* Re: [RFC PATCH] mm/vmalloc: add vmalloc_decrypted() and vzalloc_decrypted()
From: Jason Gunthorpe @ 2026-06-15 12:09 UTC (permalink / raw)
To: Michael Kelley
Cc: Catalin Marinas, Christoph Hellwig, Kameron Carr,
akpm@linux-foundation.org, urezki@gmail.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, rppt@kernel.org,
linux-coco@lists.linux.dev, Suzuki K Poulose
In-Reply-To: <SN6PR02MB4157EC032AD55D182FBC1318D4182@SN6PR02MB4157.namprd02.prod.outlook.com>
On Fri, Jun 12, 2026 at 07:06:00PM +0000, Michael Kelley wrote:
> > I thought arches are either preserving the memory content or zeroing
> > it, you are saying some arch leaves it as garbage? I'd argue that's an
> > arch bug and they should clear it in their path.
>
> AMD SEV-SNP leaves the memory contents as garbage after an encryption
> or decryption state change. On the flip side, my understanding has been
> that TDX zeroes the memory (or at least has an option to do so) after
> such a state change, though a couple of AI chats say TDX also leaves
> garbage. To be sure, I'd have to run an experiment to check in a TDX
> guest on Hyper-V.
So there are many bugs then if the pre-zero is lost and you have to
zero it again. Even swiotlb doesn't reliably zero it's pools in the
right order under these rules, though alloc coherent does get it
right at least.
IMHO this is too sketchy to be usable and optimizing for AMD is not
the right call, IMHO.
> > Otherwise this sharp edge is not documented and we have many other
> > places getting it wrong, eg system_heap_allocate() doesn't re-zero the
> > memory after decrypting it.
>
> In the Hyper-V code that uses set_memory_decrypted()/encrypted(),
> there's always an explicit call to set the memory to zero afterwards.
Good for it, maybe next time improve the APIs :(
Even more compelling that hyper-v should be using the dma api..
Jason
^ permalink raw reply
* Re: [PATCH v14 10/44] arm64: RMI: Add support for SRO
From: Steven Price @ 2026-06-15 11:45 UTC (permalink / raw)
To: Dan Williams (nvidia), Gavin Shan, kvm, kvmarm
Cc: Catalin Marinas, Marc Zyngier, Will Deacon, James Morse,
Oliver Upton, Suzuki K Poulose, Zenghui Yu, linux-arm-kernel,
linux-kernel, Joey Gouly, Alexandru Elisei, Christoffer Dall,
Fuad Tabba, linux-coco, Ganapatrao Kulkarni, Shanker Donthineni,
Alper Gun, Aneesh Kumar K . V, Emi Kisanuki, Vishal Annapurve,
WeiLin.Chang, Lorenzo.Pieralisi2
In-Reply-To: <6a2c91398fad5_a003b10027@djbw-dev.notmuch>
Hi Dan,
On 13/06/2026 00:07, Dan Williams (nvidia) wrote:
> Steven Price wrote:
> [..]
>>> alloc_pages_exact() will fail if the requested size exceeds the maximal
>>> allowed
>>> size (1 << MAX_PAGE_ORDER). The maximal size is usually smaller than
>>> PUD_SIZE
>>> but PUD_SIZE is allowed by the RMM.
>>
>> This is an area where to be honest I'm really not sure what to do.
>> Technically the RMM is allowed to ask for a contiguous range of 512GB
>> pages (on a 4K system - larger with larger page sizes) - but clearly no
>> real OS is going to be able to provide anything like that.
>>
>> In practise we don't expect the RMM to do anything so crazy. It's not
>> really clear to be whether even 2MB (PMD_SIZE) is needed. But the spec
>> is written to be generic.
>>
>> So my current approach is to calculate the required size and pass it
>> into alloc_pages_exact(). For "stupidly large" values this will fail and
>> Linux just doesn't support an RMM which attempts this. If there is ever
>> a usecase which needs this then we'd need to find a different method of
>> providing the memory (most likely some form of carveout to avoid
>> fragmentation). But my view is we should wait for that usecase to be
>> identified first.
>
> Just some comparison comments as I am also going through the TDX patches
> which enable "Extension SEAMCALLs". These new SEAMCALLs are similar to
> the SRO mechanism [1].
Looks like at least at the moment it's much more one-way than the SRO
mechanism - there's no reclaim mechanism (yet).
> TDX asks for an upfront delegation of memory at init time using
> alloc_contig_pages() that is never returned until entire module is
> shutdown. alloc_contig_pages() is not subject to the MAX_ORDER limit,
> but not sure that alloc_contig_pages() is suitable for small+dynamic
> runtime memory add / release that SRO potentially wants to do?
Yeah I'm not sure quite what is best. I expect the RMM to only request
contiguous memory for very small allocations to use as hardware page
tables. It's an issue I'm trying to work through that the specification
doesn't provide any guidance for what sort of allocations the host
should expect to provide.
> Does SRO always balance the size of RMI_OP_MEM_REQ_DONATE with
> RMI_OP_MEM_REQ_RECLAIM, or might some donate requests be a one way
> donation like TDX? Just poking to see if there is a path to preallocate
> a pool vs the fine grained per-operation alloc/free.
The spec is unfortunately not prescriptive on this point. For an
operation which eventually fails, the expectation is that the RMM will
return all the memory that was provided (and exactly that memory). But
the specification doesn't actually require that.
The problem is that there are situations where a racing operation on
another CPU could trigger this to not happen. For example, a new page
table needs to be allocated to complete a map operation, but then a
racing operation on another CPU makes use of this page table (e.g due to
a map at a different address), the memory for the page table cannot be
returned even if the operation doesn't complete because it's in use from
the racing operation.
I don't believe the current RMM design will actually do this - but it's
not something we actually want to prevent in the spec.
Equally the expectation is that all the donated memory for a guest will
be returned when the guest is destroyed. But we don't have anything in
the spec to enforce this.
I don't particularly expect a pool to be that useful for the expected
memory allocation patterns as I expect SRO donations to be long lived.
We don't (yet at least) have a concept of donating memory just for
"scratch" memory during an operation. Although the SRO mechanism doesn't
rule that out.
Thanks,
Steve
^ permalink raw reply
* Re: [PATCH RFC 0/3] KVM: guest_memfd: folio migration for non-confidential VMs
From: Alexandru Elisei @ 2026-06-15 11:04 UTC (permalink / raw)
To: Shivank Garg
Cc: Matthew Wilcox (Oracle), Jan Kara, Andrew Morton, Vlastimil Babka,
Suren Baghdasaryan, Michal Hocko, Brendan Jackman,
Johannes Weiner, Zi Yan, David Hildenbrand, Matthew Brost,
Joshua Hahn, Rakie Kim, Byungchul Park, Gregory Price, Ying Huang,
Alistair Popple, Paolo Bonzini, Shuah Khan, Chao Peng,
Nikunj A Dadhania, Ira Weiny, Michael Roth, Pankaj Gupta,
Ackerley Tng, Fuad Tabba, Sean Christopherson, Vishal Annapurve,
Nikita Kalyazin, Patrick Roy, Pratik Sampat, Ashish Kalra,
linux-fsdevel, linux-coco, linux-mm, linux-kernel, kvm,
linux-kselftest
In-Reply-To: <ai_XK__RTXMCEcCG@raptor>
Hi,
On Mon, Jun 15, 2026 at 11:43:14AM +0100, Alexandru Elisei wrote:
> Hi,
>
> On Thu, Jun 11, 2026 at 01:05:07PM +0000, Shivank Garg wrote:
> > guest_memfd folios are currently marked unmovable, so the kernel cannot
> > perform NUMA-balancing, memory compaction, etc. This is unavoidable for
> > confidential VMs (SEV-SNP, TDX), since memory is encrypted and copying it
> > needs firmware assistance. However, for non-confidential VMs (like
> > Firecracker), we can migrate the folios.
> >
> > This series enables folio migration for non-confidential guest_memfd and
> > also lays the groundwork for migrating confidential guest_memfd later.
> > Once firmware-assisted copying support is available, those VMs can be
> > made movable, the confidential folio content can be copied separately,
> > and the destination folio marked with FOLIO_CONTENT_COPIED so
> > __migrate_folio() skips the host-side folio_mc_copy().
