Re: [Xen-devel] [PATCH for-4.12] x86: Improve the efficiency of domain_relinquish_resources()

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Feb 21, 2019 at 12:22:13PM +0000, Andrew Cooper wrote:
> pci_release_devices() takes the global PCI lock.  Once pci_release_devices()
> has completed, it will be called redundantly each time paging_teardown() and
> vcpu_destroy_pagetables() continue.
> 
> This is liable to be millions of times for a reasonably sized guest, and is a
> serialising bottleneck now that domain_kill() can be run concurrently on
> different domains.
> 
> Instead of propagating the opencoding of the relinquish state machine, take
> the opportunity to clean it up.
> 
> Leave a proper set of comments explaining that domain_relinquish_resources()
> implements a co-routine.  Introduce a documented PROGRESS() macro to avoid
> latent bugs such as the RELMEM_xen case, and make the new PROG_* states
> private to domain_relinquish_resources().
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>

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