* Re: [PATCH 2/2] x86/tdx: Accept hotplugged memory before online
From: Edgecombe, Rick P @ 2026-03-25 17:21 UTC (permalink / raw)
To: marcandre.lureau@redhat.com
Cc: pbonzini@redhat.com, bp@alien8.de, kas@kernel.org, Qiang, Chenyi,
hpa@zytor.com, mingo@redhat.com, linux-kernel@vger.kernel.org,
dave.hansen@linux.intel.com, tglx@kernel.org, kvm@vger.kernel.org,
linux-coco@lists.linux.dev, x86@kernel.org
In-Reply-To: <CAMxuvaytU-pM+rviUbNGWMhvbAYutwvaSXW_O=sn+QfOzF35Xw@mail.gmail.com>
On Wed, 2026-03-25 at 14:29 +0400, Marc-André Lureau wrote:
> > Does this depend on patch 1 somehow?
>
> Yes, if I plug, unplug and plug again I get this without PATCH 1:
> [root@rhel10-server ~]# [ 5707.392231] virtio_mem virtio5: plugged
> size: 0x80000000
> [ 5707.395583] virtio_mem virtio5: requested size: 0x0
>
> [root@rhel10-server ~]# [ 5714.648501] virtio_mem virtio5: plugged
> size: 0x2e00000
> [ 5714.651808] virtio_mem virtio5: requested size: 0x80000000
> [ 5714.676296] tdx: Failed to accept memory [0x108000000,
> 0x110000000)
> [ 5714.683980] tdx: Failed to accept memory [0x110000000,
> 0x118000000)
> [ 5714.686997] tdx: Failed to accept memory [0x140000000,
> 0x148000000)
> [ 5714.689989] tdx: Failed to accept memory [0x128000000,
> 0x130000000)
> [ 5714.694981] tdx: Failed to accept memory [0x148000000,
> 0x150000000)
> [ 5714.704064] tdx: Failed to accept memory [0x138000000,
> 0x140000000)
> [ 5714.710144] tdx: Failed to accept memory [0x118000000,
> 0x120000000)
> [ 5714.722532] tdx: Failed to accept memory [0x130000000,
> 0x138000000)
>
> My understanding is that QEMU should eventually unplug the memory and
> PUNCH_HOLE then KVM should TDH.MEM.PAGE.REMOVE, but that doesn't seem
> to happen. Is this strictly required? According to the specification,
> it may not be.
Ah, I see now! So the problem is not that the kernel is accidentally
re-accepting the memory. It's that host userspace is not actually
removing the memory during unplug. Hmm. Why not fix userspace then? If
the memory is unplugged it should not be usable anymore by the guest.
If it is still accessible then it seems kind of like a bug, no?
And! This totally justifies the warning. If the error is ignored, the
guest would think the memory is zeroed, but it could have old data in
it. It's exactly the kind of tricks a VMM could play to attack the
guest.
Another option could be to perform a TDG.MEM.PAGE.RELEASE TDCALL from
the guest when it unplugs the memory, to put it in an unaccepted state.
This would be more robust to buggy VMM behavior. But working around
buggy VM behavior would need a high bar.
^ permalink raw reply
* Re: [PATCH 0/7] KVM: x86: APX reg prep work
From: Chang S. Bae @ 2026-03-25 18:28 UTC (permalink / raw)
To: Sean Christopherson
Cc: Paolo Bonzini, Kiryl Shutsemau, kvm, x86, linux-coco,
linux-kernel
In-Reply-To: <abL8SW5JS1aV5goa@google.com>
On 3/12/2026 10:47 AM, Sean Christopherson wrote:
> On Thu, Mar 12, 2026, Chang S. Bae wrote:
>>
>> However, that is sort of what-if scenarios at best. The host kernel still
>> manages EGPR context switching through XSAVE. Saving EGPRs into regs[] would
>> introduce an oddity to synchronize between two buffers: regs[] and
>> gfpu->fpstate, which looks like unnecessary complexity.
No, this looks ugly. If guest EGPR state is saved in vcpu->arch.regs[],
the APX area there isn't necessary:
When the KVM API exposes state in XSAVE format, the frontend can handle
this separately. Alongside uABI <-> guest fpstate copy functions, new
copy functions may deal with the state between uABI <-> VCPU cache.
Further, one could think of exclusion as such:
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 76153dfb58c9..5404f9399eea 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -794,9 +794,10 @@ static u64 __init guest_default_mask(void)
{
/*
* Exclude dynamic features, which require userspace opt-in even
- * for KVM guests.
+ * for KVM guests, and APX as extended general-purpose register
+ * states are saved in the KVM cache separately.
*/
- return ~(u64)XFEATURE_MASK_USER_DYNAMIC;
+ return ~((u64)XFEATURE_MASK_USER_DYNAMIC | XFEATURE_MASK_APX);
}
But this default bitmask feeds into the permission bits:
fpu->guest_perm.__state_perm = guest_default_cfg.features;
fpu->guest_perm.__state_size = guest_default_cfg.size;
This policy looks clear and sensible: permission is granted only if
space is reserved to save the state. If there is a strong desire to save
memory, I think it should go through a more thorough review to revisit
this policy.
> Have you measured performance/latency overhead if KVM goes straight to context
> switching R16-R31 at entry/exit? With PUSH2/POP2, it's "only" 8 more instructions
> on each side.
Yup, when I check a prototype in the lab, it appears to be in the noise,
with less than 1% overall variance.
> If the overhead is in the noise, I'd be very strongly inclined to say KVM should
> swap at entry/exit regardless of kernel behavior so that we don't have to special
> case accesses on the back end.
