On 27/01/21 02:25, Kai Huang wrote:
On Tue, 26 Jan 2021 08:04:35 -0800 Dave Hansen wrote:
On 1/26/21 1:30 AM, Kai Huang wrote:
From: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
Encapsulate the snippet in sgx_free_epc_page() concerning EREMOVE to
sgx_reset_epc_page(), which is a static helper function for
sgx_encl_release(). It's the only function existing, which deals with
initialized pages.
Yikes. I have no idea what that is saying. Here's a rewrite:
EREMOVE takes a pages 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.
KVM does not track how guest pages are used, which means that SGX
virtualization use of EREMOVE might fail.
Break out the EREMOVE call from the SGX page allocator. This will allow
the SGX virtualization code to use the allocator directly. (SGX/KVM
will also introduce a more permissive EREMOVE helper).
Thanks.
Hi Jarkko,
Do you want me to update your patch directly, or do you want to take the
change, and send me the patch again?
I think you should treat all these 27 patches as yours now (including
removing them, reordering them, adjusting commit message etc.).
OK, so if you're going to say "the caller must put the page in
uninitialized state", let's also add a comment to the place that *DO*
that, like the shiny new sgx_reset_epc_page().
Hi Dave,
Sorry I am a little bit confused here. Do you mean we should add a comment in
sgx_reset_epc_page() to say, for instance: sgx_free_epc_page() requires the EPC
page already been EREMOVE'd?
I also don't understand Dave's comment. I would say
It's the caller's responsibility to make sure that the page is in
uninitialized state with EREMOVE (sgx_reset_epc_page), EWB etc. before
calling this function.
Paolo
