From: Isaku Yamahata <isaku.yamahata@gmail.com>
To: "Huang, Kai" <kai.huang@intel.com>
Cc: "isaku.yamahata@gmail.com" <isaku.yamahata@gmail.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
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Sean" <seanjc@google.com>,
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"Yamahata, Isaku" <isaku.yamahata@intel.com>,
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<kirill.shutemov@linux.intel.com>,
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<sathyanarayanan.kuppuswamy@linux.intel.com>,
"Huang, Ying" <ying.huang@intel.com>,
"Williams, Dan J" <dan.j.williams@intel.com>
Subject: Re: [PATCH v10 05/16] x86/virt/tdx: Add skeleton to enable TDX on demand
Date: Mon, 13 Mar 2023 21:02:00 -0700 [thread overview]
Message-ID: <20230314040200.GD3922605@ls.amr.corp.intel.com> (raw)
In-Reply-To: <a62497059fc3f31706a532b822d6c966bd981468.camel@intel.com>
On Tue, Mar 14, 2023 at 01:50:40AM +0000,
"Huang, Kai" <kai.huang@intel.com> wrote:
> On Mon, 2023-03-13 at 16:49 -0700, Isaku Yamahata wrote:
> > On Sun, Mar 12, 2023 at 11:08:44PM +0000,
> > "Huang, Kai" <kai.huang@intel.com> wrote:
> >
> > > On Wed, 2023-03-08 at 14:27 -0800, Isaku Yamahata wrote:
> > > > > +
> > > > > +static int try_init_module_global(void)
> > > > > +{
> > > > > + int ret;
> > > > > +
> > > > > + /*
> > > > > + * The TDX module global initialization only needs to be done
> > > > > + * once on any cpu.
> > > > > + */
> > > > > + spin_lock(&tdx_global_init_lock);
> > > > > +
> > > > > + if (tdx_global_init_status & TDX_GLOBAL_INIT_DONE) {
> > > > > + ret = tdx_global_init_status & TDX_GLOBAL_INIT_FAILED ?
> > > > > + -EINVAL : 0;
> > > > > + goto out;
> > > > > + }
> > > > > +
> > > > > + /* All '0's are just unused parameters. */
> > > > > + ret = seamcall(TDH_SYS_INIT, 0, 0, 0, 0, NULL, NULL);
> > > > > +
> > > > > + tdx_global_init_status = TDX_GLOBAL_INIT_DONE;
> > > > > + if (ret)
> > > > > + tdx_global_init_status |= TDX_GLOBAL_INIT_FAILED;
> > > >
> > > > If entropy is lacking (rdrand failure), TDH_SYS_INIT can return TDX_SYS_BUSY.
> > > > In such case, we should allow the caller to retry or make this function retry
> > > > instead of marking error stickily.
> > >
> > > The spec says:
> > >
> > > TDX_SYS_BUSY The operation was invoked when another TDX module
> > > operation was in progress. The operation may be retried.
> > >
> > > So I don't see how entropy is lacking is related to this error. Perhaps you
> > > were mixing up with KEY.CONFIG?
> >
> > TDH.SYS.INIT() initializes global canary value. TDX module is compiled with
> > strong stack protector enabled by clang and canary value needs to be
> > initialized. By default, the canary value is stored at
> > %fsbase:<STACK_CANARY_OFFSET 0x28>
> >
> > Although this is a job for libc or language runtime, TDX modules has to do it
> > itself because it's stand alone.
> >
> > From tdh_sys_init.c
> > _STATIC_INLINE_ api_error_type tdx_init_stack_canary(void)
> > {
> > ia32_rflags_t rflags = {.raw = 0};
> > uint64_t canary;
> > if (!ia32_rdrand(&rflags, &canary))
> > {
> > return TDX_SYS_BUSY;
> > }
> > ...
> > last_page_ptr->stack_canary.canary = canary;
> >
> >
>
> Then it is a hidden behaviour of the TDX module that is not reflected in the
> spec. I am not sure whether we should handle because:
>
> 1) This is an extremely rare case. Kernel would be basically under attack if
> such error happened. In the current series we don't handle such case in
> KEY.CONFIG either but just leave a comment (see patch 13).
>
> 2) Not sure whether this will be changed in the future.
>
> So I think we should keep as is.
TDX 1.5 spec introduced TDX_RND_NO_ENTROPY status code. For TDX 1.0, let's
postpone it to TDX 1.5 activity.