Note: The hardware request discussed looks to be on-going. I don't know
the decision yet. But at least for now let me add you to the off-list
thread for your info.
Right now, I think the entry path may live with guest XCR0 in this
regard. Since XSETBV is trapped/emulated, the shadow XCR0 remains in
sync. The entry function can take an additional flag reflecting guest
XCR0.APX, and gate EGPR access accordingly.
Then, it looks to keep the behavior aligned with the architecture:
* On initial enable, EGPRs are zeroed on entry following XSETBV exit
* If APX is disabled and later re-enabled, regs[] retains the state
while XCR0.APX=0 and restores it when returning from the re-enabling
XSETBV exit.
^ permalink raw reply related
* [PATCH v5 0/2] dma-buf: heaps: system: add an option to allocate explicitly shared/decrypted memory
From: Jiri Pirko @ 2026-03-25 19:23 UTC (permalink / raw)
To: dri-devel, linaro-mm-sig, iommu, linux-media
Cc: sumit.semwal, benjamin.gaignard, Brian.Starkey, jstultz,
tjmercier, christian.koenig, m.szyprowski, robin.murphy, jgg,
leon, sean.anderson, ptesarik, catalin.marinas, aneesh.kumar,
suzuki.poulose, steven.price, thomas.lendacky, john.allen,
ashish.kalra, suravee.suthikulpanit, linux-coco
From: Jiri Pirko <jiri@nvidia.com>
Confidential computing (CoCo) VMs/guests, such as AMD SEV and Intel TDX,
run with private/encrypted memory which creates a challenge
for devices that do not support DMA to it (no TDISP support).
For kernel-only DMA operations, swiotlb bounce buffering provides a
transparent solution by copying data through shared memory.
However, the only way to get this memory into userspace is via the DMA
API's dma_alloc_pages()/dma_mmap_pages() type interfaces which limits
the use of the memory to a single DMA device, and is incompatible with
pin_user_pages().
These limitations are particularly problematic for the RDMA subsystem
which makes heavy use of pin_user_pages() and expects flexible memory
usage between many different DMA devices.
This patch series enables userspace to explicitly request shared
(decrypted) memory allocations from new dma-buf system_cc_shared heap.
Userspace can mmap this memory and pass the dma-buf fd to other
existing importers such as RDMA or DRM devices to access the
memory. The DMA API is improved to allow the dma heap exporter to DMA
map the shared memory to each importing device.
Based on dma-mapping-for-next e7442a68cd1ee797b585f045d348781e9c0dde0d
Jiri Pirko (2):
dma-mapping: introduce DMA_ATTR_CC_SHARED for shared memory
dma-buf: heaps: system: add system_cc_shared heap for explicitly
shared memory
drivers/dma-buf/heaps/system_heap.c | 103 ++++++++++++++++++++++++++--
include/linux/dma-mapping.h | 10 +++
include/trace/events/dma.h | 3 +-
kernel/dma/direct.h | 14 +++-
kernel/dma/mapping.c | 13 +++-
5 files changed, 132 insertions(+), 11 deletions(-)
--
2.51.1
^ permalink raw reply
* [PATCH v5 1/2] dma-mapping: introduce DMA_ATTR_CC_SHARED for shared memory
From: Jiri Pirko @ 2026-03-25 19:23 UTC (permalink / raw)
To: dri-devel, linaro-mm-sig, iommu, linux-media
Cc: sumit.semwal, benjamin.gaignard, Brian.Starkey, jstultz,
tjmercier, christian.koenig, m.szyprowski, robin.murphy, jgg,
leon, sean.anderson, ptesarik, catalin.marinas, aneesh.kumar,
suzuki.poulose, steven.price, thomas.lendacky, john.allen,
ashish.kalra, suravee.suthikulpanit, linux-coco
In-Reply-To: <20260325192352.437608-1-jiri@resnulli.us>
From: Jiri Pirko <jiri@nvidia.com>
Current CC designs don't place a vIOMMU in front of untrusted devices.
Instead, the DMA API forces all untrusted device DMA through swiotlb
bounce buffers (is_swiotlb_force_bounce()) which copies data into
shared memory on behalf of the device.
When a caller has already arranged for the memory to be shared
via set_memory_decrypted(), the DMA API needs to know so it can map
directly using the unencrypted physical address rather than bounce
buffering. Following the pattern of DMA_ATTR_MMIO, add
DMA_ATTR_CC_SHARED for this purpose. Like the MMIO case, only the
caller knows what kind of memory it has and must inform the DMA API
for it to work correctly.
Signed-off-by: Jiri Pirko <jiri@nvidia.com>
---
v4->v5:
- rebased on top od dma-mapping-for-next
- s/decrypted/shared/
v3->v4:
- added some sanity checks to dma_map_phys and dma_unmap_phys
- enhanced documentation of DMA_ATTR_CC_DECRYPTED attr
v1->v2:
- rebased on top of recent dma-mapping-fixes
---
include/linux/dma-mapping.h | 10 ++++++++++
include/trace/events/dma.h | 3 ++-
kernel/dma/direct.h | 14 +++++++++++---
kernel/dma/mapping.c | 13 +++++++++++--
4 files changed, 34 insertions(+), 6 deletions(-)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 677c51ab7510..db8ab24a54f4 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -92,6 +92,16 @@
* flushing.
*/
#define DMA_ATTR_REQUIRE_COHERENT (1UL << 12)
+/*
+ * DMA_ATTR_CC_SHARED: Indicates the DMA mapping is shared (decrypted) for
+ * confidential computing guests. For normal system memory the caller must have
+ * called set_memory_decrypted(), and pgprot_decrypted must be used when
+ * creating CPU PTEs for the mapping. The same shared semantic may be passed
+ * to the vIOMMU when it sets up the IOPTE. For MMIO use together with
+ * DMA_ATTR_MMIO to indicate shared MMIO. Unless DMA_ATTR_MMIO is provided
+ * a struct page is required.
