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struct sgx_encl should be protected with the mutex sgx_encl->lock. One exception is sgx_encl->page_cnt that is incremented (in sgx_encl_grow()) when an enclave page is added to the enclave. The reason the mutex is not held is to allow the reclaimer to be called directly if there are no EPC pages (in support of a new VA page) available at the time. Incrementing sgx_encl->page_cnt without sgc_encl->lock held is currently (before SGX2) safe from concurrent updates because all paths in which sgx_encl_grow() is called occur before enclave initialization and are protected with an atomic operation on SGX_ENCL_IOCTL. SGX2 includes support for dynamically adding pages after enclave initialization where the protection of SGX_ENCL_IOCTL is not available. Make direct reclaim of EPC pages optional when new VA pages are added to the enclave. Essentially the existing "reclaim" flag used when regular EPC pages are added to an enclave becomes available to the caller when used to allocate VA pages instead of always being "true". When adding pages without invoking the reclaimer it is possible to do so with sgx_encl->lock held, gaining its protection against concurrent updates to sgx_encl->page_cnt after enclave initialization. No functional change. Reported-by: Haitao Huang <haitao.huang@intel.com> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Link: https://lkml.kernel.org/r/42c5934c229982ee67982bb97c6ab34bde758620.1652137848.git.reinette.chatre@intel.com
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.