x86/sgx: Remove unnecessary kmap() from sgx_ioc_enclave_init()

mainline inclusion
from mainline-v5.13-rc1
commit 633b0616
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4SIGI


CVE: NA

--------------------------------

kmap() is inefficient and is being replaced by kmap_local_page(), if
possible. There is no readily apparent reason why initp_page needs to be
allocated and kmap'ed() except that 'sigstruct' needs to be page-aligned
and 'token' 512 byte-aligned.

Rather than change it to kmap_local_page(), use kmalloc() instead
because kmalloc() can give this alignment when allocating PAGE_SIZE
bytes.

Remove the alloc_page()/kmap() and replace with kmalloc(PAGE_SIZE, ...)
to get a page aligned kernel address.

In addition, add a comment to document the alignment requirements so that
others don't attempt to 'fix' this again.

 [ bp: Massage commit message. ]

Intel-SIG: commit 633b0616 x86/sgx: Remove unnecessary kmap() from sgx_ioc_enclave_init()
Backport for SGX Foundations support

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210324182246.2484875-1-ira.weiny@intel.com


Signed-off-by: Fan Du <fan.du@intel.com> #openEuler_contributor
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
Reviewed-by: Bamvor Zhang <bamvor.zhang@suse.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>