+ */
+#define DMA_ATTR_CC_SHARED (1UL << 13)
/*
* A dma_addr_t can hold any valid DMA or bus address for the platform. It can
diff --git a/include/trace/events/dma.h b/include/trace/events/dma.h
index 63597b004424..31c9ddf72c9d 100644
--- a/include/trace/events/dma.h
+++ b/include/trace/events/dma.h
@@ -34,7 +34,8 @@ TRACE_DEFINE_ENUM(DMA_NONE);
{ DMA_ATTR_PRIVILEGED, "PRIVILEGED" }, \
{ DMA_ATTR_MMIO, "MMIO" }, \
{ DMA_ATTR_DEBUGGING_IGNORE_CACHELINES, "CACHELINES_OVERLAP" }, \
- { DMA_ATTR_REQUIRE_COHERENT, "REQUIRE_COHERENT" })
+ { DMA_ATTR_REQUIRE_COHERENT, "REQUIRE_COHERENT" }, \
+ { DMA_ATTR_CC_SHARED, "CC_SHARED" })
DECLARE_EVENT_CLASS(dma_map,
TP_PROTO(struct device *dev, phys_addr_t phys_addr, dma_addr_t dma_addr,
diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h
index b86ff65496fc..7140c208c123 100644
--- a/kernel/dma/direct.h
+++ b/kernel/dma/direct.h
@@ -89,16 +89,24 @@ static inline dma_addr_t dma_direct_map_phys(struct device *dev,
dma_addr_t dma_addr;
if (is_swiotlb_force_bounce(dev)) {
- if (attrs & (DMA_ATTR_MMIO | DMA_ATTR_REQUIRE_COHERENT))
- return DMA_MAPPING_ERROR;
+ if (!(attrs & DMA_ATTR_CC_SHARED)) {
+ if (attrs & (DMA_ATTR_MMIO | DMA_ATTR_REQUIRE_COHERENT))
+ return DMA_MAPPING_ERROR;
- return swiotlb_map(dev, phys, size, dir, attrs);
+ return swiotlb_map(dev, phys, size, dir, attrs);
+ }
+ } else if (attrs & DMA_ATTR_CC_SHARED) {
+ return DMA_MAPPING_ERROR;
}
if (attrs & DMA_ATTR_MMIO) {
dma_addr = phys;
if (unlikely(!dma_capable(dev, dma_addr, size, false)))
goto err_overflow;
+ } else if (attrs & DMA_ATTR_CC_SHARED) {
+ dma_addr = phys_to_dma_unencrypted(dev, phys);
+ if (unlikely(!dma_capable(dev, dma_addr, size, false)))
+ goto err_overflow;
} else {
dma_addr = phys_to_dma(dev, phys);
if (unlikely(!dma_capable(dev, dma_addr, size, true)) ||
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index df3eccc7d4ca..23ed8eb9233e 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -157,6 +157,7 @@ dma_addr_t dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
{
const struct dma_map_ops *ops = get_dma_ops(dev);
bool is_mmio = attrs & DMA_ATTR_MMIO;
+ bool is_cc_shared = attrs & DMA_ATTR_CC_SHARED;
dma_addr_t addr = DMA_MAPPING_ERROR;
BUG_ON(!valid_dma_direction(dir));
@@ -168,8 +169,11 @@ dma_addr_t dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
return DMA_MAPPING_ERROR;
if (dma_map_direct(dev, ops) ||
- (!is_mmio && arch_dma_map_phys_direct(dev, phys + size)))
+ (!is_mmio && !is_cc_shared &&
+ arch_dma_map_phys_direct(dev, phys + size)))
addr = dma_direct_map_phys(dev, phys, size, dir, attrs, true);
+ else if (is_cc_shared)
+ return DMA_MAPPING_ERROR;
else if (use_dma_iommu(dev))
addr = iommu_dma_map_phys(dev, phys, size, dir, attrs);
else if (ops->map_phys)
@@ -206,11 +210,16 @@ void dma_unmap_phys(struct device *dev, dma_addr_t addr, size_t size,
{
const struct dma_map_ops *ops = get_dma_ops(dev);
bool is_mmio = attrs & DMA_ATTR_MMIO;
+ bool is_cc_shared = attrs & DMA_ATTR_CC_SHARED;
BUG_ON(!valid_dma_direction(dir));
+
if (dma_map_direct(dev, ops) ||
- (!is_mmio && arch_dma_unmap_phys_direct(dev, addr + size)))
+ (!is_mmio && !is_cc_shared &&
+ arch_dma_unmap_phys_direct(dev, addr + size)))
dma_direct_unmap_phys(dev, addr, size, dir, attrs, true);
+ else if (is_cc_shared)
+ return;
else if (use_dma_iommu(dev))
iommu_dma_unmap_phys(dev, addr, size, dir, attrs);
else if (ops->unmap_phys)
--
2.51.1
^ permalink raw reply related
* [PATCH v5 2/2] dma-buf: heaps: system: add system_cc_shared heap for explicitly shared memory
From: Jiri Pirko @ 2026-03-25 19:23 UTC (permalink / raw)
To: dri-devel, linaro-mm-sig, iommu, linux-media
Cc: sumit.semwal, benjamin.gaignard, Brian.Starkey, jstultz,
tjmercier, christian.koenig, m.szyprowski, robin.murphy, jgg,
leon, sean.anderson, ptesarik, catalin.marinas, aneesh.kumar,
suzuki.poulose, steven.price, thomas.lendacky, john.allen,
ashish.kalra, suravee.suthikulpanit, linux-coco
In-Reply-To: <20260325192352.437608-1-jiri@resnulli.us>
From: Jiri Pirko <jiri@nvidia.com>
Add a new "system_cc_shared" dma-buf heap to allow userspace to
allocate shared (decrypted) memory for confidential computing (CoCo)
VMs.
