Sean Christopherson b4886fab6f KVM: Add a module param to allow enabling virtualization when KVM is loaded ... Add an on-by-default module param, enable_virt_at_load, to let userspace force virtualization to be enabled in hardware when KVM is initialized, i.e. just before /dev/kvm is exposed to userspace. Enabling virtualization during KVM initialization allows userspace to avoid the additional latency when creating/destroying the first/last VM (or more specifically, on the 0=>1 and 1=>0 edges of creation/destruction). Now that KVM uses the cpuhp framework to do per-CPU enabling, the latency could be non-trivial as the cpuhup bringup/teardown is serialized across CPUs, e.g. the latency could be problematic for use case that need to spin up VMs quickly. Prior to commit 10474ae894 ("KVM: Activate Virtualization On Demand"), KVM _unconditionally_ enabled virtualization during load, i.e. there's no fundamental reason KVM needs to dynamically toggle virtualization. These days, the only known argument for not enabling virtualization is to allow KVM to be autoloaded without blocking other out-of-tree hypervisors, and such use cases can simply change the module param, e.g. via command line. Note, the aforementioned commit also mentioned that enabling SVM (AMD's virtualization extensions) can result in "using invalid TLB entries". It's not clear whether the changelog was referring to a KVM bug, a CPU bug, or something else entirely. Regardless, leaving virtualization off by default is not a robust "fix", as any protection provided is lost the instant userspace creates the first VM. Reviewed-by: Chao Gao <chao.gao@intel.com> Acked-by: Kai Huang <kai.huang@intel.com> Reviewed-by: Kai Huang <kai.huang@intel.com> Tested-by: Farrah Chen <farrah.chen@intel.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-ID: <20240830043600.127750-8-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>		2024-09-04 11:02:33 -04:00
..
async_pf.c	Revert "KVM: async_pf: avoid recursive flushing of work items"	2024-06-03 08:55:55 -07:00
async_pf.h	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 504	2019-06-19 17:09:56 +02:00
binary_stats.c	KVM: stats: remove dead stores	2021-08-13 03:35:15 -04:00
coalesced_mmio.c	KVM: destruct kvm_io_device while unregistering it from kvm_io_bus	2023-06-13 14:18:09 -07:00
coalesced_mmio.h	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
dirty_ring.c	KVM: Discard zero mask with function kvm_dirty_ring_reset	2024-06-20 17:20:11 -04:00
eventfd.c	KVM: eventfd: Use synchronize_srcu_expedited() on shutdown	2024-08-13 12:09:35 -04:00
guest_memfd.c	KVM: guest_memfd: abstract how prepared folios are recorded	2024-07-26 14:46:15 -04:00
irqchip.c	KVM: Setup empty IRQ routing when creating a VM	2024-06-11 14:18:34 -07:00
Kconfig	KVM: rename CONFIG_HAVE_KVM_GMEM_* to CONFIG_HAVE_KVM_ARCH_GMEM_*	2024-07-26 14:46:14 -04:00
kvm_main.c	KVM: Add a module param to allow enabling virtualization when KVM is loaded	2024-09-04 11:02:33 -04:00
kvm_mm.h	KVM: Drop unused @may_block param from gfn_to_pfn_cache_invalidate_start()	2024-04-11 12:58:53 -07:00
Makefile.kvm	KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory	2023-11-14 08:01:03 -05:00
pfncache.c	KVM: Validate hva in kvm_gpc_activate_hva() to fix __kvm_gpc_refresh() WARN	2024-06-28 08:31:46 -07:00
vfio.c	KVM: Treat the device list as an rculist	2024-04-25 13:19:55 +01:00
vfio.h	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00