linux-kernel - Re: [PATCH 05/25] x86/sgx: Introduce virtual EPC for use by KVM guests

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Message-ID: <YD0Uf1LS4jDlXGLo@google.com>
Date:   Mon, 1 Mar 2021 08:21:19 -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 05/25] x86/sgx: Introduce virtual EPC for use by KVM
 guests

On Mon, Mar 01, 2021, Kai Huang wrote:
> +	/*
> +	 * SECS pages are "pinned" by child pages, an unpinned once all

s/an/and

> +	 * children have been EREMOVE'd.  A child page in this instance
> +	 * may have pinned an SECS page encountered in an earlier release(),
> +	 * creating a zombie.  Since some children were EREMOVE'd above,
> +	 * try to EREMOVE all zombies in the hopes that one was unpinned.
> +	 */
> +	mutex_lock(&zombie_secs_pages_lock);
> +	list_for_each_entry_safe(epc_page, tmp, &zombie_secs_pages, list) {
> +		/*
> +		 * Speculatively remove the page from the list of zombies,
> +		 * if the page is successfully EREMOVE it will be added to
> +		 * the list of free pages.  If EREMOVE fails, throw the page
> +		 * on the local list, which will be spliced on at the end.
> +		 */
> +		list_del(&epc_page->list);
> +
> +		if (sgx_vepc_free_page(epc_page))
> +			list_add_tail(&epc_page->list, &secs_pages);
> +	}
> +
> +	if (!list_empty(&secs_pages))
> +		list_splice_tail(&secs_pages, &zombie_secs_pages);
> +	mutex_unlock(&zombie_secs_pages_lock);
> +
> +	kfree(vepc);
> +
> +	return 0;
> +}