On CoCo VMs, guest memory is private by default. The hardware uses an
encryption bit in page table entries (C-bit on AMD SEV, "shared" bit on
Intel TDX) to control whether a given memory access is private or
shared. The kernel's direct map is set up as private,
so pages returned by alloc_pages() are private in the direct map
by default. To make this memory usable for devices that do not support
DMA to private memory (no TDISP support), it has to be explicitly
shared. A couple of things are needed to properly handle
shared memory for the dma-buf use case:
- set_memory_decrypted() on the direct map after allocation:
Besides clearing the encryption bit in the direct map PTEs, this
also notifies the hypervisor about the page state change. On free,
the inverse set_memory_encrypted() must be called before returning
pages to the allocator. If re-encryption fails, pages
are intentionally leaked to prevent shared memory from being
reused as private.
- pgprot_decrypted() for userspace and kernel virtual mappings:
Any new mapping of the shared pages, be it to userspace via
mmap or to kernel vmalloc space via vmap, creates PTEs independent
of the direct map. These must also have the encryption bit cleared,
otherwise accesses through them would see encrypted (garbage) data.
- DMA_ATTR_CC_SHARED for DMA mapping:
Since the pages are already shared, the DMA API needs to be
informed via DMA_ATTR_CC_SHARED so it can map them correctly
as unencrypted for device access.
On non-CoCo VMs, the system_cc_shared heap is not registered
to prevent misuse by userspace that does not understand
the security implications of explicitly shared memory.
Signed-off-by: Jiri Pirko <jiri@nvidia.com>
---
v4->v5:
- bools renamed: s/decrypted/cc_decrypted/
- other renames: s/decrypted/decrypted/ - this included name of the heap
v2->v3:
- removed couple of leftovers from headers
v1->v2:
- fixed build errors on s390 by including mem_encrypt.h
- converted system heap flag implementation to a separate heap
---
drivers/dma-buf/heaps/system_heap.c | 103 ++++++++++++++++++++++++++--
1 file changed, 98 insertions(+), 5 deletions(-)
diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index b3650d8fd651..03c2b87cb111 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c
@@ -10,17 +10,25 @@
* Andrew F. Davis <afd@ti.com>
*/
+#include <linux/cc_platform.h>
#include <linux/dma-buf.h>
#include <linux/dma-mapping.h>
#include <linux/dma-heap.h>
#include <linux/err.h>
#include <linux/highmem.h>
+#include <linux/mem_encrypt.h>
#include <linux/mm.h>
+#include <linux/set_memory.h>
#include <linux/module.h>
+#include <linux/pgtable.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
+struct system_heap_priv {
+ bool cc_shared;
+};
+
struct system_heap_buffer {
struct dma_heap *heap;
struct list_head attachments;
@@ -29,6 +37,7 @@ struct system_heap_buffer {
struct sg_table sg_table;
int vmap_cnt;
void *vaddr;
+ bool cc_shared;
};
struct dma_heap_attachment {
@@ -36,6 +45,7 @@ struct dma_heap_attachment {
struct sg_table table;
struct list_head list;
bool mapped;
+ bool cc_shared;
};
#define LOW_ORDER_GFP (GFP_HIGHUSER | __GFP_ZERO)
@@ -52,6 +62,34 @@ static gfp_t order_flags[] = {HIGH_ORDER_GFP, HIGH_ORDER_GFP, LOW_ORDER_GFP};
static const unsigned int orders[] = {8, 4, 0};
#define NUM_ORDERS ARRAY_SIZE(orders)
+static int system_heap_set_page_decrypted(struct page *page)
+{
+ unsigned long addr = (unsigned long)page_address(page);
+ unsigned int nr_pages = 1 << compound_order(page);
+ int ret;
+
+ ret = set_memory_decrypted(addr, nr_pages);
+ if (ret)
+ pr_warn_ratelimited("dma-buf system heap: failed to decrypt page at %p\n",
+ page_address(page));
+
+ return ret;
+}
+
+static int system_heap_set_page_encrypted(struct page *page)
+{
+ unsigned long addr = (unsigned long)page_address(page);
+ unsigned int nr_pages = 1 << compound_order(page);
+ int ret;
+
+ ret = set_memory_encrypted(addr, nr_pages);
+ if (ret)
+ pr_warn_ratelimited("dma-buf system heap: failed to re-encrypt page at %p, leaking memory\n",
+ page_address(page));
+
+ return ret;
+}
+
static int dup_sg_table(struct sg_table *from, struct sg_table *to)
{
struct scatterlist *sg, *new_sg;
@@ -90,6 +128,7 @@ static int system_heap_attach(struct dma_buf *dmabuf,
a->dev = attachment->dev;
INIT_LIST_HEAD(&a->list);
a->mapped = false;
+ a->cc_shared = buffer->cc_shared;
attachment->priv = a;
@@ -119,9 +158,11 @@ static struct sg_table *system_heap_map_dma_buf(struct dma_buf_attachment *attac
{
struct dma_heap_attachment *a = attachment->priv;
struct sg_table *table = &a->table;
+ unsigned long attrs;
int ret;
- ret = dma_map_sgtable(attachment->dev, table, direction, 0);
+ attrs = a->cc_shared ? DMA_ATTR_CC_SHARED : 0;
+ ret = dma_map_sgtable(attachment->dev, table, direction, attrs);
if (ret)
return ERR_PTR(ret);
@@ -188,8 +229,13 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
unsigned long addr = vma->vm_start;