>
> I always thought that one of the nice things about using guest_memfd as a
> memory backend, as opposed to host userspace mappings, is that the host
> cannot unmap VM memory because of KSM, automatic NUMA balancing, hugepage
> collapse, compaction, etc, acting on the host userspace mapping of the
> VM memory, and outside of the VMM's or KVM's control.
>
> I think it would be useful to preserve this behaviour, even in the absence
> of confidential VMs (i.e, guest_memfd file descriptor created with
> GUEST_MEMFD_FLAG_MMAP).
Just to be clear, I was thinking that it might be useful for both
behaviours to exist (migratable and non-migratable) for non-confidential
VMs, and allow KVM or userspace to decide which they prefer for a
guest_memfd.
Thanks,
Alex
^ permalink raw reply
* Re: [PATCH v13 09/22] KVM: selftests: Expose functions to get default sregs values
From: Chenyi Qiang @ 2026-06-15 10:54 UTC (permalink / raw)
To: Binbin Wu, Lisa Wang
Cc: Andrew Jones, Ackerley Tng, Chao Gao, Dave Hansen, Erdem Aktas,
Ira Weiny, Isaku Yamahata, Kiryl Shutsemau, linux-kselftest,
Paolo Bonzini, Pratik R. Sampat, Reinette Chatre, Rick Edgecombe,
Roger Wang, Ryan Afranji, Sagi Shahar, Sean Christopherson,
Shuah Khan, Oliver Upton, Jeremiah McReynolds, kvm, linux-coco,
linux-kernel, x86
In-Reply-To: <434e7f9a-5f64-4488-bf9d-5be8c3f9eefe@linux.intel.com>
On 6/8/2026 2:39 PM, Binbin Wu wrote:
> On 5/22/2026 7:16 AM, Lisa Wang wrote:
>
> [...]
>
>> +
>> +static inline u64 kvm_get_default_cr4(void)
>> +{
>> + u64 cr4 = X86_CR4_PAE | X86_CR4_OSFXSR;
>> +
>> + if (kvm_cpu_has(X86_FEATURE_XSAVE))
>> + cr4 |= X86_CR4_OSXSAVE;
>> + return cr4;
>> +}
>> +
>
> [...]
>
>> @@ -647,16 +643,12 @@ static void vcpu_init_sregs(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
>> vcpu_sregs_get(vcpu, &sregs);
>>
>> sregs.idt.base = vm->arch.idt;
>> - sregs.idt.limit = NUM_INTERRUPTS * sizeof(struct idt_entry) - 1;
>> + sregs.idt.limit = kvm_get_default_idt_limit();
>> sregs.gdt.base = vm->arch.gdt;
>> - sregs.gdt.limit = getpagesize() - 1;
>> -
>> - sregs.cr0 = X86_CR0_PE | X86_CR0_NE | X86_CR0_PG;
>> - sregs.cr4 |= X86_CR4_PAE | X86_CR4_OSFXSR;
>> - if (kvm_cpu_has(X86_FEATURE_XSAVE))
>> - sregs.cr4 |= X86_CR4_OSXSAVE;
>> - if (vm->mmu.pgtable_levels == 5)
>> - sregs.cr4 |= X86_CR4_LA57;
>
> I guess the 5-level paging thing is dropped unexpectedly during rebase?
>
>
>> + sregs.gdt.limit = kvm_get_default_gdt_limit();
>>
>> + sregs.cr0 = kvm_get_default_cr0();
>> + sregs.cr4 |= kvm_get_default_cr4();
>> sregs.efer |= (EFER_LME | EFER_LMA | EFER_NX);
Also, sregs.efer |= kvm_get_default_efer() is dropped unexpectedly during rebase.
>>
>> kvm_seg_set_unusable(&sregs.ldt);
>>
>
^ permalink raw reply
* Re: [PATCH RFC 0/3] KVM: guest_memfd: folio migration for non-confidential VMs
From: Alexandru Elisei @ 2026-06-15 10:43 UTC (permalink / raw)
To: Shivank Garg
Cc: Matthew Wilcox (Oracle), Jan Kara, Andrew Morton, Vlastimil Babka,
Suren Baghdasaryan, Michal Hocko, Brendan Jackman,
Johannes Weiner, Zi Yan, David Hildenbrand, Matthew Brost,
Joshua Hahn, Rakie Kim, Byungchul Park, Gregory Price, Ying Huang,
Alistair Popple, Paolo Bonzini, Shuah Khan, Chao Peng,
Nikunj A Dadhania, Ira Weiny, Michael Roth, Pankaj Gupta,
Ackerley Tng, Fuad Tabba, Sean Christopherson, Vishal Annapurve,
Nikita Kalyazin, Patrick Roy, Pratik Sampat, Ashish Kalra,
linux-fsdevel, linux-coco, linux-mm, linux-kernel, kvm,
linux-kselftest
In-Reply-To: <20260611-shivank-gmem-migrate-v1-0-2d266bfc6f95@amd.com>
Hi,
On Thu, Jun 11, 2026 at 01:05:07PM +0000, Shivank Garg wrote:
> guest_memfd folios are currently marked unmovable, so the kernel cannot
> perform NUMA-balancing, memory compaction, etc. This is unavoidable for
> confidential VMs (SEV-SNP, TDX), since memory is encrypted and copying it
> needs firmware assistance. However, for non-confidential VMs (like
> Firecracker), we can migrate the folios.
>
> This series enables folio migration for non-confidential guest_memfd and
> also lays the groundwork for migrating confidential guest_memfd later.
> Once firmware-assisted copying support is available, those VMs can be
> made movable, the confidential folio content can be copied separately,
> and the destination folio marked with FOLIO_CONTENT_COPIED so
> __migrate_folio() skips the host-side folio_mc_copy().
I always thought that one of the nice things about using guest_memfd as a
memory backend, as opposed to host userspace mappings, is that the host
cannot unmap VM memory because of KSM, automatic NUMA balancing, hugepage
collapse, compaction, etc, acting on the host userspace mapping of the
VM memory, and outside of the VMM's or KVM's control.
I think it would be useful to preserve this behaviour, even in the absence
of confidential VMs (i.e, guest_memfd file descriptor created with
GUEST_MEMFD_FLAG_MMAP).
Thanks,
Alex
>
> Testing
> -------
> Host: 7.1-rc7 + this, 2 NUMA nodes
>
> - KVM selftest: allocate folios on node 0, migrate them to node 1 and
> back and verify resulting NUMA node and the folio contents at each
> step.
>
> - Firecracker [1]: booted a microVM backed by guest_memfd. While the
> guest was running, forced host-side migration of its folios via
> migratepages(8) and explicit move_pages(2) of guest_memfd
> pages. Verify with /proc/firecracker_pid/numa_maps.
>
> [1] https://github.com/firecracker-microvm/firecracker/tree/feature/secret-hiding
> and change builder.rs to remove GUEST_MEMFD_FLAG_NO_DIRECT_MAP from
> vm.create_guest_memfd()
>
> Best regards,
> Shivank
>
> Signed-off-by: Shivank Garg <shivankg@amd.com>
> ---
> Shivank Garg (3):
> mm: split AS_UNMOVABLE back out of AS_INACCESSIBLE
> KVM: guest_memfd: support folio migration for non-confidential VMs
> KVM: selftests: exercise guest_memfd folio migration
>
> include/linux/pagemap.h | 24 ++++++--
> mm/compaction.c | 12 ++--
> mm/migrate.c | 2 +-
> tools/testing/selftests/kvm/guest_memfd_test.c | 77 ++++++++++++++++++++++++++
> virt/kvm/guest_memfd.c | 49 ++++++++++++++--
> 5 files changed, 149 insertions(+), 15 deletions(-)
> ---
> base-commit: 4549871118cf616eecdd2d939f78e3b9e1dddc48
> change-id: 20260611-shivank-gmem-migrate-8c1c519b30a6
>
> Best regards,
> --
> Shivank Garg <shivankg@amd.com>
>
>
^ permalink raw reply
* RE: [RFC PATCH 0/6] Support virtio-mem memory hotplug in TDX guests
From: Duan, Zhenzhong @ 2026-06-15 7:54 UTC (permalink / raw)
To: Kiryl Shutsemau
Cc: marcandre.lureau@redhat.com, david@kernel.org, Edgecombe, Rick P,
prsampat@amd.com, pbonzini@redhat.com, mst@redhat.com,
peterx@redhat.com, Qiang, Chenyi, Reshetova, Elena,
michaeluth@amd.com, ackerleytng@google.com,
linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev,
virtualization@lists.linux.dev, x86@kernel.org, Xu, Yilun,
Li, Xiaoyao, Peng, Chao P
In-Reply-To: <aiv0y-Op9bfP-CVO@thinkstation>
>-----Original Message-----
>From: Kiryl Shutsemau <kas@kernel.org>
>Subject: Re: [RFC PATCH 0/6] Support virtio-mem memory hotplug in TDX guests
>
>On Thu, Jun 04, 2026 at 05:35:45AM -0400, Zhenzhong Duan wrote:
>> 2. Re-accepting already-accepted memory returns errors. Ignoring these errors
>> can mislead the guest into believing re-accepted memory is zeroed when it
>> contains stale data.
