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hyperv: Fix CPU hotadd

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The following is from the Hyper-V specification v6.0b.

Cpuid leaf 0x40000003 EDX:

Bit 3: Support for physical CPU dynamic partitioning events is
available.

When Windows determines to be running under a hypervisor, it will
require this cpuid bit to be set to support dynamic CPU operations.

Cpuid leaf 0x40000004 EAX:

Bit 5: Recommend using relaxed timing for this partition. If
used, the VM should disable any watchdog timeouts that
rely on the timely delivery of external interrupts.

This bit has been figured out as required after seeing guest BSOD
when CPU hotplug bit is enabled. Race conditions seem to arise after a
hotplug operation, when a system watchdog has expired.

Closes #1799.

Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>
(cherry picked from commit 5b168f54a6)
Signed-off-by: Rob Bradford <robert.bradford@intel.com>
This commit is contained in:
Anatol Belski 2021-03-25 17:40:04 +01:00 committed by Rob Bradford
parent 84b3992146
commit 498939c297
1 changed files with 9 additions and 1 deletions
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10
vmm/src/cpu.rs
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@ -742,10 +742,18 @@ impl CpuManager {
| 1 << 2 // AccessSynicRegs
| 1 << 3 // AccessSyntheticTimerRegs
| 1 << 9, // AccessPartitionReferenceTsc
edx: 1 << 3, // CPU dynamic partitioning
..Default::default()
})
.map_err(Error::CpuidKvmHyperV)?;
for i in 0x4000_0004..=0x4000_000a {
cpuid
.push(CpuIdEntry {
function: 0x4000_0004,
eax: 1 << 5, // Recommend relaxed timing
..Default::default()
})
.map_err(Error::CpuidKvmHyperV)?;
for i in 0x4000_0005..=0x4000_000a {
cpuid
.push(CpuIdEntry {
function: i,