unsigned long pgoff = vma->vm_pgoff;
struct scatterlist *sg;
+ pgprot_t prot;
int i, ret;
+ prot = vma->vm_page_prot;
+ if (buffer->cc_shared)
+ prot = pgprot_decrypted(prot);
+
for_each_sgtable_sg(table, sg, i) {
unsigned long n = sg->length >> PAGE_SHIFT;
@@ -206,8 +252,7 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
if (addr + size > vma->vm_end)
size = vma->vm_end - addr;
- ret = remap_pfn_range(vma, addr, page_to_pfn(page),
- size, vma->vm_page_prot);
+ ret = remap_pfn_range(vma, addr, page_to_pfn(page), size, prot);
if (ret)
return ret;
@@ -225,6 +270,7 @@ static void *system_heap_do_vmap(struct system_heap_buffer *buffer)
struct page **pages = vmalloc(sizeof(struct page *) * npages);
struct page **tmp = pages;
struct sg_page_iter piter;
+ pgprot_t prot;
void *vaddr;
if (!pages)
@@ -235,7 +281,10 @@ static void *system_heap_do_vmap(struct system_heap_buffer *buffer)
*tmp++ = sg_page_iter_page(&piter);
}
- vaddr = vmap(pages, npages, VM_MAP, PAGE_KERNEL);
+ prot = PAGE_KERNEL;
+ if (buffer->cc_shared)
+ prot = pgprot_decrypted(prot);
+ vaddr = vmap(pages, npages, VM_MAP, prot);
vfree(pages);
if (!vaddr)
@@ -296,6 +345,14 @@ static void system_heap_dma_buf_release(struct dma_buf *dmabuf)
for_each_sgtable_sg(table, sg, i) {
struct page *page = sg_page(sg);
+ /*
+ * Intentionally leak pages that cannot be re-encrypted
+ * to prevent shared memory from being reused.
+ */
+ if (buffer->cc_shared &&
+ system_heap_set_page_encrypted(page))
+ continue;
+
__free_pages(page, compound_order(page));
}
sg_free_table(table);
@@ -347,6 +404,8 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
unsigned long size_remaining = len;
unsigned int max_order = orders[0];
+ struct system_heap_priv *priv = dma_heap_get_drvdata(heap);
+ bool cc_shared = priv->cc_shared;
struct dma_buf *dmabuf;
struct sg_table *table;
struct scatterlist *sg;
@@ -362,6 +421,7 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
mutex_init(&buffer->lock);
buffer->heap = heap;
buffer->len = len;
+ buffer->cc_shared = cc_shared;
INIT_LIST_HEAD(&pages);
i = 0;
@@ -396,6 +456,14 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
list_del(&page->lru);
}
+ if (cc_shared) {
+ for_each_sgtable_sg(table, sg, i) {
+ ret = system_heap_set_page_decrypted(sg_page(sg));
+ if (ret)
+ goto free_pages;
+ }
+ }
+
/* create the dmabuf */
exp_info.exp_name = dma_heap_get_name(heap);
exp_info.ops = &system_heap_buf_ops;
@@ -413,6 +481,13 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
for_each_sgtable_sg(table, sg, i) {
struct page *p = sg_page(sg);
+ /*
+ * Intentionally leak pages that cannot be re-encrypted
+ * to prevent shared memory from being reused.
+ */
+ if (buffer->cc_shared &&
+ system_heap_set_page_encrypted(p))
+ continue;
__free_pages(p, compound_order(p));
}
sg_free_table(table);
@@ -428,6 +503,14 @@ static const struct dma_heap_ops system_heap_ops = {
.allocate = system_heap_allocate,
};
+static struct system_heap_priv system_heap_priv = {
+ .cc_shared = false,
+};
+
+static struct system_heap_priv system_heap_cc_shared_priv = {
+ .cc_shared = true,
+};
+
static int __init system_heap_create(void)
{
struct dma_heap_export_info exp_info;
@@ -435,8 +518,18 @@ static int __init system_heap_create(void)
exp_info.name = "system";
exp_info.ops = &system_heap_ops;
- exp_info.priv = NULL;
+ exp_info.priv = &system_heap_priv;
+
+ sys_heap = dma_heap_add(&exp_info);
+ if (IS_ERR(sys_heap))
+ return PTR_ERR(sys_heap);
+
+ if (IS_ENABLED(CONFIG_HIGHMEM) ||
+ !cc_platform_has(CC_ATTR_MEM_ENCRYPT))
+ return 0;
+ exp_info.name = "system_cc_shared";
+ exp_info.priv = &system_heap_cc_shared_priv;
sys_heap = dma_heap_add(&exp_info);
if (IS_ERR(sys_heap))
return PTR_ERR(sys_heap);
--
2.51.1
^ permalink raw reply related
* Re: [PATCH v2 3/7] x86/sev: add support for RMPOPT instruction
From: Kalra, Ashish @ 2026-03-25 21:53 UTC (permalink / raw)
To: Andrew Cooper, dave.hansen
Cc: KPrateek.Nayak, Michael.Roth, Nathan.Fontenot, Tycho.Andersen,
aik, ardb, babu.moger, bp, darwi, dave.hansen, davem, dyoung,
herbert, hpa, jackyli, jacobhxu, john.allen, kvm, linux-coco,
linux-crypto, linux-kernel, mingo, nikunj, pawan.kumar.gupta,
pbonzini, peterz, pgonda, rientjes, seanjc, tglx, thomas.lendacky,
x86, xin
In-Reply-To: <4ec520a1-68c7-4833-9e8f-edc610e5fdfa@citrix.com>
On 3/4/2026 9:56 AM, Andrew Cooper wrote:
>>> +/* + * 'val' is a system physical address aligned to 1GB OR'ed with
>>> + * a function selection. Currently supported functions are 0 + *
>>> (verify and report status) and 1 (report status). + */ +static void
>>> rmpopt(void *val) +{ + asm volatile(".byte 0xf2, 0x0f, 0x01, 0xfc" +
>>> : : "a" ((u64)val & PUD_MASK), "c" ((u64)val & 0x1) + : "memory",
>>> "cc"); +}
>> Doesn't this belong in:
>>
>> arch/x86/include/asm/special_insns.h
>>
>> Also, it's not reporting *any* status here, right? So why even talk
>> about it if the kernel isn't doing any status checks? It just makes it
>> more confusing.
