Commit 0fa4a313 authored by Marc Zyngier's avatar Marc Zyngier
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KVM: arm64: Document why pause cannot be turned into a flag 



It would be tempting to turn the 'pause' state into a flag.

However, this cannot easily be done as it is updated out of context,
while all the flags expect to only be updated from the vcpu thread.
Turning it into a flag would require to make all flag updates
atomic, which isn't necessary desireable.

Document this, and take this opportunity to move the field next
to the flag sets, filling a hole in the vcpu structure.

Reviewed-by: default avatarFuad Tabba <tabba@google.com>
Reviewed-by: default avatarReiji Watanabe <reijiw@google.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 54ddda91

arch/arm64/include/asm/kvm_host.h

+9 −3
Original line number Diff line number Diff line
@@ -341,6 +341,15 @@ struct kvm_vcpu_arch { 
	/* State flags for kernel bookkeeping, unused by the hypervisor code */

	u8 sflags;



	/*

	 * Don't run the guest (internal implementation need).

	 *

	 * Contrary to the flags above, this is set/cleared outside of

	 * a vcpu context, and thus cannot be mixed with the flags

	 * themselves (or the flag accesses need to be made atomic).

	 */

	bool pause;



	/*

	 * We maintain more than a single set of debug registers to support

	 * debugging the guest from the host and to maintain separate host and
@@ -394,9 +403,6 @@ struct kvm_vcpu_arch { 
	/* vcpu power state */

	struct kvm_mp_state mp_state;



	/* Don't run the guest (internal implementation need) */

	bool pause;



	/* Cache some mmu pages needed inside spinlock regions */

	struct kvm_mmu_memory_cache mmu_page_cache;