>
>Re-accepting concern is valid, but often overblown.
> Reaccepting memory that never got allocated is fine.
I don't quite understand. "Reaccepting" implies accepting memory that was
already accepted earlier. For that to happen, the memory must have already
been allocated on the VMM side, correct?
>
>> == About this series ==
>>
>> This series takes a different direction, supporting start-private memory
>> and addressing the limitations of previous series [1] by implementing a
>> callback-based infrastructure that integrates TDX memory acceptance and
>> release operations with proper subblock granularity.
>
>You are presenting these callbacks as generic memory hotplug thingy, but
>it is only plugged into virtio mem. ACPI hotplug won't accept/release
>memory unless I miss something. Are you expecting them to cover non
>virtio cases too?
You are right, I didn't add ACPI hotplug in this series. I'm working on RFCv2
supporting both virtio-mem and ACPI hotplug in eager/lazy accept mode.
>
>And these callbacks feels like very ad-hoc solution.
OK, will drop the callbacks in RFCv2.
>
>> See Rick and Paolo's
>> discussion about using TDG.MEM.PAGE.RELEASE in [1].
>
>Having RELEASE in hotplug path without addressing private->shared
>conversion first is odd. That's the most obvious path that has to be
>covered first.
>
>Hm?
This patch series assumes that memory is plugged in as private memory
and must remain private prior to being unplugged. During the unplugging
process, memory is allocated from the buddy system and marked as
FAKE_OFFLINE. Because all free memory within the buddy system is
strictly private, shared memory can never be unplugged.
Shared memory is originally converted from private memory allocated by
the buddy system. Consequently, the driver must convert any shared
memory back to private and return it to the buddy system before it can
be unplugged.
>
>> == Future work ==
>> support lazy accept
>
>It would be nice to have some outline on how we will get there to
>understand if this patchset is stepping stone or dead end that has to be
>thrown away later on.
I realized the callbacks are specially used for eager accept, they are not
useful for lazy accept. So, I will drop them in RFCv2.
>
>Hot[un]plug is often used to manager overcommited host. Eager accept
>might be counter-productive.
Agree, I should have taken lazy accept into consideration from start.
Thanks
Zhenzhong
^ permalink raw reply
* Re: [RFC PATCH 13/15] KVM: TDX: Support event-notify interrupts only with userspace quoting
From: Adrian Hunter @ 2026-06-15 4:39 UTC (permalink / raw)
To: Peter Fang
Cc: Xu Yilun, kas, djbw, rick.p.edgecombe, x86, linux-coco,
linux-kernel, kvm, sohil.mehta, yilun.xu, baolu.lu,
zhenzhong.duan, xiaoyao.li
In-Reply-To: <20260614125750.GB3425618@pedri>
>>> @@ -7335,6 +7335,9 @@ inputs and outputs of the TDVMCALL. Currently the following values of
>>> queued successfully, the TDX guest can poll the status field in the
>>> shared-memory area to check whether the Quote generation is completed or
>>> not. When completed, the generated Quote is returned via the same buffer.
>>> + If the host kernel generates Quotes through the TDX Quoting service provided
>>> + by the TDX module, KVM processes the GetQuote request and it will not appear
>>> + in userspace.
>>
>> There is an Attestation section in Documentation/virt/kvm/x86/intel-tdx.rst
>> that could be updated too.
>
> Can you please point me to it? I couldn't find that section in that
> file.
Sorry, got he file name wrong: Documentation/arch/x86/tdx.rst
^ permalink raw reply
* Re: [RFC PATCH 13/15] KVM: TDX: Support event-notify interrupts only with userspace quoting
From: Peter Fang @ 2026-06-14 12:57 UTC (permalink / raw)
To: Adrian Hunter
Cc: Xu Yilun, kas, djbw, rick.p.edgecombe, x86, linux-coco,
linux-kernel, kvm, sohil.mehta, yilun.xu, baolu.lu,
zhenzhong.duan, xiaoyao.li
In-Reply-To: <7090f4af-3a6d-40fd-82ab-0ba6272534dd@intel.com>
On Thu, Jun 11, 2026 at 10:36:52PM +0300, Adrian Hunter wrote:
> On 22/05/2026 06:41, Xu Yilun wrote:
> > From: Peter Fang <peter.fang@intel.com>
> >
> > Tie userspace SetupEventNotifyInterrupt support to userspace Quote
> > generation. Delivering event-notify interrupts via userspace breaks if
> > KVM never exits to userspace in the first place.
>
> Breaks how exactly?
>
> Seems like a TDX guest has no way to know whether the VMM will use
> the Event Notify Interrupt anyway, so it cannot rely upon it, so
> it should already handle the case when the interrupt does not fire.
Hm that's an interesting point. But isn't the whole point of
SetupEventNotifyInterrupt to set up a contract with the host VMM? The
GHCI spec is quite loose about this.
If we say "the host VMM is not required to honor this contract", then
maybe this doesn't truly break anything. But then this stance kind of
makes this whole feature moot, or at least not very useful?
Not adding this patch feels like making this problem worse, right?
Because now we will have platforms that won't ever fire these
interrupts, and the host still tells the guest SetupEventNotifyInterrupt
is supported.
>
> >
> > No known guest currently requires event-notify interrupt support, so
> > defer adding in-kernel support for now. Linux TDX guests use polling
> > only.
>
> If no guest is using it, then why does it need special treatment?
Just to maintain status quo basically. Seems like previously there was
some interest in adding this support to the guest at some point. This
patch simply turns off this feature when quoting is not done in
userspace. But platforms that do quoting in userspace (e.g. don't
support DICE extension) can observe the same behavior as today, if/when
such a guest comes into existence.
>
> >
> > @@ -7335,6 +7335,9 @@ inputs and outputs of the TDVMCALL. Currently the following values of
> > queued successfully, the TDX guest can poll the status field in the
> > shared-memory area to check whether the Quote generation is completed or
> > not. When completed, the generated Quote is returned via the same buffer.
> > + If the host kernel generates Quotes through the TDX Quoting service provided
> > + by the TDX module, KVM processes the GetQuote request and it will not appear
> > + in userspace.
>
> There is an Attestation section in Documentation/virt/kvm/x86/intel-tdx.rst
> that could be updated too.
Can you please point me to it? I couldn't find that section in that
file.
>
> > + KVM only supports version 1 of the GetQuote request.
>
> Is that relevant here?
Documenting this came up during some internal discussions. But yeah it
looks a bit out of place. I can remove it.
>
> >
> > * ``TDVMCALL_GET_TD_VM_CALL_INFO``: the guest has requested the support
> > status of TDVMCALLs. The output values for the given leaf should be
> > @@ -7342,7 +7345,10 @@ inputs and outputs of the TDVMCALL. Currently the following values of
> > field of the union.
> >
> > * ``TDVMCALL_SETUP_EVENT_NOTIFY_INTERRUPT``: the guest has requested to
> > - set up a notification interrupt for vector ``vector``.
> > + set up a notification interrupt for vector ``vector``. Since this TDVMCALL
> > + is used to optimize ``TDVMCALL_GET_QUOTE``, KVM disables this support in
> > + userspace VMM if ``TDVMCALL_GET_QUOTE`` is completely handled in the kernel.
> > + KVM may add kernel support for this in the future.
>
> Is that really necessary?
I think this is related to the discussion above about how hard host VMM
should try to honor the SetupEventNotifyInterrupt contract.
