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Li RongQing
2ddd6bf6b6
[ Upstream commit9605505039] The commitb2798ba0b8("KVM: X86: Choose qspinlock when dedicated physical CPUs are available") states that when PV_DEDICATED=1 (vCPU has dedicated pCPU), qspinlock should be preferred regardless of PV_UNHALT. However, the current implementation doesn't reflect this: when PV_UNHALT=0, we still use virt_spin_lock() even with dedicated pCPUs. This is suboptimal because: 1. Native qspinlocks should outperform virt_spin_lock() for dedicated vCPUs irrespective of HALT exiting 2. virt_spin_lock() should only be preferred when vCPUs may be preempted (non-dedicated case) So reorder the PV spinlock checks to: 1. First handle dedicated pCPU case (disable virt_spin_lock_key) 2. Second check single CPU, and nopvspin configuration 3. Only then check PV_UNHALT support This ensures we always use native qspinlock for dedicated vCPUs, delivering pretty performance gains at high contention levels. Signed-off-by: Li RongQing <lirongqing@baidu.com> Reviewed-by: Sean Christopherson <seanjc@google.com> Tested-by: Wangyang Guo <wangyang.guo@intel.com> Link: https://lore.kernel.org/r/20250722110005.4988-1-lirongqing@baidu.com Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.