>
> The "c" (val & 0x1) constraint encodes whether this is a query or a
> mutation, but both forms produce an answer via the carry flag.
>
> Because it's void, it's a useless helper, and the overloading via one
> parameter makes specifically poor code generation.
RMPOPT instructions for a given 1 GB page can be executed concurrently across CPUs,
reducing the overall penalty of enabling the optimization, hence we use
on_each_cpu_mask() to execute RMPOPT instructions in parallel.
Now, the issue with that is the callback function to run on_each_cpu_mask() is of the type:
(typedef void (*smp_call_func_t)(void *info)).
Hence, the rmpopt() function here has return "void" type and additionally takes "void *"
as parameter.
>
> It should be:
>
> static inline bool __rmpopt(unsigned long addr, unsigned int fn)
> {
> bool res;
>
> asm volatile (".byte 0xf2, 0x0f, 0x01, 0xfc"
> : "=ccc" (res)
> : "a" (addr), "c" (fn));
>
> return res;
> }
>
The above constraints to use on_each_cpu_mask() is forcing the use of:
void rmpopt(void *val)
Thanks,
Ashish
> with:
>
> static inline bool rmpopt_query(unsigned long addr)
> static inline bool rmpopt_set(unsigned long addr)
>
> built on top.
>
> Logic asking hardware to optimise a 1G region because of no guest memory
> should at least WARN() if hardware comes back and says "well hang on now..."
>
> The memory barrier isn't necessary and hinders the optimiser.
>
> ~Andrew
^ permalink raw reply
* Re: [PATCH v2 3/7] x86/sev: add support for RMPOPT instruction
From: Andrew Cooper @ 2026-03-26 0:40 UTC (permalink / raw)
To: Kalra, Ashish, dave.hansen
Cc: Andrew Cooper, KPrateek.Nayak, Michael.Roth, Nathan.Fontenot,
Tycho.Andersen, aik, ardb, babu.moger, bp, darwi, dave.hansen,
davem, dyoung, herbert, hpa, jackyli, jacobhxu, john.allen, kvm,
linux-coco, linux-crypto, linux-kernel, mingo, nikunj,
pawan.kumar.gupta, pbonzini, peterz, pgonda, rientjes, seanjc,
tglx, thomas.lendacky, x86, xin
In-Reply-To: <48f11469-6435-4f3c-ab67-705ad730b042@amd.com>
On 25/03/2026 9:53 pm, Kalra, Ashish wrote:
> On 3/4/2026 9:56 AM, Andrew Cooper wrote:
>> It should be:
>>
>> static inline bool __rmpopt(unsigned long addr, unsigned int fn)
>> {
>> bool res;
>>
>> asm volatile (".byte 0xf2, 0x0f, 0x01, 0xfc"
>> : "=ccc" (res)
>> : "a" (addr), "c" (fn));
>>
>> return res;
>> }
>>
> The above constraints to use on_each_cpu_mask() is forcing the use of:
>
> void rmpopt(void *val)
No. You don't break your thin wrapper in order to force it into a
wrong-shaped hole.
You need something like this:
void do_rmpopt_optimise(void *val)
{
unsigned long addr = *(unsigned long *)val;
WARN_ON_ONCE(__rmpopt(addr, OPTIMISE));
}
to invoke the wrapper safely from the IPI. That will at obvious when
something wrong occurs.
~Andrew
^ permalink raw reply
* Re: [PATCH v13 00/48] arm64: Support for Arm CCA in KVM
From: Gavin Shan @ 2026-03-26 0:48 UTC (permalink / raw)
To: Suzuki K Poulose, Steven Price, Mathieu Poirier
Cc: kvm, kvmarm, Catalin Marinas, Marc Zyngier, Will Deacon,
James Morse, Oliver Upton, 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
In-Reply-To: <9247d9ea-64b4-4e8e-81f8-3c8e00750acf@arm.com>
Hi Suzuki,
On 3/25/26 8:16 PM, Suzuki K Poulose wrote:
> On 25/03/2026 06:37, Gavin Shan wrote:
>> On 3/21/26 2:45 AM, Steven Price wrote:
[...]
>>
>> In upstream TF-A repository [1], I don't see the config option 'RMM_V1_COMPAT'.
>> would it be something else?
