kernel.git/arch/x86/kernel/kvm.c, branch linux-5.18.y

x86, kvm: use correct GFP flags for preemption disabled

2022-06-06T06:48:55Z

commit baec4f5a018fe2d708fc1022330dba04b38b5fe3 upstream. Commit ddd7ed842627 ("x86/kvm: Alloc dummy async #PF token outside of raw spinlock") leads to the following Smatch static checker warning: arch/x86/kernel/kvm.c:212 kvm_async_pf_task_wake() warn: sleeping in atomic context arch/x86/kernel/kvm.c 202 raw_spin_lock(&b->lock); 203 n = _find_apf_task(b, token); 204 if (!n) { 205 /* 206 * Async #PF not yet handled, add a dummy entry for the token. 207 * Allocating the token must be down outside of the raw lock 208 * as the allocator is preemptible on PREEMPT_RT kernels. 209 */ 210 if (!dummy) { 211 raw_spin_unlock(&b->lock); --> 212 dummy = kzalloc(sizeof(*dummy), GFP_KERNEL); ^^^^^^^^^^ Smatch thinks the caller has preempt disabled. The `smdb.py preempt kvm_async_pf_task_wake` output call tree is: sysvec_kvm_asyncpf_interrupt() <- disables preempt -> __sysvec_kvm_asyncpf_interrupt() -> kvm_async_pf_task_wake() The caller is this: arch/x86/kernel/kvm.c 290 DEFINE_IDTENTRY_SYSVEC(sysvec_kvm_asyncpf_interrupt) 291 { 292 struct pt_regs *old_regs = set_irq_regs(regs); 293 u32 token; 294 295 ack_APIC_irq(); 296 297 inc_irq_stat(irq_hv_callback_count); 298 299 if (__this_cpu_read(apf_reason.enabled)) { 300 token = __this_cpu_read(apf_reason.token); 301 kvm_async_pf_task_wake(token); 302 __this_cpu_write(apf_reason.token, 0); 303 wrmsrl(MSR_KVM_ASYNC_PF_ACK, 1); 304 } 305 306 set_irq_regs(old_regs); 307 } The DEFINE_IDTENTRY_SYSVEC() is a wrapper that calls this function from the call_on_irqstack_cond(). It's inside the call_on_irqstack_cond() where preempt is disabled (unless it's already disabled). The irq_enter/exit_rcu() functions disable/enable preempt. Reported-by: Dan Carpenter Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

x86/kvm: Alloc dummy async #PF token outside of raw spinlock

2022-06-06T06:48:55Z

commit 0547758a6de3cc71a0cfdd031a3621a30db6a68b upstream. Drop the raw spinlock in kvm_async_pf_task_wake() before allocating the the dummy async #PF token, the allocator is preemptible on PREEMPT_RT kernels and must not be called from truly atomic contexts. Opportunistically document why it's ok to loop on allocation failure, i.e. why the function won't get stuck in an infinite loop. Reported-by: Yajun Deng Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

x86/kvm: Preserve BSP MSR_KVM_POLL_CONTROL across suspend/resume

2022-04-21T17:16:14Z

MSR_KVM_POLL_CONTROL is cleared on reset, thus reverting guests to host-side polling after suspend/resume. Non-bootstrap CPUs are restored correctly by the haltpoll driver because they are hot-unplugged during suspend and hot-plugged during resume; however, the BSP is not hotpluggable and remains in host-sde polling mode after the guest resume. The makes the guest pay for the cost of vmexits every time the guest enters idle. Fix it by recording BSP's haltpoll state and resuming it during guest resume. Cc: Marcelo Tosatti Signed-off-by: Wanpeng Li Message-Id: <1650267752-46796-1-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2022-04-02T19:09:02Z

