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Message-ID: <20240830043600.127750-1-seanjc@google.com>
Date: Thu, 29 Aug 2024 21:35:50 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
Oliver Upton <oliver.upton@...ux.dev>, Tianrui Zhao <zhaotianrui@...ngson.cn>,
Bibo Mao <maobibo@...ngson.cn>, Huacai Chen <chenhuacai@...nel.org>,
Anup Patel <anup@...infault.org>, Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
kvmarm@...ts.linux.dev, loongarch@...ts.linux.dev, linux-mips@...r.kernel.org,
kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org, Chao Gao <chao.gao@...el.com>,
Kai Huang <kai.huang@...el.com>, Farrah Chen <farrah.chen@...el.com>
Subject: [PATCH v4 00/10] KVM: Register cpuhp/syscore callbacks when enabling virt
Register KVM's cpuhp and syscore callbacks when enabling virtualization in
hardware, as the sole purpose of said callbacks is to disable and re-enable
virtualization as needed.
The primary motivation for this series is to simplify dealing with enabling
virtualization for Intel's TDX, which needs to enable virtualization
when kvm-intel.ko is loaded, i.e. long before the first VM is created.
That said, this is a nice cleanup on its own. By registering the callbacks
on-demand, the callbacks themselves don't need to check kvm_usage_count,
because their very existence implies a non-zero count.
Patch 1 (re)adds a dedicated lock for kvm_usage_count. Hopefully it's a
temporary lock, as we can likely fix the cpus_read_lock() vs. kvm_lock mess
for good by switching vm_list to an (S)RCU-protected list.
v4:
- Collect more reviews.
- Fix documentation for kvm_usage_lock. [Kai]
- Add a blurb in locking.rst to call out that cpus_read_lock() vs kvm_lock is
a general problem.
- Add a paragraph in the locking patch to suggest switching vm_list to an
(S)RCU-protected list, so that walkers don't need to take kvm_lock.
- Add an example call chain for the other cpus_read_lock() vs kvm_lock issues
that are lurking.
- Enable the module param by default from the get-go. [Paolo]
- Rename even more APIs/symbols (all of 'em I could find). [Paolo]
- Clarify that it's the 0=>1 VM creation that's problematic, not simply the
creation of the very first VM. [Paolo]
- Document enable_virt_at_load, and call out the (dis)advantages of enabling
virtualization when KVM is loaded.
- Drop the WARN on kvm_usage_count being elevated at the end of
kvm_uninit_virtualization(), as it's annoyingly difficult to keep the WARN
and still allow arch code (i.e. TDX) to enable virtualization during setup.
v3:
- https://lore.kernel.org/all/20240608000639.3295768-1-seanjc@google.com
- Collect reviews/acks.
- Switch to kvm_usage_lock in a dedicated patch, Cc'd for stable@. [Chao]
- Enable virt at load by default. [Chao]
- Add comments to document how kvm_arch_{en,dis}able_virtualization() fit
into the overall flow. [Kai]
v2:
- https://lore.kernel.org/all/20240522022827.1690416-1-seanjc@google.com
- Use a dedicated mutex to avoid lock inversion issues between kvm_lock and
the cpuhp lock.
- Register emergency disable callbacks on-demand. [Kai]
- Drop an unintended s/junk/ign rename. [Kai]
- Decrement kvm_usage_count on failure. [Chao]
v1: https://lore.kernel.org/all/20240425233951.3344485-1-seanjc@google.com
Sean Christopherson (10):
KVM: Use dedicated mutex to protect kvm_usage_count to avoid deadlock
KVM: Register cpuhp and syscore callbacks when enabling hardware
KVM: Rename symbols related to enabling virtualization hardware
KVM: Rename arch hooks related to per-CPU virtualization enabling
KVM: MIPS: Rename virtualization {en,dis}abling APIs to match common
KVM
KVM: x86: Rename virtualization {en,dis}abling APIs to match common
KVM
KVM: Add a module param to allow enabling virtualization when KVM is
loaded
KVM: Add arch hooks for enabling/disabling virtualization
x86/reboot: Unconditionally define cpu_emergency_virt_cb typedef
KVM: x86: Register "emergency disable" callbacks when virt is enabled
.../admin-guide/kernel-parameters.txt | 17 ++
Documentation/virt/kvm/locking.rst | 31 +-
arch/arm64/kvm/arm.c | 6 +-
arch/loongarch/kvm/main.c | 4 +-
arch/mips/include/asm/kvm_host.h | 4 +-
arch/mips/kvm/mips.c | 8 +-
arch/mips/kvm/vz.c | 8 +-
arch/riscv/kvm/main.c | 4 +-
arch/x86/include/asm/kvm-x86-ops.h | 4 +-
arch/x86/include/asm/kvm_host.h | 7 +-
arch/x86/include/asm/reboot.h | 2 +-
arch/x86/kvm/svm/svm.c | 19 +-
arch/x86/kvm/vmx/main.c | 6 +-
arch/x86/kvm/vmx/vmx.c | 10 +-
arch/x86/kvm/vmx/x86_ops.h | 5 +-
arch/x86/kvm/x86.c | 26 +-
include/linux/kvm_host.h | 18 +-
virt/kvm/kvm_main.c | 270 +++++++++---------
18 files changed, 251 insertions(+), 198 deletions(-)
base-commit: 15e1c3d65975524c5c792fcd59f7d89f00402261
--
2.46.0.469.g59c65b2a67-goog
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