>
^ permalink raw reply
* Re: [RFC PATCH 12/15] KVM: TDX: Add in-kernel Quote generation
From: Peter Fang @ 2026-06-14 11:57 UTC (permalink / raw)
To: Dan Williams (nvidia)
Cc: Xu Yilun, kas, rick.p.edgecombe, x86, linux-coco, linux-kernel,
kvm, sohil.mehta, yilun.xu, baolu.lu, zhenzhong.duan, xiaoyao.li
In-Reply-To: <6a2ca24f16277_9b85510070@djbw-dev.notmuch>
On Fri, Jun 12, 2026 at 05:20:31PM -0700, Dan Williams (nvidia) wrote:
> [..]
> > +static u64 __get_quote_kernel(struct kvm_vcpu *vcpu, struct tdx_quote_req *req,
> > + size_t req_len, gpa_t req_gpa, size_t total_len)
> > +{
> > + struct tdx_td *td = &to_kvm_tdx(vcpu->kvm)->td;
> > +
> > + /* Only support version 1 as defined in the GHCI spec */
> > + if (req->version != 1)
> > + return TDX_QUOTE_STATUS_ERROR;
> > +
> > + if ((size_t)req->in_len + TDX_QUOTE_REQ_HDR_SIZE > req_len)
> > + return TDX_QUOTE_STATUS_ERROR;
> > +
> > + /* The caller frees the quote data */
>
> No, it is freed by cleanup as far as I can see
Ah makes sense. I'll fix it up.
>
> > + void *quote_data __free(kvfree) =
>
> ...this shadows the global "quote_data". A global really should be
> properly namespaced.
Good point... I'll fix the naming. Thanks.
^ permalink raw reply
* Re: [RFC PATCH 10/15] x86/tdx: Move and rename Quote request structure
From: Peter Fang @ 2026-06-14 11:51 UTC (permalink / raw)
To: Dan Williams (nvidia)
Cc: Xu Yilun, kas, rick.p.edgecombe, x86, linux-coco, linux-kernel,
kvm, sohil.mehta, yilun.xu, baolu.lu, zhenzhong.duan, xiaoyao.li
In-Reply-To: <6a2c9e7570dd_9b855100eb@djbw-dev.notmuch>
On Fri, Jun 12, 2026 at 05:04:05PM -0700, Dan Williams (nvidia) wrote:
> > }
> > #endif /* CONFIG_INTEL_TDX_GUEST && CONFIG_KVM_GUEST */
> >
> > +#if defined(CONFIG_INTEL_TDX_GUEST) || defined(CONFIG_KVM_INTEL_TDX)
> > +/* struct tdx_quote_req: Format of Quote request message.
> > + * @version: Quote format version, filled by TD.
> > + * @status: Status code of Quote request, filled by VMM.
> > + * @in_len: Length of TDREPORT, filled by TD.
> > + * @out_len: Length of Quote data, filled by VMM.
> > + * @data: Quote data on output or TDREPORT on input.
> > + *
> > + * More details of Quote request message can be found in TDX
> > + * Guest-Host Communication Interface (GHCI) for Intel TDX 1.0,
> > + * section titled "TDG.VP.VMCALL<GetQuote>"
> > + */
> > +struct tdx_quote_req {
> > + u64 version;
> > + u64 status;
> > + u32 in_len;
> > + u32 out_len;
> > + u8 data[];
> > +};
> > +#endif /* CONFIG_INTEL_TDX_GUEST || CONFIG_KVM_INTEL_TDX */
>
> Drop the ifdef guards.
>
> There is no cost to allowing a data structure to be defined
> unconditionally. Usually the ifdef guards are to prevent compilation
> errors when symbols do not resolve.
>
> Otherwise looks ok.
>
> Reviewed-by: Dan Williams <djbw@kernel.org>
Will do, thanks for the review Dan!
^ permalink raw reply
* Re: [RFC PATCH 10/15] x86/tdx: Move and rename Quote request structure
From: Peter Fang @ 2026-06-14 11:50 UTC (permalink / raw)
To: Adrian Hunter
Cc: Xu Yilun, kas, djbw, rick.p.edgecombe, x86, linux-coco,
linux-kernel, kvm, sohil.mehta, yilun.xu, baolu.lu,
zhenzhong.duan, xiaoyao.li
In-Reply-To: <5f9474ed-bacb-44d5-a0fc-5a29a1e79b60@intel.com>
On Thu, Jun 11, 2026 at 08:16:37PM +0300, Adrian Hunter wrote:
> > -static int wait_for_quote_completion(struct tdx_quote_buf *quote_buf, u32 timeout)
> > +static int wait_for_quote_completion(struct tdx_quote_req *quote_buf, u32 timeout)
>
> Seems inconsistent to rename the struct but not the variable names
Good catch, I'll fix that.
>
> > {
> > int i = 0;
>
> Please note, the timeout condition in wait_for_quote_completion() is
> broken, in that the final value of i is timeout + 1 not timeout.
> Since you are in the same area, that needs fixing that too.
Thanks for catching that. This needs to be fixed. We can submit a
separate guest-only patch.
>
^ permalink raw reply
* Re: [RFC PATCH 09/15] x86/virt/tdx: Add interface to generate a Quote
From: Peter Fang @ 2026-06-14 11:36 UTC (permalink / raw)
To: Adrian Hunter
Cc: Xu Yilun, kas, djbw, rick.p.edgecombe, x86, linux-coco,
linux-kernel, kvm, sohil.mehta, yilun.xu, baolu.lu,
zhenzhong.duan, xiaoyao.li
In-Reply-To: <7c7d21c6-1f8a-42c6-a950-8fd61d702679@intel.com>
On Thu, Jun 11, 2026 at 08:15:50PM +0300, Adrian Hunter wrote:
> On 22/05/2026 06:41, Xu Yilun wrote:
> > From: Peter Fang <peter.fang@intel.com>
> >
> > Use the TDX Quoting extension's TDH.QUOTE.GET SEAMCALL to generate a
> > Quote. Since the interface is shared across all KVM instances,
> > serialize access to the SEAMCALL buffer with a mutex.
>
> Isn't the concurrency configurable, so supporting only 1 instance
> is a decision of the software implementation, not a TDX limitation?
Ah yes, I should document that. I'll put that in the patch log.
>
> > +static u64 tdx_quote_get(struct tdx_td *td, u64 in_data_pa, u64 in_data_len,
> > + u64 hpa_list_pa, u64 total_len, u64 *quote_len)
> > +{
> > + struct tdx_module_args args = {
> > + .rcx = tdx_tdr_pa(td),
> > + /* Don't bother specifying the quote id */
>
> Need to explain why
Will do. It's because we use whatever the default Quote ID is.
>
> ...
>
> > + r = tdx_quote_get(td, quote_data.hpa_list[0], (u64)in_data_len,
> > + quote_data.hpa_list_pa, quote_data.buf_len, &out_len);
> > + if (r || !out_len || out_len > quote_data.buf_len)
>
> Is r != TDX_SUCCESS more consistent
Yep I can fix that. Thanks.
>
^ permalink raw reply
* Re: [RFC PATCH 09/15] x86/virt/tdx: Add interface to generate a Quote
From: Peter Fang @ 2026-06-14 11:29 UTC (permalink / raw)
To: Edgecombe, Rick P
Cc: kas@kernel.org, djbw@kernel.org, yilun.xu@linux.intel.com,
x86@kernel.org, Xu, Yilun, Duan, Zhenzhong,
baolu.lu@linux.intel.com, Li, Xiaoyao,
linux-kernel@vger.kernel.org, Mehta, Sohil, kvm@vger.kernel.org,
linux-coco@lists.linux.dev
In-Reply-To: <a10ad58ed8092e4e7d81be1995438efd21647fde.camel@intel.com>
On Thu, May 28, 2026 at 03:30:45PM -0700, Edgecombe, Rick P wrote:
> > +
> > + /* TDH.QUOTE.GET expects the input data to fit in a page */
> > + if (in_data_len > PAGE_SIZE)
> > + return NULL;
>
> Do we really need this check? We can't trust the caller to pass the right size?
There is a similar check for this in_data_len on the KVM side in patch
12, but it is for a different reason. The check in KVM is to make sure
it maps valid guest memory pages into the kernel, while here we make
sure it complies with the SEAMCALL API. That said, the KVM check does
make the check here kinda redundant... I can remove this for simplicity.
>
> > +
> > + mutex_lock(&tdx_quote_lock);
> > +
> > + /*
> > + * Use the first page of the quote buffer for input data. The buffer
> > + * must be at least one page in size. @in_data may not be page-aligned,
> > + * but TDH.QUOTE.GET expects page-aligned addresses.
