linux/Documentation/x86
Kai Huang b0c7459be0 x86/sgx: Wipe out EREMOVE from sgx_free_epc_page()
EREMOVE takes a page and removes any association between that page and
an enclave. It must be run on a page before it can be added into another
enclave. Currently, EREMOVE is run as part of pages being freed into the
SGX page allocator. It is not expected to fail, as it would indicate a
use-after-free of EPC pages. Rather than add the page back to the pool
of available EPC pages, the kernel intentionally leaks the page to avoid
additional errors in the future.

However, KVM does not track how guest pages are used, which means that
SGX virtualization use of EREMOVE might fail. Specifically, it is
legitimate that EREMOVE returns SGX_CHILD_PRESENT for EPC assigned to
KVM guest, because KVM/kernel doesn't track SECS pages.

To allow SGX/KVM to introduce a more permissive EREMOVE helper and
to let the SGX virtualization code use the allocator directly, break
out the EREMOVE call from the SGX page allocator. Rename the original
sgx_free_epc_page() to sgx_encl_free_epc_page(), indicating that
it is used to free an EPC page assigned to a host enclave. Replace
sgx_free_epc_page() with sgx_encl_free_epc_page() in all call sites so
there's no functional change.

At the same time, improve the error message when EREMOVE fails, and
add documentation to explain to the user what that failure means and
to suggest to the user what to do when this bug happens in the case it
happens.

 [ bp: Massage commit message, fix typos and sanitize text, simplify. ]

Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lkml.kernel.org/r/20210325093057.122834-1-kai.huang@intel.com
2021-03-26 22:51:23 +01:00
..
i386 Documentation: x86: convert i386/IO-APIC.txt to reST 2019-05-08 14:34:11 -06:00
x86_64 A handful of late-arriving documentation fixes. 2020-10-23 17:13:53 -07:00
amd-memory-encryption.rst Documentation: x86: convert amd-memory-encryption.txt to reST 2019-05-08 14:34:10 -06:00
boot.rst Documentation/x86/boot.rst: Correct the example of SETUP_INDIRECT 2021-01-28 15:25:31 -07:00
booting-dt.rst dt: Remove booting-without-of.rst 2020-10-13 13:33:16 -05:00
cpuinfo.rst Documentation/x86: Add documentation for /proc/cpuinfo feature flags 2020-09-01 11:07:15 +02:00
earlyprintk.rst Documentation: x86: earlyprintk: drop doubled words 2020-07-13 09:47:38 -06:00
entry_64.rst Documentation: x86: convert entry_64.txt to reST 2019-05-08 14:34:09 -06:00
exception-tables.rst Merge branch 'x86-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2020-03-31 11:04:05 -07:00
features.rst docs: archis: add a per-architecture features list 2020-12-03 15:10:15 -07:00
index.rst A much quieter cycle for documentation (happily), with, one hopes, the bulk 2020-12-14 16:55:54 -08:00
intel_txt.rst docs: x86: move two x86-specific files to x86 arch dir 2019-07-15 11:03:01 -03:00
intel-iommu.rst docs: prevent warnings due to autosectionlabel 2020-03-20 17:01:29 -06:00
kernel-stacks.rst Some late arriving documentation changes. In particular, this contains the 2019-05-10 13:24:53 -04:00
mds.rst x86/speculation/mds: Improve CPU buffer clear documentation 2019-05-16 09:05:12 +02:00
microcode.rst Documentation: x86: convert microcode.txt to reST 2019-05-08 14:34:11 -06:00
mtrr.rst Documentation: x86: convert mtrr.txt to reST 2019-05-08 14:34:10 -06:00
orc-unwinder.rst Documentation: x86: convert orc-unwinder.txt to reST 2019-05-08 14:34:11 -06:00
pat.rst remove ioremap_nocache and devm_ioremap_nocache 2020-01-06 09:45:59 +01:00
pti.rst Documentation: x86: convert pti.txt to reST 2019-05-08 14:34:10 -06:00
resctrl.rst Documentation/x86: Rename resctrl_ui.rst and add two errata to the file 2020-10-27 16:47:00 +01:00
sgx.rst x86/sgx: Wipe out EREMOVE from sgx_free_epc_page() 2021-03-26 22:51:23 +01:00
sva.rst Documentation/x86: Add documentation for SVA (Shared Virtual Addressing) 2020-09-17 19:29:42 +02:00
tlb.rst Documentation: x86: convert tlb.txt to reST 2019-05-08 14:34:10 -06:00
topology.rst x86/CPU/AMD: Save AMD NodeId as cpu_die_id 2020-11-19 11:43:13 +01:00
tsx_async_abort.rst x86/speculation/taa: Add documentation for TSX Async Abort 2019-10-28 08:37:00 +01:00
usb-legacy-support.rst Documentation: x86: convert usb-legacy-support.txt to reST 2019-05-08 14:34:11 -06:00
zero-page.rst Documentation: x86: convert zero-page.txt to reST 2019-05-08 14:34:10 -06:00