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From: Kai Huang <kai.huang@intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
	linux-sgx@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org,
	jarkko@kernel.org, luto@kernel.org, haitao.huang@intel.com,
	pbonzini@redhat.com, bp@alien8.de, tglx@linutronix.de,
	mingo@redhat.com, hpa@zytor.com
Subject: Re: [RFC PATCH 03/23] x86/sgx: Introduce virtual EPC for use by KVM guests
Date: Thu, 7 Jan 2021 13:47:58 +1300	[thread overview]
Message-ID: <20210107134758.ba0b5d950282973eaefe1ded@intel.com> (raw)
In-Reply-To: <X/YfE28guNBxcpui@google.com>


> > > +static struct mutex virt_epc_lock;
> > > +static struct list_head virt_epc_zombie_pages;
> > 
> > What does the lock protect?
> 
> Effectively, the list of zombie SECS pages.  Not sure why I used a generic name.
> 
> > What are zombie pages?
> 
> My own terminology for SECS pages whose virtual EPC has been destroyed but can't
> be reclaimed due to them having child EPC pages in other virtual EPCs.
> 
> > BTW, if zombies are SECS-only, shouldn't that be in the name rather than
> > "epc"?
> 
> I used the virt_epc prefix/namespace to tag it as a global list.  I've no
> argument against something like zombie_secs_pages.

I'll change to zombie_secs_pages, and lock name to zombie_secs_pages_lock,
respectively.


[...]

> > > +static int sgx_virt_epc_free_page(struct sgx_epc_page *epc_page)
> > > +{
> > > +	int ret;
> > > +
> > > +	if (!epc_page)
> > > +		return 0;
> > 
> > I always worry about these.  Why is passing NULL around OK?
> 
> I suspect I did it to mimic kfree() behavior.  I don't _think_ the radix (now
> xarray) usage will ever encounter a NULL entry.

I'll remove the NULL page check.

> 
> > 
> > > +	ret = __eremove(sgx_get_epc_virt_addr(epc_page));
> > > +	if (ret) {
> > > +		/*
> > > +		 * Only SGX_CHILD_PRESENT is expected, which is because of
> > > +		 * EREMOVE-ing an SECS still with child, in which case it can
> > > +		 * be handled by EREMOVE-ing the SECS again after all pages in
> > > +		 * virtual EPC have been EREMOVE-ed. See comments in below in
> > > +		 * sgx_virt_epc_release().
> > > +		 */
> > > +		WARN_ON_ONCE(ret != SGX_CHILD_PRESENT);
> > > +		return ret;
> > > +	}
> > 
> > I find myself wondering what errors could cause the WARN_ON_ONCE() to be
> > hit.  The SDM indicates that it's only:
> > 
> > 	SGX_ENCLAVE_ACT If there are still logical processors executing
> > 			inside the enclave.
> > 
> > Should that be mentioned in the comment?
> 
> And faults, which are also spliced into the return value by the ENCLS macros.
> I do remember hitting this WARN when I broke things, though I can't remember
> whether it was a fault or the SGX_ENCLAVE_ACT scenario.  Probably the latter?

I'll add a comment saying that there should be no active logical processor
still running inside guest's enclave. We cannot handle SGX_ENCLAVE_ACT here
anyway.

  reply	other threads:[~2021-01-07  0:48 UTC|newest]