>>
>> [1] git@github.com:ARM-software/arm-trusted-firmware.git (branch: master)
>>
>
> suzuki@ewhatever:trusted-firmware-a$ git grep RMM_V1_COMPAT
> Makefile: RMM_V1_COMPAT \
> Makefile: RMM_V1_COMPAT \
> docs/getting_started/build-options.rst:- ``RMM_V1_COMPAT``: Boolean flag to enable support for RMM v1.x compatibility
> include/services/rmmd_svc.h:#if RMM_V1_COMPAT
> include/services/rmmd_svc.h:#endif /* RMM_V1_COMPAT */
> make_helpers/defaults.mk:RMM_V1_COMPAT := 1
> services/std_svc/rmmd/rmmd_main.c:#if RMM_V1_COMPAT
> services/std_svc/rmmd/rmmd_main.c:#if RMM_V1_COMPAT
> services/std_svc/rmmd/rmmd_main.c:#if !RMM_V1_COMPAT
> services/std_svc/rmmd/rmmd_main.c:#if RMM_V1_COMPAT
> services/std_svc/rmmd/rmmd_main.c:#if RMM_V1_COMPAT
> services/std_svc/rmmd/rmmd_main.c:#if RMM_V1_COMPAT
> services/std_svc/rmmd/rmmd_rmm_lfa.c:#if RMM_V1_COMPAT
> services/std_svc/rmmd/rmmd_rmm_lfa.c:#if RMM_V1_COMPAT
> services/std_svc/rmmd/rmmd_rmm_lfa.c:#if RMM_V1_COMPAT
> services/std_svc/rmmd/rmmd_rmm_lfa.c:#if RMM_V1_COMPAT
> suzuki@ewhatever:trusted-firmware-a$ git log --oneline -1
> 8dae0862c (HEAD, origin/master, origin/integration, origin/HEAD) Merge changes from topic "qti_lemans_evk" into integration
> suzuki@ewhatever:trusted-firmware-a$ git remote get-url origin
> https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
>
Thanks for the details. It turned out that I used the wrong TF-A repository. In
the proposed repository, I'm able to see the option 'RMM_V1_COMPAT' and the EL3-RMM
interface compatible issue disappears. However, there are more issues popped up.
I build everything manually where the host is emulated by QEMU instead of shrinkwrap
and FVP model. It's used to work well before. Maybe it's time to switch to shinkwrap
and FVP model since device assignment (DA) isn't supported by an emulated host
by QEMU and shrinkwrap and FVP model seems the only option. I need to learn how
to do that later.
There are two issues I can see with the following combinations. Details are provided
like below.
QEMU: https://git.qemu.org/git/qemu.git (branch: stable-9.2)
TF-RMM: https://git.trustedfirmware.org/TF-RMM/tf-rmm.git (branch: topics/rmm-v2.0-poc)
EDK2: git@github.com:tianocore/edk2.git (tag: edk2-stable202411)
TF-A: https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git (branch: master)
HOST: https://git.gitlab.arm.com/linux-arm/linux-cca.git (branch: cca-host/v13)
BUILDROOT: https://github.com/buildroot/buildroot (branch: master)
KVMTOOL: https://gitlab.arm.com/linux-arm/kvmtool-cca (branch: cca/v11)
GUEST: https://github.com/torvalds/linux.git (branch: master)
(1) The emulated host is started by the following command lines.
sudo /home/gshan/sandbox/cca/host/qemu/build/qemu-system-aarch64 \
-M virt,virtualization=on,secure=on,gic-version=3,acpi=off \
-cpu max,x-rme=on -m 8G -smp 8 \
-serial mon:stdio -monitor none -nographic -nodefaults \
-bios /home/gshan/sandbox/cca/host/tf-a/flash.bin \
-kernel /home/gshan/sandbox/cca/host/linux/arch/arm64/boot/Image \
-initrd /home/gshan/sandbox/cca/host/buildroot/output/images/rootfs.cpio.xz \
-device pcie-root-port,bus=pcie.0,chassis=1,id=pcie.1 \
-device pcie-root-port,bus=pcie.0,chassis=2,id=pcie.2 \
-device pcie-root-port,bus=pcie.0,chassis=3,id=pcie.3 \
-device pcie-root-port,bus=pcie.0,chassis=4,id=pcie.4 \
-device virtio-9p-device,fsdev=shr0,mount_tag=shr0 \
-fsdev local,security_model=none,path=/home/gshan/sandbox/cca/guest,id=shr0 \
-netdev tap,id=tap1,script=/etc/qemu-ifup-gshan,downscript=/etc/qemu-ifdown-gshan \
-device virtio-net-pci,bus=pcie.2,netdev=tap1,mac=b8:3f:d2:1d:3e:f1
(2) Issue-1: TF-RMM complains about the root complex list is invalid. This error is
raised in TF-RMM::setup_root_complex_list() where the error code is still set to
0 (SUCCESS) in this failing case. The TF-RMM initialization is terminated early,
but TF-A still thinks the initialization has been completely done.
INFO: BL31: Initializing RMM
INFO: RMM init start.
RMM EL3 compat memory reservation enabled.
Dynamic VA pool base address: 0xc0000000
Reserved 20 pages. Remaining: 3615 pages
Reserve mem: 20 pages at PA: 0x401f2000 (alignment 0x1000)
Static Low VA initialized. xlat tables allocated: 20 used: 7
Reserved 514 pages. Remaining: 3101 pages
Reserve mem: 514 pages at PA: 0x40206000 (alignment 0x1000)
Dynamic Low VA initialized. xlat tables allocated: 514 used: 514
Invalid: Root Complex list <<<<< ERROR
INFO: RMM init end.
(3) Issue-2: The host kernel gets stuck in rmi_check_version() where SMC_RMI_VERSION
is issued to TF-A, but it can't be forwarded to TF-RMM because its initialization
isn't completely done (issue-1).
[ 37.438253] Unpacking initramfs...
