From: Paolo Bonzini <pbonzini@redhat.com>
To: Jarkko Sakkinen <jarkko@kernel.org>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: x86@kernel.org, linux-sgx@vger.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: Thu, 23 Sep 2021 14:08:56 +0200 [thread overview]
Message-ID: <a0a2a628-62c5-d620-7714-2c28e4429e71@redhat.com> (raw)
In-Reply-To: <060cfbbaa2c7a1a0643584aa79e6d6f3ab7c8f64.camel@kernel.org>
On 21/09/21 21:44, Jarkko Sakkinen wrote:
> "On bare-metal SGX, start of a power cycle zeros all of its reserved
> memory. This happens after every reboot, but in addition to that
> happens after waking up from any of the sleep states."
>
> I can speculate and imagine where this might useful, but no matter
> how trivial or complex it is, this patch needs to nail a concrete
> usage example. I'd presume you know well the exact changes needed for
> QEMU, so from that knowledge it should be easy to write the
> motivational part.
Assuming that it's obvious that QEMU knows how to reset a machine (which
includes writes to the ACPI reset register, or wakeup from sleep
states), the question of "why does userspace reuse vEPC" should be
answered by this paragraph:
"One way to do this is to simply close and reopen the /dev/sgx_vepc file
descriptor and re-mmap the virtual EPC. However, this is problematic
because it prevents sandboxing the userspace (for example forbidding
open() after the guest starts, or running in a mount namespace that
does not have access to /dev; both are doable with pre-opened file
descriptors and/or SCM_RIGHTS file descriptor passing)."
> Even to a Linux guest, since EPC should stil be represented in the
> state that matches the hardware. It'd be essentially a corrupted
> state, even if there was measures to resist this. Windows guests
> failing is essentially a side-effect of an issue, not an issue in the
> Windows guests.
Right, Linux is more liberal than it needs to be and ksgxd does the
EREMOVE itself at the beginning (__sgx_sanitize_pages). Windows has
stronger expectations of what can and cannot happen before it boots,
which are entirely justified.
Paolo
next prev parent reply other threads:[~2021-09-23 12:09 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-20 12:53 [PATCH 0/2] x86: sgx_vepc: implement ioctl to EREMOVE all pages 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 [this message]
2021-09-23 20:33 ` Jarkko Sakkinen
2021-09-20 12:54 ` [PATCH 2/2] x86: sgx_vepc: implement SGX_IOC_VEPC_REMOVE_ALL ioctl Paolo Bonzini
2021-09-20 22:17 ` Kai Huang
2021-09-20 23:09 ` Dave Hansen
2021-09-21 10:29 ` Paolo Bonzini
-- strict thread matches above, loose matches on Subject: below --
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
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
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