> > + */
> > + memcpy(quote_data.buf, in_data, (size_t)in_data_len);
> > +
> > + r = tdx_quote_get(td, quote_data.hpa_list[0], (u64)in_data_len,
> > + quote_data.hpa_list_pa, quote_data.buf_len, &out_len);
> > + if (r || !out_len || out_len > quote_data.buf_len)
>
>
> How do these various error conditions happen?
"r" is a SEAMCALL error just like any other SEAMCALL. If r == 0
(SUCCESS), there is no documented scenario for when "!out_len" or
"out_len > quote_data.buf_len" would occur. I would assume these would
be TDX module bugs.
The reason I check the last 2 conditions is mainly to protect the
kernel:
- "!out_len" will cause kvmemdup() to return ZERO_SIZE_PTR
- "out_len > quote_data.buf_len" will cause out-of-bounds memory
access in kvmemdup()
>
> > + goto out;
> > +
> > + /*
> > + * The quote buffer is a shared resource, so use it only for the
> > + * SEAMCALL and copy the data out as soon as possible.
> > + */
> > + quote_dup = kvmemdup(quote_data.buf, out_len, GFP_KERNEL);
>
> So at init time we allocate a vmalloc for the quote and pre-populate the
> hpa_list. Then we use it every time and copy the contents to a new vmalloc.
> Would it really be that hard to keep the hpa list allocation around, do a
> vmalloc here and update the pfn list. Then do get quote on that and pass back
> the vmalloc we just allocated? Just feels like global reuse way has extra pieces
> in it. Compared to the whole quoting operation, this vmalloc_to_pfn() loop is
> probably not very expensive.
Hm interesting idea. But a Quote buffer could be close to 4MB in the worst
case. Let's say max_quote_size is 3MB, that's 768 vmalloc_to_pfn() calls
each time... That sounds a bit excessive right?
The extra bits mainly come from using kvmemdup() I think. Having to use
kvfree() on it does feel a bit annoying but that was the tradeoff I
made...
>
^ permalink raw reply
* Re: [RFC PATCH 07/15] x86/virt/tdx: Prepare Quote buffer during extension bringup
From: Peter Fang @ 2026-06-14 10:28 UTC (permalink / raw)
To: Edgecombe, Rick P
Cc: kas@kernel.org, djbw@kernel.org, yilun.xu@linux.intel.com,
x86@kernel.org, Xu, Yilun, Duan, Zhenzhong,
baolu.lu@linux.intel.com, Li, Xiaoyao,
linux-kernel@vger.kernel.org, Mehta, Sohil, kvm@vger.kernel.org,
linux-coco@lists.linux.dev
In-Reply-To: <1a4d1126d6fe86e94fa8e1de6764656853e61106.camel@intel.com>
On Thu, May 28, 2026 at 03:30:36PM -0700, Edgecombe, Rick P wrote:
> On Fri, 2026-05-22 at 11:41 +0800, Xu Yilun wrote:
> > From: Peter Fang <peter.fang@intel.com>
> >
> > The host uses a Quote buffer to communicate with the TDX module when
> > generating Quotes.
> >
>
> Can this be put in common terms. This is going to mean nothing to someone
> reading this that doesn't already know the feature.
I'll add more background in common terms here.
>
> > Because the Quote buffer is shared with TDX guests,
>
> Why capitalize "Quote"?
This is again the balance between using common terms vs TDX language. In
general, TDX docs capitalize terms a lot. TDX attestation docs always
refer to the attestation blob as "Quotes".
I mainly went with "Quotes" in the logs because that term has already
been used everywhere in the tdx-guest code/logs (see tdx-guest.c). So I
wanted to preserve some consistency at least in the logs. In the added
host code and prints, I'm starting to just use "quotes" because that
seems to be the more common convention in the TDX host code. I'm happy
to make adjustments if this doesn't make sense.
>
> > prepare the required metadata during Quoting extension bringup.
>
> What does prepare the required metadata mean?
That's a poor choice of word on my part. I'll rephrase it in the next
revision. I mainly just wanted to convey "prepare struct quote_data".
>
> How does it being shared with TDX guest suggest this? Just that TDX guests will
> need them? Is the reason just that only one is needed, so do it during global
> init?
Yes, that's exactly it. I'll make it clearer.
>
> > +static struct quote_data {
> > + void *buf;
> > + u64 buf_len;
> > + u64 *hpa_list;
> > + phys_addr_t hpa_list_pa;
> > +} quote_data;
>
> Hmm, I think this should separate the type and variable declaration. It's not a
> common pattern. I don't think there is an official rule.
Sure, I'll fix this.
>
> > + qlist = vmalloc_array(qlist_npages, PAGE_SIZE);
> > + if (!qlist) {
> > + err = -ENOMEM;
> > + goto out_err;
>
> Just return ENOMEM here. vfree() doesn't do any work if passed NULL, but it's
> weird flow.
Will do.
>
> > + }
> > +
> > + /*
> > + * Make sure unfilled entries are always -1, which means NULL in TDX.
>
> Huh?
I'll add more explanation here (see below).
>
> > + * Only the last page needs to be filled. All the other pages will be
> > + * fully populated.
> > + */
> > + memset((u8 *)qlist + (qlist_npages - 1) * PAGE_SIZE, 0xff, PAGE_SIZE);
>
> What are the entries? And what is a -1 in u8? Or is it supposed to be u64?
> Please make this a lot clearer.
Yeah I was trying to create all-1 u64 entries. This is pretty
under-commented. I'll redo the comments.
>
> > + /* Populate HPA_LINKED_LIST as per TDX ABI spec */
> > + for (i = 0, j = 0; j < nr_pages; i++) {
> > + if ((i % HPAS_PER_PAGE) == HPAS_PER_PAGE - 1) {
> > + /*
> > + * The last entry always points to the next page. The
> > + * address of the following entry must be on next page's
> > + * boundary.
> > + */
>
> Can you maybe just explain this format that you are building in like one
> sentence at the beginning of the function? "The quote buffer is passed to the
> tdx module in a format that like... (some common terms that have no TDX
> jargon)."
Will do. This part is pretty under-commented as well.
>
> > + qdata->buf = qbuf;
> > + qdata->buf_len = (u64)nr_pages * PAGE_SIZE;
> > + qdata->hpa_list = qlist;
> > +
> > + pfn = vmalloc_to_pfn(qlist);
>
> Do we need a vmalloc_to_pa() helper? Maybe put it in terms of tdx format. Like
> vmalloc_pfn_to_tdxpa() and keep it here? The tdx update stuff does this a bunch
> too.
That's a really good idea. I'll do that.
>
> > + qdata->hpa_list_pa = PFN_PHYS(pfn);
> > +
> > + return 0;
> > +
> > +out_err:
> > + vfree(qlist);
> > +
> > + return err;
>
> It only returns -ENOMEM, so do we need the err var?
Good point. I think I had some other errors that I later removed. I'll
just return -ENOMEM directly here.
>
> > +}
> > +
> > static void tdx_quote_init(void)
> > {
> > struct tdx_module_args args = {};
> > + unsigned int nr_quote_pages;
> > u64 r;
> >
> > do {
> > @@ -1218,7 +1295,13 @@ static void tdx_quote_init(void)
> > return;
> >
> > /* Quoting metadata is valid only after initialization */
> > - get_tdx_sys_info_quote(&tdx_sysinfo.quote);
> > + if (get_tdx_sys_info_quote(&tdx_sysinfo.quote))
> > + return;
>
> How come this patch gets error handling? Why is it needed now when it wasn't
> before?
Previously, get_tdx_sys_info_quote() just happened to be the last
statement in tdx_quote_init() so getting an error didn't require an
early return. tdx_quote_init() wasn't doing much at the time. But now
the code can't see a valid max_quote_size if get_tdx_sys_info_quote()
fails.
>
> > +
> > + nr_quote_pages = PAGE_ALIGN(tdx_sysinfo.quote.max_quote_size) /
> > + PAGE_SIZE;
> > + if (tdx_quote_create_buf(nr_quote_pages, "e_data))
> > + pr_err("Failed to create quote buffer\n");
>
> Err... what happens in ENOMEM scenario? NULL pointer later?
Yes. struct quote_data remains uninitialized so it will have NULL
pointers. All the added APIs will take this into account so there won't
be NULL pointer accesses.
