From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: linux-sgx@vger.kernel.org
Subject: Re: [PATCH for_v23 v3 12/12] x86/sgx: Reinstate per EPC section free page counts
Date: Fri, 18 Oct 2019 15:55:21 +0300 [thread overview]
Message-ID: <20191018125521.GD4027@linux.intel.com> (raw)
In-Reply-To: <20191018124942.GC4027@linux.intel.com>
On Fri, Oct 18, 2019 at 03:49:42PM +0300, Jarkko Sakkinen wrote:
> On Wed, Oct 16, 2019 at 11:37:45AM -0700, Sean Christopherson wrote:
> > Track the free page count on a per EPC section basis so that the value
> > is properly protected by the section's spinlock.
> >
> > As was pointed out when the change was proposed[*], using a global
> > non-atomic counter to track the number of free EPC pages is not safe.
> > The order of non-atomic reads and writes are not guaranteed, i.e.
> > concurrent RMW operats can write stale data. This causes a variety
> > of bad behavior, e.g. livelocks because the free page count wraps and
> > causes the swap thread to stop reclaiming.
> >
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
>
> What is the reason not change it just to atomic?
>
> For debugging the global is useful because it could be exposed
> as a sysfs file.
So the regression is that counter updates is read + store (was not btw
described in the commit message what the regression you are speaking
of, which means that I'm making a guess myself).
This means that changing the variable to atomic should be IMHO
sufficient.
/Jarkko
next prev parent reply other threads:[~2019-10-18 12:55 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-16 18:37 [PATCH for_v23 v3 00/12] x86/sgx: Bug fixes for v23 Sean Christopherson
2019-10-16 18:37 ` [PATCH for_v23 v3 01/12] x86/sgx: Pass EADD the kernel's virtual address for the source page Sean Christopherson
2019-10-18 9:57 ` Jarkko Sakkinen
2019-10-22 3:22 ` Sean Christopherson
2019-10-23 11:57 ` Jarkko Sakkinen
2019-10-16 18:37 ` [PATCH for_v23 v3 02/12] x86/sgx: Check the validity of the source page address for EADD Sean Christopherson
2019-10-16 18:37 ` [PATCH for_v23 v3 03/12] x86/sgx: Fix EEXTEND error handling Sean Christopherson
2019-10-18 10:42 ` Jarkko Sakkinen
2019-10-16 18:37 ` [PATCH for_v23 v3 04/12] x86/sgx: Drop mmap_sem before EEXTENDing an enclave page Sean Christopherson
2019-10-18 10:04 ` Jarkko Sakkinen
2019-10-16 18:37 ` [PATCH for_v23 v3 05/12] x86/sgx: Remove redundant message from WARN on non-emtpy mm_list Sean Christopherson
2019-10-18 12:08 ` Jarkko Sakkinen
2019-10-16 18:37 ` [PATCH for_v23 v3 06/12] x86/sgx: Fix a memory leak in sgx_encl_destroy() Sean Christopherson
2019-10-18 12:17 ` Jarkko Sakkinen
2019-10-16 18:37 ` [PATCH for_v23 v3 07/12] x86/sgx: WARN on any non-zero return from __eremove() Sean Christopherson
2019-10-16 18:37 ` [PATCH for_v23 v3 08/12] x86/sgx: WARN only once if EREMOVE fails Sean Christopherson
2019-10-16 18:37 ` [PATCH for_v23 v3 09/12] x86/sgx: Split second half of sgx_free_page() to a separate helper Sean Christopherson
2019-10-18 10:06 ` Jarkko Sakkinen
2019-10-22 3:36 ` Sean Christopherson
2019-10-23 11:59 ` Jarkko Sakkinen
2019-10-16 18:37 ` [PATCH for_v23 v3 10/12] x86/sgx: Use the post-reclaim variant of __sgx_free_page() Sean Christopherson
2019-10-16 18:37 ` [PATCH for_v23 v3 11/12] x86/sgx: Don't update free page count if EPC section allocation fails Sean Christopherson
2019-10-16 18:37 ` [PATCH for_v23 v3 12/12] x86/sgx: Reinstate per EPC section free page counts Sean Christopherson
2019-10-18 12:49 ` Jarkko Sakkinen
2019-10-18 12:55 ` Jarkko Sakkinen [this message]
2019-10-18 14:30 ` Sean Christopherson
2019-10-21 11:19 ` Jarkko Sakkinen
2019-10-22 19:35 ` Sean Christopherson
2019-10-23 12:02 ` Jarkko Sakkinen
2019-10-17 18:10 ` [PATCH for_v23 v3 00/12] x86/sgx: Bug fixes for v23 Jarkko Sakkinen
2019-10-17 18:12 ` Jarkko Sakkinen
2019-10-18 13:13 ` Jarkko Sakkinen
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