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Date: Mon, 13 Sep 2021 16:24:39 +0200 From: Paolo Bonzini <pbonzini@...hat.com> To: Dave Hansen <dave.hansen@...el.com>, linux-kernel@...r.kernel.org, kvm@...r.kernel.org Cc: x86@...nel.org, linux-sgx@...r.kernel.org, jarkko@...nel.org, dave.hansen@...ux.intel.com, yang.zhong@...el.com Subject: Re: [PATCH 1/2] x86: sgx_vepc: extract sgx_vepc_remove_page On 13/09/21 16:05, Dave Hansen wrote: > On 9/13/21 6:11 AM, Paolo Bonzini wrote: >> Windows expects all pages to be in uninitialized state on startup. >> In order to implement this, we will need a ioctl that performs >> EREMOVE on all pages mapped by a /dev/sgx_vepc file descriptor: >> other possibilities, such as closing and reopening the device, >> are racy. > > Hi Paolo, > > How does this end up happening in the first place? > > All enclave pages should start out on 'sgx_dirty_page_list' and > ksgxd sanitizes them with EREMOVE before making them available. That > should cover EREMOVE after reboots while SGX pages are initialized, > including kexec(). By "Windows startup" I mean even after guest reboot. Because another process could sneak in and steal your EPC pages between a close() and an open(), I'd like to have a way to EREMOVE the pages while keeping them assigned to the specific vEPC instance, i.e. *without* going through sgx_vepc_free_page(). Thanks, Paolo > sgx_vepc_free_page() should do the same for pages that a guest not not > clean up properly. > > sgx_encl_free_epc_page() does an EREMOVE after a normal enclave has used > a page. > > Those are the only three cases that I can think of. So, it sounds like > one of those is buggy, or there's another unexpected path out there. > Ultimately, I think it would be really handy if we could do this EREMOVE > implicitly and without any new ABI. >
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