>
> > }
> >
> > /* Initialize the TDX Module Extensions then Extension-SEAMCALLs can be used */
>
^ permalink raw reply
* Re: [RFC PATCH 06/15] x86/virt/tdx: Initialize Quoting extension during bringup
From: Peter Fang @ 2026-06-14 7:50 UTC (permalink / raw)
To: Dan Williams (nvidia)
Cc: Xu Yilun, kas, rick.p.edgecombe, x86, linux-coco, linux-kernel,
kvm, sohil.mehta, yilun.xu, baolu.lu, zhenzhong.duan, xiaoyao.li
In-Reply-To: <6a2c9d8b8bfe9_9b85510018@djbw-dev.notmuch>
On Fri, Jun 12, 2026 at 05:00:11PM -0700, Dan Williams (nvidia) wrote:
> Xu Yilun wrote:
> > From: Peter Fang <peter.fang@intel.com>
> >
> > Initialize the Quoting extension and fetch its metadata during TDX
> > bringup.
> >
> > Because Quoting is an optional TDX feature, do not let its
> > initialization failures cause TDX bringup to fail.
>
> Is this micro-optimization worth it? What are the classes of quote-init
> failures vs just make the policy be anything in the module must init.
Since there is a fallback option to do the Quoting in userspace, I think
it is probably not worth shooting down TDX entirely over quote-init
failures.
The quote-init failures can come from:
1. Quoting init SEAMCALL failures, which look pretty opaque to the
kernel and there's not much it can do about it.
2. Quoting buffer allocation failures, which *are* understood by the
kernel, and it could maybe try something else. Right now, we just
treat it the same as 1.
This is helpful because I think the question of "what if the Quoting
extension fails" has come up enough times that it warrants some
explanation in the patch log. Thanks.
>
> > This patch does not include the opt-in portion of the initialization.
> > It mainly lays the groundwork for TDX Quoting support. Opt-in will be
> > added in a follow-up patch once the feature can be properly used by the
> > system.
>
> It is unconditionally calling quote init even if the feature is not
> present. Is that not a problem?
Good question... I should reorder the patches so this looks more
straightforward. I enable everything in patch 15 (including the check
for the Quoting feature) and I think that just creates confusion for
folks looking at this patch.
>
^ permalink raw reply
* Re: [RFC PATCH 06/15] x86/virt/tdx: Initialize Quoting extension during bringup
From: Peter Fang @ 2026-06-14 7:20 UTC (permalink / raw)
To: Adrian Hunter
Cc: Xu Yilun, kas, djbw, rick.p.edgecombe, x86, linux-coco,
linux-kernel, kvm, sohil.mehta, yilun.xu, baolu.lu,
zhenzhong.duan, xiaoyao.li
In-Reply-To: <55b1972a-bfc9-4229-a7c6-7d46b03d9e6c@intel.com>
On Thu, Jun 11, 2026 at 07:22:18PM +0300, Adrian Hunter wrote:
> On 22/05/2026 06:41, Xu Yilun wrote:
> > From: Peter Fang <peter.fang@intel.com>
> >
> > Initialize the Quoting extension and fetch its metadata during TDX
> > bringup.
> >
> > Because Quoting is an optional TDX feature, do not let its
> > initialization failures cause TDX bringup to fail.
>
> Is there a reason Linux needs to support TDX with failed Quote
> extension initialization?
The Quoting extension is not the only way to get TD Quotes. If this
extension fails, the host can still fall back to the legacy SGX-based
Quoting in userspace. I think the decision to actually fall back can be
left to userspace at that point.
>
> > +static void tdx_quote_init(void)
> > +{
> > + struct tdx_module_args args = {};
> > + u64 r;
> > +
> > + do {
> > + r = seamcall(TDH_QUOTE_INIT, &args);
> > + } while (r == TDX_INTERRUPTED_RESUMABLE);
> > +
> > + if (r)
>
> Elsewhere it tends to be:
>
> if (r != TDX_SUCCESS)
Good catch. I'll fix this. Thanks!
>
^ permalink raw reply
* Re: [RFC PATCH 06/15] x86/virt/tdx: Initialize Quoting extension during bringup
From: Peter Fang @ 2026-06-14 7:10 UTC (permalink / raw)
To: Edgecombe, Rick P
Cc: kas@kernel.org, djbw@kernel.org, yilun.xu@linux.intel.com,
x86@kernel.org, Xu, Yilun, Duan, Zhenzhong,
baolu.lu@linux.intel.com, Li, Xiaoyao,
linux-kernel@vger.kernel.org, Mehta, Sohil, kvm@vger.kernel.org,
linux-coco@lists.linux.dev
In-Reply-To: <f9ebc92839c94430055fe2a48114054a39b0e56e.camel@intel.com>
On Thu, May 28, 2026 at 02:35:49PM -0700, Edgecombe, Rick P wrote:
> On Fri, 2026-05-22 at 11:41 +0800, Xu Yilun wrote:
> > From: Peter Fang <peter.fang@intel.com>
> >
> > Initialize the Quoting extension and fetch its metadata during TDX
> > bringup.
> >
> > Because Quoting is an optional TDX feature, do not let its
> > initialization failures cause TDX bringup to fail.
> >
> > This patch
> >
>
> Don't say "this patch" in tip logs. The patch is a temporary format, and some
> x86 maintainers hate the term in logs.
Thanks, will fix in the next revision.
>
> > does not include the opt-in portion of the initialization.
> > It mainly lays the groundwork for TDX Quoting support. Opt-in will be
> > added in a follow-up patch once the feature can be properly used by the
> > system.
>
> This could be imperative mood.
Will fix this as well.
>
> >
> > Signed-off-by: Peter Fang <peter.fang@intel.com>
> > Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
>
^ permalink raw reply
* Re: [RFC PATCH 05/15] x86/virt/tdx: Move tdx_tdr_pa() up in the file
From: Peter Fang @ 2026-06-14 7:04 UTC (permalink / raw)
To: Adrian Hunter
Cc: Xu Yilun, kas, djbw, rick.p.edgecombe, x86, linux-coco,
linux-kernel, kvm, sohil.mehta, yilun.xu, baolu.lu,
zhenzhong.duan, xiaoyao.li
In-Reply-To: <0f4ee112-59c6-49b0-8d0b-886f32ec410a@intel.com>
On Thu, Jun 11, 2026 at 07:21:17PM +0300, Adrian Hunter wrote:
> On 22/05/2026 06:41, Xu Yilun wrote:
> > From: Peter Fang <peter.fang@intel.com>
> >
> > Move the tdx_tdr_pa() in preparation for upcoming changes to use them
>
> them -> it
Ack. Thanks for catching this.
>
^ permalink raw reply
* Re: [PATCH 04/15] x86/virt/tdx: Enable the Extensions right after basic TDX Module init
From: Peter Fang @ 2026-06-14 7:00 UTC (permalink / raw)
To: Xu Yilun
Cc: Kishen Maloor, kas, djbw, rick.p.edgecombe, x86, linux-coco,
linux-kernel, kvm, sohil.mehta, yilun.xu, baolu.lu,
zhenzhong.duan, xiaoyao.li
In-Reply-To: <aiaVk9Lx7iakgd4g@yilunxu-OptiPlex-7050>
On Mon, Jun 08, 2026 at 06:12:35PM +0800, Xu Yilun wrote:
>
> >
> > The handling of tdx_quote_init() in Patch 6 suggests a more
> > best-effort approach.
>
> TDX Quoting is however a clear self-contained add-on feature from OS POV.
> Though I'm not sure if a TDX platform is still a safe TCB with DICE
> available but failed, and good for "best-effort" policy? Maybe Peter
> could answer.
The DICE extension is just one of the ways to generate a Quote for the
guest. If DICE is not available, TDX can fall back to the existing
userspace SGX Quoting flow. So I think a best-effort approach makes
sense here.
> >
^ permalink raw reply
* Re: [RFC PATCH 14/15] x86/virt/tdx: Embed version info in SEAMCALL leaf function definitions
From: Xu Yilun @ 2026-06-13 15:55 UTC (permalink / raw)
To: Adrian Hunter
Cc: kas, djbw, rick.p.edgecombe, x86, peter.fang, linux-coco,
linux-kernel, kvm, sohil.mehta, yilun.xu, baolu.lu,
zhenzhong.duan, xiaoyao.li
In-Reply-To: <dd9027c7-ea84-4cee-9484-4e464a766b0d@intel.com>
On Fri, Jun 12, 2026 at 08:47:26AM +0300, Adrian Hunter wrote:
> On 22/05/2026 06:41, Xu Yilun wrote:
> > Embed version information in SEAMCALL leaf function definitions rather
> > than let the caller open code them. For now, only TDH.VP.INIT is
> > involved.