--
Isaku Yamahata <isaku.yamahata@gmail.com>
next prev parent reply other threads:[~2023-03-14 4:02 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-06 14:13 [PATCH v10 00/16] TDX host kernel support Kai Huang
2023-03-06 14:13 ` [PATCH v10 01/16] x86/tdx: Define TDX supported page sizes as macros Kai Huang
2023-03-16 12:37 ` David Hildenbrand
2023-03-16 22:41 ` Huang, Kai
2023-03-06 14:13 ` [PATCH v10 02/16] x86/virt/tdx: Detect TDX during kernel boot Kai Huang
2023-03-16 12:48 ` David Hildenbrand
2023-03-16 22:37 ` Huang, Kai
2023-03-23 17:02 ` David Hildenbrand
2023-03-23 22:15 ` Huang, Kai
2023-03-06 14:13 ` [PATCH v10 03/16] x86/virt/tdx: Make INTEL_TDX_HOST depend on X86_X2APIC Kai Huang
2023-03-16 12:57 ` David Hildenbrand
2023-03-06 14:13 ` [PATCH v10 04/16] x86/virt/tdx: Add SEAMCALL infrastructure Kai Huang
2023-03-06 14:13 ` [PATCH v10 05/16] x86/virt/tdx: Add skeleton to enable TDX on demand Kai Huang
2023-03-08 22:27 ` Isaku Yamahata
2023-03-12 23:08 ` Huang, Kai
2023-03-13 23:49 ` Isaku Yamahata
2023-03-14 1:50 ` Huang, Kai
2023-03-14 4:02 ` Isaku Yamahata [this message]
2023-03-14 5:45 ` Dave Hansen
2023-03-14 17:16 ` Isaku Yamahata
2023-03-14 17:38 ` Dave Hansen
2023-03-14 15:48 ` Dave Hansen
2023-03-15 11:10 ` Huang, Kai
2023-03-16 22:07 ` Huang, Kai
2023-03-23 13:49 ` Dave Hansen
2023-03-23 22:09 ` Huang, Kai
2023-03-23 22:12 ` Dave Hansen
2023-03-23 22:42 ` Huang, Kai
2023-03-16 0:31 ` Isaku Yamahata
2023-03-16 2:45 ` Isaku Yamahata
2023-03-16 2:52 ` Huang, Kai
2023-03-06 14:13 ` [PATCH v10 06/16] x86/virt/tdx: Get information about TDX module and TDX-capable memory Kai Huang
2023-03-06 14:13 ` [PATCH v10 07/16] x86/virt/tdx: Use all system memory when initializing TDX module as TDX memory Kai Huang
2023-03-09 1:38 ` Isaku Yamahata
2023-03-06 14:13 ` [PATCH v10 08/16] x86/virt/tdx: Add placeholder to construct TDMRs to cover all TDX memory regions Kai Huang
2023-03-06 14:13 ` [PATCH v10 09/16] x86/virt/tdx: Fill out " Kai Huang
2023-03-06 14:13 ` [PATCH v10 10/16] x86/virt/tdx: Allocate and set up PAMTs for TDMRs Kai Huang
2023-03-21 7:44 ` Dong, Eddie
2023-03-21 8:05 ` Huang, Kai
2023-03-06 14:13 ` [PATCH v10 11/16] x86/virt/tdx: Designate reserved areas for all TDMRs Kai Huang
2023-03-06 14:13 ` [PATCH v10 12/16] x86/virt/tdx: Configure TDX module with the TDMRs and global KeyID Kai Huang
2023-03-06 14:13 ` [PATCH v10 13/16] x86/virt/tdx: Configure global KeyID on all packages Kai Huang
2023-03-06 14:13 ` [PATCH v10 14/16] x86/virt/tdx: Initialize all TDMRs Kai Huang
2023-03-06 14:14 ` [PATCH v10 15/16] x86/virt/tdx: Flush cache in kexec() when TDX is enabled Kai Huang
2023-03-06 14:14 ` [PATCH v10 16/16] Documentation/x86: Add documentation for TDX host support Kai Huang
2023-03-08 1:11 ` [PATCH v10 00/16] TDX host kernel support Isaku Yamahata
2023-03-16 12:35 ` David Hildenbrand
2023-03-16 22:06 ` Huang, Kai
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