From: Paolo Bonzini <pbonzini@redhat.com>
To: Dave Hansen <dave.hansen@intel.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: x86@kernel.org, linux-sgx@vger.kernel.org, jarkko@kernel.org,
dave.hansen@linux.intel.com, yang.zhong@intel.com
Subject: Re: [PATCH 1/2] x86: sgx_vepc: extract sgx_vepc_remove_page
Date: Mon, 13 Sep 2021 20:35:53 +0200 [thread overview]
Message-ID: <2b595588-eb98-6d30-dc50-794fc396bf7e@redhat.com> (raw)
In-Reply-To: <480cf917-7301-4227-e1c4-728b52537f46@intel.com>
On 13/09/21 17:29, Dave Hansen wrote:
> On 9/13/21 8:14 AM, Paolo Bonzini wrote:
>> On 13/09/21 16:55, Dave Hansen wrote:
>>>> 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().
>>> Oh, so you want fresh EPC state for the guest, but you're concerned that
>>> the previous guest might have left them in a bad state. The current
>>> method of getting a new vepc instance (which guarantees fresh state) has
>>> some other downsides.
>>>
>>> Can't another process steal pages via sgxd and reclaim at any time?
>>
>> vEPC pages never call sgx_mark_page_reclaimable, don't they?
>
> Oh, I was just looking that they were on the SGX LRU. You might be right.
> But, we certainly don't want the fact that they are unreclaimable today
> to be part of the ABI. It's more of a bug than a feature.
Sure, that's fine.
>>> What's the extra concern here about going through a close()/open()
>>> cycle? Performance?
>>
>> Apart from reclaiming, /dev/sgx_vepc might disappear between the first
>> open() and subsequent ones.
>
> Aside from it being rm'd, I don't think that's possible.
>
Being rm'd would be a possibility in principle, and it would be ugly for
it to cause issues on running VMs. Also I'd like for it to be able to
pass /dev/sgx_vepc in via a file descriptor, and run QEMU in a chroot or
a mount namespace. Alternatively, with seccomp it may be possible to
sandbox a running QEMU process in such a way that open() is forbidden at
runtime (all hotplug is done via file descriptor passing); it is not yet
possible, but it is a goal.
Paolo
next prev parent reply other threads:[~2021-09-13 18:36 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-13 13:11 [RFC/RFT PATCH 0/2] x86: sgx_vepc: implement ioctl to EREMOVE all pages Paolo Bonzini
2021-09-13 13:11 ` [PATCH 1/2] x86: sgx_vepc: extract sgx_vepc_remove_page Paolo Bonzini
2021-09-13 14:05 ` Dave Hansen
2021-09-13 14:24 ` Paolo Bonzini
2021-09-13 14:55 ` Dave Hansen
2021-09-13 15:14 ` Paolo Bonzini
2021-09-13 15:29 ` Dave Hansen
2021-09-13 18:35 ` Paolo Bonzini [this message]
2021-09-13 19:25 ` Dave Hansen
2021-09-13 21:16 ` Jarkko Sakkinen
2021-09-13 21:15 ` Jarkko Sakkinen
2021-09-13 21:13 ` Jarkko Sakkinen
2021-09-14 5:36 ` Paolo Bonzini
2021-09-14 16:05 ` Jarkko Sakkinen
2021-09-13 21:12 ` Jarkko Sakkinen
2021-09-13 21:00 ` Jarkko Sakkinen
2021-09-13 20:33 ` Jarkko Sakkinen
2021-09-13 13:11 ` [PATCH 2/2] x86: sgx_vepc: implement SGX_IOC_VEPC_REMOVE ioctl Paolo Bonzini
2021-09-13 19:33 ` Dave Hansen
2021-09-13 21:11 ` Sean Christopherson
2021-09-13 22:43 ` Dave Hansen
2021-09-14 10:55 ` Kai Huang
2021-09-14 7:10 ` [RFC/RFT PATCH 0/2] x86: sgx_vepc: implement ioctl to EREMOVE all pages Yang Zhong
2021-09-14 10:19 ` Paolo Bonzini
2021-09-14 16:42 ` Jarkko Sakkinen
2021-09-14 17:07 ` Paolo Bonzini
2021-09-14 17:40 ` Jarkko Sakkinen
2021-09-14 17:44 ` Jarkko Sakkinen
2021-09-15 8:28 ` Yang Zhong
-- strict thread matches above, loose matches on Subject: below --
2021-09-20 12:53 [PATCH " Paolo Bonzini
2021-09-20 12:54 ` [PATCH 1/2] x86: sgx_vepc: extract sgx_vepc_remove_page Paolo Bonzini
2021-09-21 19:44 ` Jarkko Sakkinen
2021-09-21 19:46 ` Jarkko Sakkinen
2021-09-23 12:08 ` Paolo Bonzini
2021-09-23 20:33 ` Jarkko Sakkinen
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