>
> > @@ -31,7 +44,7 @@
> > #define TDH_VP_CREATE 10
> > #define TDH_MNG_KEY_FREEID 20
> > #define TDH_MNG_INIT 21
> > -#define TDH_VP_INIT 22
> > +#define TDH_VP_INIT SEAMCALL_LEAF_VER(22, 1)
>
> FWIW I find the macro a bit ugly, and hiding the version number in
> the leaf number macro a little counter-intuitive compared with setting
> it at the call site. It anyway needs some explanation at the call site.
We actually discussed about this and realized we don't need to keep
version. This is because:
1. Newer version SEAMCALLs are always compatible with older ones.
2. System security requires us to stop using an older TDX module when
there is a newer one. So don't try to support an older TDX module
which doesn't understand newer version SEAMCALLs.
https://lore.kernel.org/all/ca331aa3-6304-4e07-9ed9-94dc69726382@intel.com/
>
> > @@ -2217,8 +2217,8 @@ u64 tdh_vp_init(struct tdx_vp *vp, u64 initial_rcx, u32 x2apicid)
> > .r8 = x2apicid,
> > };
> >
> > - /* apicid requires version == 1. */
> > - return seamcall(TDH_VP_INIT | (1ULL << TDX_VERSION_SHIFT), &args);
> > + /* apicid requires version == 1. See TDH_VP_INIT definition.*/
> > + return seamcall(TDH_VP_INIT, &args);
>
> Now the reader has to go look at TDH_VP_INIT.
mm.. I think I should just delete the comment.
^ permalink raw reply
* Re: [RFC PATCH 12/15] KVM: TDX: Add in-kernel Quote generation
From: Dan Williams (nvidia) @ 2026-06-13 0:20 UTC (permalink / raw)
To: Xu Yilun, kas, djbw, rick.p.edgecombe, x86, peter.fang
Cc: linux-coco, linux-kernel, kvm, sohil.mehta, yilun.xu, yilun.xu,
baolu.lu, zhenzhong.duan, xiaoyao.li
In-Reply-To: <20260522034128.3144354-13-yilun.xu@linux.intel.com>
Xu Yilun wrote:
> From: Peter Fang <peter.fang@intel.com>
>
> Provide an in-kernel path for TDX Quote generation when handling
> TDG.VP.VMCALL<GetQuote>, without requiring an exit to userspace.
>
> Use the core TDX API when the TDX Quoting extension is available. For
> simplicity, each KVM guest checks for availability only once during
> initialization. KVM does not handle Quoting service disruptions.
>
> Signed-off-by: Peter Fang <peter.fang@intel.com>
> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
> ---
[..]
> +static u64 __get_quote_kernel(struct kvm_vcpu *vcpu, struct tdx_quote_req *req,
> + size_t req_len, gpa_t req_gpa, size_t total_len)
> +{
> + struct tdx_td *td = &to_kvm_tdx(vcpu->kvm)->td;
> +
> + /* Only support version 1 as defined in the GHCI spec */
> + if (req->version != 1)
> + return TDX_QUOTE_STATUS_ERROR;
> +
> + if ((size_t)req->in_len + TDX_QUOTE_REQ_HDR_SIZE > req_len)
> + return TDX_QUOTE_STATUS_ERROR;
> +
> + /* The caller frees the quote data */
No, it is freed by cleanup as far as I can see
> + void *quote_data __free(kvfree) =
...this shadows the global "quote_data". A global really should be
properly namespaced.
^ permalink raw reply
* Re: [PATCH 04/15] x86/virt/tdx: Enable the Extensions right after basic TDX Module init
From: Dan Williams (nvidia) @ 2026-06-13 0:08 UTC (permalink / raw)
To: Xu Yilun, kas, djbw, rick.p.edgecombe, x86, peter.fang
Cc: linux-coco, linux-kernel, kvm, sohil.mehta, yilun.xu, yilun.xu,
baolu.lu, zhenzhong.duan, xiaoyao.li
In-Reply-To: <20260522034128.3144354-5-yilun.xu@linux.intel.com>
Xu Yilun wrote:
> The detailed initialization flow for TDX Module Extensions has been
> fully implemented. Enable the flow after basic TDX Module
> initialization.
>
> Theoretically, the Extensions doesn't need to be enabled right after
> basic TDX initialization. It could be enabled right before the first
> Extension SEAMCALL is issued. That would save or postpone memory usage.
> But it isn't worth the complexity, the needs for the Extensions are vast
> but the savings are little for a typical TDX capable system (about
> 0.001% of memory). So the Linux decision is to just enable it along with
> the basic TDX.
No real point in rehashing the rationale for the "any available, all the
time" policy yet again especially when this directly conflicts with the
"relatively large amount" comment in the original cover letter.
Otherwise I agree with the proposed reordering of this initial series.
In general though, no big showstoppers for me in this first 4.
^ permalink raw reply
* Re: [RFC PATCH 10/15] x86/tdx: Move and rename Quote request structure
From: Dan Williams (nvidia) @ 2026-06-13 0:04 UTC (permalink / raw)
To: Xu Yilun, kas, djbw, rick.p.edgecombe, x86, peter.fang
Cc: linux-coco, linux-kernel, kvm, sohil.mehta, yilun.xu, yilun.xu,
baolu.lu, zhenzhong.duan, xiaoyao.li
In-Reply-To: <20260522034128.3144354-11-yilun.xu@linux.intel.com>
Xu Yilun wrote:
> From: Peter Fang <peter.fang@intel.com>
>
> struct tdx_quote_buf is currently used only by the guest, but the Quote
> buffer format will also be needed by the host for in-kernel Quote
> generation. Move the definition to tdx.h so it can be shared by both.
>
> Rename the struct to tdx_quote_req to better reflect its purpose.
>
> Signed-off-by: Peter Fang <peter.fang@intel.com>
> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
> ---
> arch/x86/include/asm/tdx.h | 21 +++++++++++++++++++++
> drivers/virt/coco/tdx-guest/tdx-guest.c | 25 +++----------------------
> 2 files changed, 24 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index bc512a00a0d0..945e6817abb2 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -96,6 +96,27 @@ static inline long tdx_kvm_hypercall(unsigned int nr, unsigned long p1,
> }
> #endif /* CONFIG_INTEL_TDX_GUEST && CONFIG_KVM_GUEST */
>
> +#if defined(CONFIG_INTEL_TDX_GUEST) || defined(CONFIG_KVM_INTEL_TDX)
> +/* struct tdx_quote_req: Format of Quote request message.
> + * @version: Quote format version, filled by TD.
> + * @status: Status code of Quote request, filled by VMM.
> + * @in_len: Length of TDREPORT, filled by TD.
> + * @out_len: Length of Quote data, filled by VMM.
> + * @data: Quote data on output or TDREPORT on input.
> + *
> + * More details of Quote request message can be found in TDX
> + * Guest-Host Communication Interface (GHCI) for Intel TDX 1.0,
> + * section titled "TDG.VP.VMCALL<GetQuote>"
> + */
> +struct tdx_quote_req {
> + u64 version;
> + u64 status;
> + u32 in_len;
> + u32 out_len;
> + u8 data[];
> +};
> +#endif /* CONFIG_INTEL_TDX_GUEST || CONFIG_KVM_INTEL_TDX */
Drop the ifdef guards.
There is no cost to allowing a data structure to be defined
unconditionally. Usually the ifdef guards are to prevent compilation
errors when symbols do not resolve.
Otherwise looks ok.
Reviewed-by: Dan Williams <djbw@kernel.org>
^ permalink raw reply
* Re: [RFC PATCH 06/15] x86/virt/tdx: Initialize Quoting extension during bringup
From: Dan Williams (nvidia) @ 2026-06-13 0:00 UTC (permalink / raw)
To: Xu Yilun, kas, djbw, rick.p.edgecombe, x86, peter.fang
Cc: linux-coco, linux-kernel, kvm, sohil.mehta, yilun.xu, yilun.xu,
baolu.lu, zhenzhong.duan, xiaoyao.li
In-Reply-To: <20260522034128.3144354-7-yilun.xu@linux.intel.com>
Xu Yilun wrote:
> From: Peter Fang <peter.fang@intel.com>
>
> Initialize the Quoting extension and fetch its metadata during TDX
> bringup.