Pull kvm fixes from Paolo Bonzini: - Only do MSR filtering for MSRs accessed by rdmsr/wrmsr - Documentation improvements - Prevent module exit until all VMs are freed - PMU Virtualization fixes - Fix for kvm_irq_delivery_to_apic_fast() NULL-pointer dereferences - Other miscellaneous bugfixes * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (42 commits) KVM: x86: fix sending PV IPI KVM: x86/mmu: do compare-and-exchange of gPTE via the user address KVM: x86: Remove redundant vm_entry_controls_clearbit() call KVM: x86: cleanup enter_rmode() KVM: x86: SVM: fix tsc scaling when the host doesn't support it kvm: x86: SVM: remove unused defines KVM: x86: SVM: move tsc ratio definitions to svm.h KVM: x86: SVM: fix avic spec based definitions again KVM: MIPS: remove reference to trap&emulate virtualization KVM: x86: document limitations of MSR filtering KVM: x86: Only do MSR filtering when access MSR by rdmsr/wrmsr KVM: x86/emulator: Emulate RDPID only if it is enabled in guest KVM: x86/pmu: Fix and isolate TSX-specific performance event logic KVM: x86: mmu: trace kvm_mmu_set_spte after the new SPTE was set KVM: x86/svm: Clear reserved bits written to PerfEvtSeln MSRs KVM: x86: Trace all APICv inhibit changes and capture overall status KVM: x86: Add wrappers for setting/clearing APICv inhibits KVM: x86: Make APICv inhibit reasons an enum and cleanup naming KVM: X86: Handle implicit supervisor access with SMAP KVM: X86: Rename variable smap to not_smap in permission_fault() ...

KVM: x86: fix sending PV IPI

2022-04-02T09:37:27Z

If apic_id is less than min, and (max - apic_id) is greater than KVM_IPI_CLUSTER_SIZE, then the third check condition is satisfied but the new apic_id does not fit the bitmask. In this case __send_ipi_mask should send the IPI. This is mostly theoretical, but it can happen if the apic_ids on three iterations of the loop are for example 1, KVM_IPI_CLUSTER_SIZE, 0. Fixes: aaffcfd1e82 ("KVM: X86: Implement PV IPIs in linux guest") Signed-off-by: Li RongQing Message-Id: <1646814944-51801-1-git-send-email-lirongqing@baidu.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini

x86/ibt,paravirt: Sprinkle ENDBR

2022-03-15T09:32:36Z

Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Kees Cook Acked-by: Josh Poimboeuf Link: https://lore.kernel.org/r/20220308154318.051635891@infradead.org

KVM: x86: Yield to IPI target vCPU only if it is busy

2022-02-25T15:09:35Z

When sending a call-function IPI-many to vCPUs, yield to the IPI target vCPU which is marked as preempted. but when emulating HLT, an idling vCPU will be voluntarily scheduled out and mark as preempted from the guest kernel perspective. yielding to idle vCPU is pointless and increase unnecessary vmexit, maybe miss the true preempted vCPU so yield to IPI target vCPU only if vCPU is busy and preempted Signed-off-by: Li RongQing Message-Id: <1644380201-29423-1-git-send-email-lirongqing@baidu.com> Signed-off-by: Paolo Bonzini

x86/kvm: Don't use PV TLB/yield when mwait is advertised

2022-02-25T15:09:34Z

MWAIT is advertised in host is not overcommitted scenario, however, PV TLB/sched yield should be enabled in host overcommitted scenario. Let's add the MWAIT checking when enabling PV TLB/sched yield. Signed-off-by: Wanpeng Li Message-Id: <1645777780-2581-1-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini

x86/kvm: Don't use pv tlb/ipi/sched_yield if on 1 vCPU

2022-02-18T08:36:24Z

Inspired by commit 3553ae5690a (x86/kvm: Don't use pvqspinlock code if only 1 vCPU), on a VM with only 1 vCPU, there is no need to enable pv tlb/ipi/sched_yield and we can save the memory for __pv_cpu_mask. Signed-off-by: Wanpeng Li Message-Id: <1645171838-2855-1-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini

x86/kvm: Silence per-cpu pr_info noise about KVM clocks and steal time

2022-01-07T15:44:43Z

I made the actual CPU bringup go nice and fast... and then Linux spends half a minute printing stupid nonsense about clocks and steal time for each of 256 vCPUs. Don't do that. Nobody cares. Signed-off-by: David Woodhouse Message-Id: <20211209150938.3518-12-dwmw2@infradead.org> Signed-off-by: Paolo Bonzini