Thread overview: 111+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-06  1:55 [RFC PATCH 00/23] KVM SGX virtualization support Kai Huang
2021-01-06  1:55 ` [RFC PATCH 01/23] x86/sgx: Split out adding EPC page to free list to separate helper Kai Huang
2021-01-11 22:38   ` Jarkko Sakkinen
2021-01-12  0:19     ` Kai Huang
2021-01-12 21:45       ` Sean Christopherson
2021-01-13  1:15         ` Kai Huang
2021-01-13 17:05         ` Jarkko Sakkinen
2021-01-06  1:55 ` [RFC PATCH 02/23] x86/sgx: Add enum for SGX_CHILD_PRESENT error code Kai Huang
2021-01-06 18:28   ` Dave Hansen
2021-01-06 21:40     ` Kai Huang
2021-01-12  0:26     ` Jarkko Sakkinen
2021-01-11 23:32   ` Jarkko Sakkinen
2021-01-12  0:16     ` Kai Huang
2021-01-12  1:46       ` Jarkko Sakkinen
2021-01-06  1:55 ` [RFC PATCH 03/23] x86/sgx: Introduce virtual EPC for use by KVM guests Kai Huang
2021-01-06 19:35   ` Dave Hansen
2021-01-06 20:35     ` Sean Christopherson
2021-01-07  0:47       ` Kai Huang [this message]
2021-01-07  0:52         ` Dave Hansen
2021-01-07  1:38           ` Kai Huang
2021-01-07  5:00             ` Dave Hansen
2021-01-07  1:42     ` Kai Huang
2021-01-07  5:02       ` Dave Hansen
2021-01-15 14:07         ` Kai Huang
2021-01-15 15:39           ` Dave Hansen
2021-01-15 21:33             ` Kai Huang
2021-01-15 21:45               ` Sean Christopherson
2021-01-15 22:30                 ` Kai Huang
2021-01-11 23:38   ` Jarkko Sakkinen
2021-01-12  0:56     ` Kai Huang
2021-01-12  1:50       ` Jarkko Sakkinen
2021-01-12  2:03         ` Kai Huang
2021-01-06  1:55 ` [RFC PATCH 04/23] x86/cpufeatures: Add SGX1 and SGX2 sub-features Kai Huang
2021-01-06 19:39   ` Dave Hansen
2021-01-06 22:12     ` Kai Huang
2021-01-06 22:21       ` Dave Hansen
2021-01-06 22:56         ` Kai Huang
2021-01-06 23:19           ` Sean Christopherson
2021-01-06 23:33             ` Dave Hansen
2021-01-06 23:56             ` Kai Huang
2021-01-06 23:40         ` Kai Huang
2021-01-06 23:43           ` Dave Hansen
2021-01-06 23:56             ` Kai Huang
2021-01-06 22:15   ` Borislav Petkov
2021-01-06 23:09     ` Kai Huang
2021-01-07  6:41       ` Borislav Petkov
2021-01-08  2:00         ` Kai Huang
2021-01-08  5:10           ` Dave Hansen
2021-01-08  7:03             ` Kai Huang
2021-01-08  7:17               ` Borislav Petkov
2021-01-08  8:06                 ` Kai Huang
2021-01-08  8:13                   ` Borislav Petkov
2021-01-08  9:00                     ` Kai Huang
2021-01-08 23:55                 ` Sean Christopherson
2021-01-09  0:35                   ` Borislav Petkov
2021-01-09  1:01                     ` Sean Christopherson
2021-01-09  1:19                   ` Borislav Petkov
2021-01-11 17:54                     ` Sean Christopherson
2021-01-11 19:09                       ` Borislav Petkov
2021-01-11 19:20                         ` Sean Christopherson
2021-01-12  2:01                           ` Kai Huang
2021-01-12 12:13                           ` Borislav Petkov
2021-01-12 17:15                             ` Sean Christopherson
2021-01-12 17:51                               ` Borislav Petkov
2021-01-12 21:07                                 ` Kai Huang