>
> Because Quoting is an optional TDX feature, do not let its
> initialization failures cause TDX bringup to fail.
Is this micro-optimization worth it? What are the classes of quote-init
failures vs just make the policy be anything in the module must init.
> This patch does not include the opt-in portion of the initialization.
> It mainly lays the groundwork for TDX Quoting support. Opt-in will be
> added in a follow-up patch once the feature can be properly used by the
> system.
It is unconditionally calling quote init even if the feature is not
present. Is that not a problem?
^ permalink raw reply
* Re: [PATCH 02/15] x86/virt/tdx: Add extra memory to TDX Module for Extensions
From: Dan Williams (nvidia) @ 2026-06-12 23:49 UTC (permalink / raw)
To: Xu Yilun, kas, djbw, rick.p.edgecombe, x86, peter.fang
Cc: linux-coco, linux-kernel, kvm, sohil.mehta, yilun.xu, yilun.xu,
baolu.lu, zhenzhong.duan, xiaoyao.li
In-Reply-To: <20260522034128.3144354-3-yilun.xu@linux.intel.com>
Xu Yilun wrote:
> TDX Module introduces a new concept called "TDX Module Extensions" to
> support long running / hard-irq preemptible flows inside. This makes TDX
> Module capable of handling complex tasks through "Extension SEAMCALLs".
> Adding more memory to TDX Module is the first step to enable Extensions.
Like I said on the cover, I think "long running hard-irq preemptible"
invites more questions that it answers. The service calls are not "long
running" on their own. I think it is sufficient to say they are
resumable unlike typical calls that run to completion while monopolizing
the CPU.
> Currently, TDX Module memory use is relatively static. But, the
> Extensions need to use memory more dynamically. While 'static' here
> means the kernel provides necessary amount of memory to TDX Module for
> its basic functionalities, 'dynamic' means extra memory is needed only
> if new add-on features are to be enabled. So add a new memory feeding
> process backed by a new SEAMCALL TDH.EXT.MEM.ADD.
Rick commented on this as well, but a simpler way to say it is
extensions receive a one time memory pool allocation at init time. The
extension uses that pool as its baseline for its own internal state and
data for the service APIs it offers.
> The process is mostly the same as adding PAMT. The kernel queries TDX
> Module how much memory needed, allocates it, hands it over, and never
> gets it back.
>
> TDH.EXT.MEM.ADD uses a new parameter type HPA_LIST_INFO to provide
> control (private) pages to TDX Module. This type represents a list of
> pages for TDX Module to access. It needs a 'root page' which contains
> the list of HPAs of the pages. It collapses the HPA of the root page
> and the number of valid HPAs into a 64 bit raw value for SEAMCALL
> parameters. The root page is always a medium, TDX Module never keeps
> the root page.
I mention below, but I do not think the reader cares that the TDX Module
calls an array of physical addresses a "root" page.
>
> Introduce a tdx_clflush_hpa_list() helper to flush shared cache before
> SEAMCALL, to avoid shared cache writeback damaging these private pages.
>
> For now, TDX Module Extensions consumes relatively large amount of
> memory (~50MB). Use contiguous page allocation to avoid permanently
> fragment too much memory. Print the allocation amount on TDX Module
> Extensions initialization for visibility.
To be clear I believe there is a low chance of fragmentation given this
allocation happening early. However, at 10s of MB the benefit of
isolating blocks of PFNs that will never be returned, it makes to not
use the buddy allocator for that.
> Co-developed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
> ---
> arch/x86/virt/vmx/tdx/tdx.h | 1 +
> arch/x86/virt/vmx/tdx/tdx.c | 118 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 119 insertions(+)
>
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index a5eec8e3cc71..2335f88bbb10 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -46,6 +46,7 @@
> #define TDH_PHYMEM_PAGE_WBINVD 41
> #define TDH_VP_WR 43
> #define TDH_SYS_CONFIG 45
> +#define TDH_EXT_MEM_ADD 61
> #define TDH_SYS_DISABLE 69
>
> /*
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index c0c6281b08a5..622399d8da68 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -31,6 +31,7 @@
> #include <linux/syscore_ops.h>
> #include <linux/idr.h>
> #include <linux/kvm_types.h>
> +#include <linux/bitfield.h>
> #include <asm/page.h>
> #include <asm/special_insns.h>
> #include <asm/msr-index.h>
> @@ -1179,6 +1180,123 @@ static __init int init_tdmrs(struct tdmr_info_list *tdmr_list)
> return 0;
> }
>
> +static void tdx_clflush_hpa_list(struct page *root, unsigned int nr_pages)
> +{
> + u64 *entries = page_to_virt(root);
> + int i;
> +
> + for (i = 0; i < nr_pages; i++)
> + clflush_cache_range(__va(entries[i]), PAGE_SIZE);
> +}
> +
> +#define HPA_LIST_INFO_FIRST_ENTRY GENMASK_U64(11, 3)
> +#define HPA_LIST_INFO_PFN GENMASK_U64(51, 12)
> +#define HPA_LIST_INFO_LAST_ENTRY GENMASK_U64(63, 55)
> +
> +static u64 to_hpa_list_info(struct page *root, unsigned int nr_pages)
> +{
> + return FIELD_PREP(HPA_LIST_INFO_FIRST_ENTRY, 0) |
> + FIELD_PREP(HPA_LIST_INFO_PFN, page_to_pfn(root)) |
> + FIELD_PREP(HPA_LIST_INFO_LAST_ENTRY, nr_pages - 1);
> +}
> +
> +static int tdx_ext_mem_add(struct page *root, unsigned int nr_pages)
> +{
> + struct tdx_module_args args = {
> + .rcx = to_hpa_list_info(root, nr_pages),
> + };
> + u64 r;
> +
> + tdx_clflush_hpa_list(root, nr_pages);
> +
> + do {
> + /*
> + * TDH_EXT_MEM_ADD is designed to use output parameter RCX to
> + * override/update input parameter RCX, so the caller doesn't
> + * have to do manual parameter update on retry call.
> + */
> + r = seamcall_ret(TDH_EXT_MEM_ADD, &args);
> + } while (r == TDX_INTERRUPTED_RESUMABLE);
> +
> + if (r != TDX_SUCCESS)
> + return -EFAULT;
> +
> + return 0;
> +}
> +
> +static int tdx_ext_mem_setup(void)
> +{
> + unsigned int nr_pages;
> + struct page *page;
> + u64 *root;
> + unsigned int i;
> + int ret;
> +
> + nr_pages = tdx_sysinfo.ext.memory_pool_required_pages;
> + /*
> + * memory_pool_required_pages == 0 means no need to add pages,
> + * skip the memory setup.
> + */
> + if (!nr_pages)
> + return 0;
> +
> + root = kzalloc(PAGE_SIZE, GFP_KERNEL);
> + if (!root)
> + return -ENOMEM;
I think this "root" term is a holdover from the complicated TDX Connect
case where it might sometimes be this odd "singleton" object? You could
just make it this for actual type safety.
struct tdx_hpa_list {
u64 phys[PAGE_SIZE/sizeof(u64)];
}
> +
> + page = alloc_contig_pages(nr_pages, GFP_KERNEL, numa_mem_id(),
> + &node_online_map);
> + if (!page) {
> + ret = -ENOMEM;
> + goto out_free_root;
> + }
> +
> + for (i = 0; i < nr_pages;) {
> + unsigned int nents = min(nr_pages - i,
> + PAGE_SIZE / sizeof(*root));
This looks wrong, sizeof(struct page)?, or size of physical address?
Becomes less error prone if you do:
min(nr_pages - i, ARRAY_SIZE(hpa_list->phys))
> + int j;
> +
> + for (j = 0; j < nents; j++)
You can declare j in the for loop.
> + root[j] = page_to_phys(page + i + j);
> +
> + ret = tdx_ext_mem_add(virt_to_page(root), nents);
> + /*
> + * No SEAMCALLs to reclaim the added pages. For simple error
> + * handling, leak all pages.
> + */
> + WARN_ON_ONCE(ret);
Perhaps to be friendlier to folks without the source code in front of
them drop the comment and do:
WARN(ret, "Fatal: TDX Module failed (%d) to accept memory, stranded %ld pages\n", ret, nr_pages)
...the once flavor not needed, right? It's toast at this point.
^ permalink raw reply
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