On Mon, 4 Dec 2017 21:35:23 +0100
Christoffer Dall <cdall@kernel.org> wrote:
> From: Christoffer Dall <christoffer.dall@linaro.org>
>
> As we're about to call vcpu_load() from architecture-specific
> implementations of the KVM vcpu ioctls, but yet we access data
> structures protected by the vcpu->mutex in the generic code, factor
> this logic out from vcpu_load().
>
> x86 is the only architecture which calls vcpu_load() outside of the main
> vcpu ioctl function, and these calls will no longer take the vcpu mutex
> following this patch. However, with the exception of
> kvm_arch_vcpu_postcreate (see below), the callers are either in the
> creation or destruction path of the VCPU, which means there cannot be
> any concurrent access to the data structure, because the file descriptor
> is not yet accessible, or is already gone.
>
> kvm_arch_vcpu_postcreate makes the newly created vcpu potentially
> accessible by other in-kernel threads through the kvm->vcpus array, and
> we therefore take the vcpu mutex in this case directly.
>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> ---
> arch/x86/kvm/vmx.c | 4 +---
> arch/x86/kvm/x86.c | 20 +++++++-------------
> include/linux/kvm_host.h | 2 +-
> virt/kvm/kvm_main.c | 17 ++++++-----------
> 4 files changed, 15 insertions(+), 28 deletions(-)
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
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