2021-01-12 23:17                                   ` Sean Christopherson
2021-01-13  1:05                                     ` Kai Huang
2021-01-11 23:39   ` Jarkko Sakkinen
2021-01-06  1:55 ` [RFC PATCH 05/23] x86/cpu/intel: Allow SGX virtualization without Launch Control support Kai Huang
2021-01-06 19:54   ` Dave Hansen
2021-01-06 22:34     ` Kai Huang
2021-01-06 22:38       ` Dave Hansen
2021-01-06  1:56 ` [RFC PATCH 06/23] x86/sgx: Expose SGX architectural definitions to the kernel Kai Huang
2021-01-06  1:56 ` [RFC PATCH 07/23] x86/sgx: Move ENCLS leaf definitions to sgx_arch.h Kai Huang
2021-01-06  1:56 ` [RFC PATCH 08/23] x86/sgx: Add SGX2 ENCLS leaf definitions (EAUG, EMODPR and EMODT) Kai Huang
2021-01-06  1:56 ` [RFC PATCH 09/23] x86/sgx: Add encls_faulted() helper Kai Huang
2021-01-06  1:56 ` [RFC PATCH 10/23] x86/sgx: Add helper to update SGX_LEPUBKEYHASHn MSRs Kai Huang
2021-01-06 19:56   ` Dave Hansen
2021-01-06  1:56 ` [RFC PATCH 11/23] x86/sgx: Add helpers to expose ECREATE and EINIT to KVM Kai Huang
2021-01-06 20:12   ` Dave Hansen
2021-01-06 21:04     ` Sean Christopherson
2021-01-06 21:23       ` Dave Hansen
2021-01-06 22:58         ` Kai Huang
2021-01-06  1:56 ` [RFC PATCH 12/23] x86/sgx: Move provisioning device creation out of SGX driver Kai Huang
2021-01-06  1:56 ` [RFC PATCH 13/23] KVM: VMX: Convert vcpu_vmx.exit_reason to a union Kai Huang
2021-01-06  1:56 ` [RFC PATCH 14/23] KVM: x86: Export kvm_mmu_gva_to_gpa_{read,write}() for SGX (VMX) Kai Huang
2021-01-06  1:56 ` [RFC PATCH 15/23] KVM: x86: Define new #PF SGX error code bit Kai Huang
2021-01-06  1:56 ` [RFC PATCH 16/23] KVM: x86: Add SGX feature leaf to reverse CPUID lookup Kai Huang
2021-01-06  1:56 ` [RFC PATCH 17/23] KVM: VMX: Add basic handling of VM-Exit from SGX enclave Kai Huang
2021-01-06  1:56 ` [RFC PATCH 18/23] KVM: VMX: Frame in ENCLS handler for SGX virtualization Kai Huang
2021-01-06  1:56 ` [RFC PATCH 19/23] KVM: VMX: Add SGX ENCLS[ECREATE] handler to enforce CPUID restrictions Kai Huang
2021-01-06  1:56 ` [RFC PATCH 20/23] KVM: VMX: Add emulation of SGX Launch Control LE hash MSRs Kai Huang
2021-01-06  1:56 ` [RFC PATCH 21/23] KVM: VMX: Add ENCLS[EINIT] handler to support SGX Launch Control (LC) Kai Huang
2021-01-06  1:56 ` [RFC PATCH 22/23] KVM: VMX: Enable SGX virtualization for SGX1, SGX2 and LC Kai Huang
2021-01-06  1:58 ` [RFC PATCH 23/23] KVM: x86: Add capability to grant VM access to privileged SGX attribute Kai Huang
2021-01-06  2:22 ` [RFC PATCH 00/23] KVM SGX virtualization support Kai Huang
2021-01-06 17:07 ` Dave Hansen
2021-01-07  0:34   ` Kai Huang
2021-01-07  0:48     ` Dave Hansen
2021-01-07  1:50       ` Kai Huang
2021-01-07 16:14         ` Sean Christopherson
2021-01-08  2:16           ` Kai Huang
2021-01-11 17:20 ` Jarkko Sakkinen
2021-01-11 18:37   ` Sean Christopherson
2021-01-12  1:58     ` Jarkko Sakkinen
2021-01-12  1:14   ` Kai Huang
2021-01-12  2:02     ` Jarkko Sakkinen
2021-01-12  2:07       ` Kai Huang
2021-01-15 14:43         ` Kai Huang
2021-01-16  9:31           ` Jarkko Sakkinen
2021-01-16  9:50             ` Jarkko Sakkinen

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