linux-kernel - Re: [PATCH v3 03/25] x86/sgx: Wipe out EREMOVE from sgx_free_epc

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Message-ID: <YEvbcrTZyiUAxZAu@google.com>
Date:   Fri, 12 Mar 2021 13:21:54 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Kai Huang <kai.huang@...el.com>
Cc:     kvm@...r.kernel.org, x86@...nel.org, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org, jarkko@...nel.org, luto@...nel.org,
        dave.hansen@...el.com, rick.p.edgecombe@...el.com,
        haitao.huang@...el.com, pbonzini@...hat.com, bp@...en8.de,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com
Subject: Re: [PATCH v3 03/25] x86/sgx: Wipe out EREMOVE from
 sgx_free_epc_page()

On Thu, Mar 11, 2021, Kai Huang wrote:
> From: Jarkko Sakkinen <jarkko@...nel.org>
> 
> 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.
> 
> 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).
> 
> Implement original sgx_free_epc_page() as sgx_encl_free_epc_page() to be
> more specific that it is used to free EPC page assigned to one enclave.
> Print an error message when EREMOVE fails to explicitly call out EPC
> page is leaked, and requires machine reboot to get leaked pages back.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> Co-developed-by: Kai Huang <kai.huang@...el.com>
> Acked-by: Jarkko Sakkinen <jarkko@...nel.org>
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> ---
> v2->v3:
> 
>  - Fixed bug during copy/paste which results in SECS page and va pages are not
>    correctly freed in sgx_encl_release() (sorry for the mistake).
>  - Added Jarkko's Acked-by.

That Acked-by should either be dropped or moved above Co-developed-by to make
checkpatch happy.

Reviewed-by: Sean Christopherson <seanjc@...gle.com>