sig);
     const struct microcode_intel *mc_intel;
+    uint32_t rev, old_rev = sig->rev;
 
     if ( !patch )
         return -ENOENT;
@@ -302,20 +302,20 @@ static int apply_microcode(const struct microcode_patch 
*patch)
 
     /* get the current revision from MSR 0x8B */
     rdmsrl(MSR_IA32_UCODE_REV, msr_content);
-    val[1] = (uint32_t)(msr_content >> 32);
+    sig->rev = rev = msr_content >> 32;
 
-    if ( val[1] != mc_intel->hdr.rev )
+    if ( rev != mc_intel->hdr.rev )
     {
-        printk(KERN_ERR "microcode: CPU%d update from revision "
-               "%#x to %#x failed. Resulting revision is %#x.\n", cpu_num,
-               sig->rev, mc_intel->hdr.rev, val[1]);
+        printk(XENLOG_ERR
+               "microcode: CPU%u update rev %#x to %#x failed, result %#x\n",
+               cpu, old_rev, mc_intel->hdr.rev, rev);
         return -EIO;
     }
-    printk(KERN_INFO "microcode: CPU%d updated from revision "
-           "%#x to %#x, date = %04x-%02x-%02x\n",
-           cpu_num, sig->rev, val[1], mc_intel->hdr.year,
+
+    printk(XENLOG_WARNING
+           "microcode: CPU%u updated from revision %#x to %#x, date = 
%04x-%02x-%02x\n",
+           cpu, old_rev, rev, mc_intel->hdr.year,
            mc_intel->hdr.month, mc_intel->hdr.day);
-    sig->rev = val[1];
 
     return 0;
 }
-- 
2.11.0


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