From: Kai Huang <kai.huang@intel.com>
To: Sean Christopherson <seanjc@google.com>,
Dave Hansen <dave.hansen@intel.com>
Cc: linux-sgx@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org,
jarkko@kernel.org, luto@kernel.org, rick.p.edgecombe@intel.com,
haitao.huang@intel.com, pbonzini@redhat.com, bp@alien8.de,
tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com
Subject: Re: [RFC PATCH v4 04/26] x86/sgx: Add SGX_CHILD_PRESENT hardware error code
Date: Wed, 10 Feb 2021 10:03:02 +1300 [thread overview]
Message-ID: <ddc22787d6d4abf51c47b28ec6fe6df85d0fea3e.camel@intel.com> (raw)
In-Reply-To: <YCLBQYq2HaA7MFKH@google.com>
On Tue, 2021-02-09 at 17:07 +0000, Sean Christopherson wrote:
> On Tue, Feb 09, 2021, Dave Hansen wrote:
> > On 2/9/21 8:48 AM, Sean Christopherson wrote:
> > > On Tue, Feb 09, 2021, Dave Hansen wrote:
> > > > On 2/8/21 2:54 AM, Kai Huang wrote:
> > > > ...
> > > > > Add SGX_CHILD_PRESENT for use by SGX virtualization to assert EREMOVE
> > > > > failures are expected, but only due to SGX_CHILD_PRESENT.
> > > > This paragraph broke my brain when I read it. How about:
> > > >
> > > > Add a definition of SGX_CHILD_PRESENT. It will be used
> > > > exclusively by the SGX virtualization driver to suppress EREMOVE
> > > > warnings.
> > > Maybe worth clarifying that the driver isn't suppressing warnings willy-nilly?
> > > And the error code isn't about suppressing warnings, it's about identifying the
> > > expected EREMOVE failure scenario. The patch that creates the separate helper
> > > for doing EREMOVE without the WARN is what provides the suppression mechanism.
> > >
> > > Something like this?
> > >
> > > Add a definition of SGX_CHILD_PRESENT. It will be used exclusively by
> > > the SGX virtualization driver to handle recoverable EREMOVE errors when
> > > saniziting EPC pages after they are reclaimed from a guest.
> >
> > Looks great to me. One nit: to a me, "reclaim" is different than
> > "free". Reclaim is a specific operation where a page is taken from one
> > user and reclaimed for other use. "Free" is the more general case
> > (which includes reclaim) when a physical page is no longer being used
> > (because the user is done *or* had the page reclaimed) and may be either
> > used by someone else or put in a free pool.
> >
> > I *think* this is actually a "free" operation, rather than a "reclaim".
> > IIRC, this code gets used at munmap().
>
> It does. I used reclaim because userspace, which does the freeing from this
> code's perspective, never touches the EPC pages. The SGX_CHILD_PRESENT case is
> handling the scenario where userspace has for all intents and purposed reclaimed
> the EPC from a guest. If the guest cleanly tears down its enclaves, EREMOVE
> will not fail.
>
> "free" is probably better though, the above is far from obvious and still not
> guaranteed to be a true reclaim scenario. If using "freed", drop the "from a
> guest" part.
Thanks for feedback. I'll use below:
Add a definition of SGX_CHILD_PRESENT. It will be used exclusively by
the SGX virtualization driver to handle recoverable EREMOVE errors when
saniziting EPC pages after they are freed.
