diff options
Diffstat (limited to 'OvmfPkg/CpuHotplugSmm')
| -rw-r--r-- | OvmfPkg/CpuHotplugSmm/Smbase.c | 35 |
1 files changed, 29 insertions, 6 deletions
diff --git a/OvmfPkg/CpuHotplugSmm/Smbase.c b/OvmfPkg/CpuHotplugSmm/Smbase.c index 170571221d..d8f45c4313 100644 --- a/OvmfPkg/CpuHotplugSmm/Smbase.c +++ b/OvmfPkg/CpuHotplugSmm/Smbase.c @@ -220,14 +220,37 @@ SmbaseRelocate ( //
// Boot the hot-added CPU.
//
- // If the OS is benign, and so the hot-added CPU is still in RESET state,
- // then the broadcast SMI is still pending for it; it will now launch
- // directly into SMM.
+ // There are 2*2 cases to consider:
//
- // If the OS is malicious, the hot-added CPU has been booted already, and so
- // it is already spinning on the APIC ID gate. In that case, the
- // INIT-SIPI-SIPI below will be ignored.
+ // (1) The CPU was hot-added before the SMI was broadcast.
//
+ // (1.1) The OS is benign.
+ //
+ // The hot-added CPU is in RESET state, with the broadcast SMI pending
+ // for it. The directed SMI below will be ignored (it's idempotent),
+ // and the INIT-SIPI-SIPI will launch the CPU directly into SMM.
+ //
+ // (1.2) The OS is malicious.
+ //
+ // The hot-added CPU has been booted, by the OS. Thus, the hot-added
+ // CPU is spinning on the APIC ID gate. In that case, both the SMI and
+ // the INIT-SIPI-SIPI below will be ignored.
+ //
+ // (2) The CPU was hot-added after the SMI was broadcast.
+ //
+ // (2.1) The OS is benign.
+ //
+ // The hot-added CPU is in RESET state, with no SMI pending for it. The
+ // directed SMI will latch the SMI for the CPU. Then the INIT-SIPI-SIPI
+ // will launch the CPU into SMM.
+ //
+ // (2.2) The OS is malicious.
+ //
+ // The hot-added CPU is executing OS code. The directed SMI will pull
+ // the hot-added CPU into SMM, where it will start spinning on the APIC
+ // ID gate. The INIT-SIPI-SIPI will be ignored.
+ //
+ SendSmiIpi (ApicId);
SendInitSipiSipi (ApicId, PenAddress);
//
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