KVM: x86/pmu: Defer counter emulated overflow via pmc->prev_counter

KVM: x86/pmu: Defer counter emulated overflow via pmc->prev_counter

Defer reprogramming counters and handling overflow via KVM_REQ_PMU
when incrementing counters.  KVM skips emulated WRMSR in the VM-Exit
fastpath, the fastpath runs with IRQs disabled, skipping instructions
can increment and reprogram counters, reprogramming counters can
sleep, and sleeping is disallowed while IRQs are disabled.

 [*] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:580
 [*] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 2981888, name: CPU 15/KVM
 [*] preempt_count: 1, expected: 0
 [*] RCU nest depth: 0, expected: 0
 [*] INFO: lockdep is turned off.
 [*] irq event stamp: 0
 [*] hardirqs last  enabled at (0): [<0000000000000000>] 0x0
 [*] hardirqs last disabled at (0): [<ffffffff8121222a>] copy_process+0x146a/0x62d0
 [*] softirqs last  enabled at (0): [<ffffffff81212269>] copy_process+0x14a9/0x62d0
 [*] softirqs last disabled at (0): [<0000000000000000>] 0x0
 [*] Preemption disabled at:
 [*] [<ffffffffc2063fc1>] vcpu_enter_guest+0x1001/0x3dc0 [kvm]
 [*] CPU: 17 PID: 2981888 Comm: CPU 15/KVM Kdump: 5.19.0-rc1-g239111db364c-dirty #2
 [*] Call Trace:
 [*]  <TASK>
 [*]  dump_stack_lvl+0x6c/0x9b
 [*]  __might_resched.cold+0x22e/0x297
 [*]  __mutex_lock+0xc0/0x23b0
 [*]  perf_event_ctx_lock_nested+0x18f/0x340
 [*]  perf_event_pause+0x1a/0x110
 [*]  reprogram_counter+0x2af/0x1490 [kvm]
 [*]  kvm_pmu_trigger_event+0x429/0x950 [kvm]
 [*]  kvm_skip_emulated_instruction+0x48/0x90 [kvm]
 [*]  handle_fastpath_set_msr_irqoff+0x349/0x3b0 [kvm]
 [*]  vmx_vcpu_run+0x268e/0x3b80 [kvm_intel]
 [*]  vcpu_enter_guest+0x1d22/0x3dc0 [kvm]

Add a field to kvm_pmc to track the previous counter value in order
to defer overflow detection to kvm_pmu_handle_event() (the counter must
be paused before handling overflow, and that may increment the counter).

Opportunistically shrink sizeof(struct kvm_pmc) a bit.

Suggested-by: Wanpeng Li <wanpengli@tencent.com>
Fixes: 9cd803d496e7 ("KVM: x86: Update vPMCs when retiring instructions")
Signed-off-by: Like Xu <likexu@tencent.com>
Link: https://lore.kernel.org/r/20220831085328.45489-6-likexu@tencent.com
[sean: avoid re-triggering KVM_REQ_PMU on overflow, tweak changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220923001355.3741194-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>