linux-kernel - Re: [PATCH v3 4/7] x86/sgx: Add SGX infrastructure to recover from poison

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Message-ID: <3534daf5-fae5-a85c-e198-c0b73e44ece4@intel.com>
Date:   Wed, 28 Jul 2021 15:29:31 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Tony Luck <tony.luck@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Jarkko Sakkinen <jarkko@...nel.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/7] x86/sgx: Add SGX infrastructure to recover from
 poison

On 7/28/21 1:46 PM, Tony Luck wrote:
> +int sgx_memory_failure(unsigned long pfn, int flags)
> +{
...
> +	page->flags |= SGX_EPC_PAGE_POISON;

Is this safe outside of any locks?

I see the reclaimer doing things like:

                epc_page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED;

I'd worry that this code and other non-atomic epc_page->flags
manipulation could trample on each other.

This might need to some some atomic bit manipulation *and* convert all
the other epc_page->flags users.