next prev parent reply other threads:[~2021-02-09 21:50 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-08 10:53 [RFC PATCH v4 00/26] KVM SGX virtualization support Kai Huang
2021-02-08 10:54 ` [RFC PATCH v4 01/26] x86/cpufeatures: Make SGX_LC feature bit depend on SGX bit Kai Huang
2021-02-08 10:54 ` [RFC PATCH v4 02/26] x86/cpufeatures: Add SGX1 and SGX2 sub-features Kai Huang
2021-02-09 16:11 ` Dave Hansen
2021-02-08 10:54 ` [RFC PATCH v4 03/26] x86/sgx: Wipe out EREMOVE from sgx_free_epc_page() Kai Huang
2021-02-09 16:18 ` Dave Hansen
2021-02-09 18:26 ` Kai Huang
2021-02-08 10:54 ` [RFC PATCH v4 04/26] x86/sgx: Add SGX_CHILD_PRESENT hardware error code Kai Huang
2021-02-09 16:24 ` Dave Hansen
2021-02-09 16:48 ` Sean Christopherson
2021-02-09 16:52 ` Dave Hansen
2021-02-09 17:07 ` Sean Christopherson
2021-02-09 21:03 ` Kai Huang [this message]
2021-02-08 10:54 ` [RFC PATCH v4 05/26] x86/sgx: Introduce virtual EPC for use by KVM guests Kai Huang
2021-02-09 21:18 ` Jarkko Sakkinen
2021-02-09 21:19 ` Jarkko Sakkinen
2021-02-09 21:36 ` Dave Hansen
2021-02-10 0:20 ` Kai Huang
2021-02-10 16:52 ` Sean Christopherson
2021-02-10 23:12 ` Kai Huang
2021-02-12 12:17 ` [RFC PATCH v4 05/26] x86/sgx: Introduce virtual EPC for use by KVM guests' Jarkko Sakkinen
2021-02-13 13:33 ` Kai Huang
2021-02-12 12:15 ` [RFC PATCH v4 05/26] x86/sgx: Introduce virtual EPC for use by KVM guests Jarkko Sakkinen
2021-02-12 12:14 ` Jarkko Sakkinen
2021-02-08 10:54 ` [RFC PATCH v4 06/26] x86/cpu/intel: Allow SGX virtualization without Launch Control support Kai Huang
2021-02-08 10:54 ` [RFC PATCH v4 07/26] x86/sgx: Initialize virtual EPC driver even when SGX driver is disabled Kai Huang
2021-02-08 10:54 ` [RFC PATCH v4 08/26] x86/sgx: Expose SGX architectural definitions to the kernel Kai Huang
2021-02-08 10:54 ` [RFC PATCH v4 09/26] x86/sgx: Move ENCLS leaf definitions to sgx_arch.h Kai Huang
2021-02-08 10:54 ` [RFC PATCH v4 10/26] x86/sgx: Add SGX2 ENCLS leaf definitions (EAUG, EMODPR and EMODT) Kai Huang
2021-02-08 10:54 ` [RFC PATCH v4 11/26] x86/sgx: Add encls_faulted() helper Kai Huang
2021-02-08 10:54 ` [RFC PATCH v4 12/26] x86/sgx: Add helper to update SGX_LEPUBKEYHASHn MSRs Kai Huang
2021-02-08 10:54 ` [RFC PATCH v4 13/26] x86/sgx: Add helpers to expose ECREATE and EINIT to KVM Kai Huang
2021-02-08 10:54 ` [RFC PATCH v4 14/26] x86/sgx: Move provisioning device creation out of SGX driver Kai Huang
2021-02-08 10:55 ` [RFC PATCH v4 15/26] KVM: VMX: Convert vcpu_vmx.exit_reason to a union Kai Huang
2021-02-08 11:11 ` Kai Huang
2021-02-08 14:39 ` Xiaoyao Li
2021-02-09 0:09 ` Kai Huang
2021-02-08 10:55 ` [RFC PATCH v4 16/26] KVM: x86: Export kvm_mmu_gva_to_gpa_{read,write}() for SGX (VMX) Kai Huang
2021-02-08 10:55 ` [RFC PATCH v4 17/26] KVM: x86: Define new #PF SGX error code bit Kai Huang
2021-02-08 10:55 ` [RFC PATCH v4 18/26] KVM: x86: Add support for reverse CPUID lookup of scattered features Kai Huang
2021-02-08 11:05 ` Kai Huang
2021-02-08 10:55 ` [RFC PATCH v4 19/26] KVM: x86: Add reverse-CPUID lookup support for scattered SGX features Kai Huang
2021-02-08 10:55 ` [RFC PATCH v4 20/26] KVM: VMX: Add basic handling of VM-Exit from SGX enclave Kai Huang
2021-02-08 10:55 ` [RFC PATCH v4 21/26] KVM: VMX: Frame in ENCLS handler for SGX virtualization Kai Huang
2021-02-08 10:55 ` [RFC PATCH v4 22/26] KVM: VMX: Add SGX ENCLS[ECREATE] handler to enforce CPUID restrictions Kai Huang
2021-02-08 10:55 ` [RFC PATCH v4 23/26] KVM: VMX: Add emulation of SGX Launch Control LE hash MSRs Kai Huang
2021-02-08 10:55 ` [RFC PATCH v4 24/26] KVM: VMX: Add ENCLS[EINIT] handler to support SGX Launch Control (LC) Kai Huang
2021-02-08 10:55 ` [RFC PATCH v4 25/26] KVM: VMX: Enable SGX virtualization for SGX1, SGX2 and LC Kai Huang
2021-02-08 10:56 ` [RFC PATCH v4 26/26] KVM: x86: Add capability to grant VM access to privileged SGX attribute Kai Huang
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