[ 37.563460] kvm [1]: nv: 570 coarse grained trap handlers
[ 37.581139] kvm [1]: nv: 664 fine grained trap handlers
<... system becomes stuck here ...>
So my workaround is to skip fetching root complex list from the EL3-RMM manifest data
in TF-RMM::setup_root_complex_list() since it's not provided for the qemu platform by
TF-A. With this workaround, the host can boot up into shell prompt and the guest can
be started by kvmtool.
host$ uname -r
7.0.0-rc1-gavin-gd62aa44b2590
host$ lkvm run --realm -c 2 -m 256 \
-k /mnt/linux/arch/arm64/boot/Image \
-i /mnt/buildroot/output/images/rootfs.cpio.xz
-p earlycon=uart,mmio,0x101000000
Info: # lkvm run -k /mnt/linux/arch/arm64/boot/Image -m 256 -c 2 --name guest-163
Info: Enabling Guest memfd for confidential guest
Warning: The maximum recommended amount of VCPUs is 1
[ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x000f0510]
[ 0.000000] Linux version 7.0.0-rc2-gavin-g0031c06807cf (gshan@nvidia-grace-hopper-01.khw.eng.bos2.dc.redhat.com) (gcc (GCC) 14.3.1 20251022 (Red Hat 14.3.1-4), GNU ld version 2.41-64.el10) #2 SMP PREEMPT Wed Mar 25 20:28:05 EDT 2026
[ 0.000000] KASLR enabled
:
[ 267.578060] Freeing initrd memory: 4728K
[ 267.921865] Warning: unable to open an initial console.
[ 270.327960] Freeing unused kernel memory: 1792K
[ 270.669368] Run /init as init process
Thanks,
Gavin
^ permalink raw reply
* Re: [PATCH v2 03/19] device core: Introduce confidential device acceptance
From: Dan Williams @ 2026-03-26 1:27 UTC (permalink / raw)
To: Jason Gunthorpe, Dan Williams
Cc: Greg KH, linux-coco, linux-pci, aik, aneesh.kumar, yilun.xu,
bhelgaas, alistair23, lukas, Christoph Hellwig, Marek Szyprowski,
Robin Murphy, Roman Kisel, Samuel Ortiz, Rafael J. Wysocki,
Danilo Krummrich
In-Reply-To: <20260325115607.GB67624@nvidia.com>
Jason Gunthorpe wrote:
[..]
> > Right, the potential to see in-between states concerns me because TSM
> > uAPIs would have fully enabled the device to wreak havoc, meanwhile
> > dev->trust is still showing the device at some lower level of trust. So
> > I think trust modification needs to be synchronous with privileges
> > granted/revoked.
>
> If an iommu is present then the device will still be blocked even
> though it is in RUN, I'm not sure this synchronicity is so important.
Oh, maybe we are just quibbling about where the mechanism lives. The
"unblock DMA" step in current preliminary patches is currently behind
the "struct pci_tsm_ops::accept()" op which also handles transitioning
the device to RUN / T=1. It is a bus callback.
However, if the IOMMU layer is enlightened to block/unblock DMA on trust
setting then the TDISP "unblock DMA" step can be factored out of this bus
callback and into the IOMMU trust responder.
So device could enter T=1 way in advance of the "unblock DMA" event.
I assume this would also expect that encrypted MMIO mappings are also
not established while trust is less than "TCB"? That would require some
additional enabling to catch attempts to establish an encrypted mapping
that the hardware is prepared for, but dev->trust is not, all without
needing to modify the driver to worry about this difference. Drivers
would just see ioremap() failure in this case.
A bit more work, but yes, that is a cleaner separation of concerns.
^ permalink raw reply
* Re: [PATCH v2 3/7] x86/sev: add support for RMPOPT instruction
From: Kalra, Ashish @ 2026-03-26 2:02 UTC (permalink / raw)
To: Andrew Cooper, dave.hansen
Cc: KPrateek.Nayak, Michael.Roth, Nathan.Fontenot, Tycho.Andersen,
aik, ardb, babu.moger, bp, darwi, dave.hansen, davem, dyoung,
herbert, hpa, jackyli, jacobhxu, john.allen, kvm, linux-coco,
linux-crypto, linux-kernel, mingo, nikunj, pawan.kumar.gupta,
pbonzini, peterz, pgonda, rientjes, seanjc, tglx, thomas.lendacky,
x86, xin
In-Reply-To: <dc8d4117-3089-48bb-8911-b4d64481fc44@citrix.com>
On 3/25/2026 7:40 PM, Andrew Cooper wrote:
> On 25/03/2026 9:53 pm, Kalra, Ashish wrote:
>> On 3/4/2026 9:56 AM, Andrew Cooper wrote:
>>> It should be:
>>>
>>> static inline bool __rmpopt(unsigned long addr, unsigned int fn)
>>> {
>>> bool res;
>>>
>>> asm volatile (".byte 0xf2, 0x0f, 0x01, 0xfc"
>>> : "=ccc" (res)
>>> : "a" (addr), "c" (fn));
>>>
>>> return res;
>>> }
>>>
>> The above constraints to use on_each_cpu_mask() is forcing the use of:
>>
>> void rmpopt(void *val)
>
> No. You don't break your thin wrapper in order to force it into a
> wrong-shaped hole.
>
> You need something like this:
>
> void do_rmpopt_optimise(void *val)
> {
> unsigned long addr = *(unsigned long *)val;
>
> WARN_ON_ONCE(__rmpopt(addr, OPTIMISE));
> }
>
> to invoke the wrapper safely from the IPI. That will at obvious when
> something wrong occurs.
This wrapper i can/will use, but doing a WARN_ON_ONCE() is probably avoidable as
there will be ranges where RMPOPT will always fail, such as while checking
the RMP table entries itself, so there is a good chance that we will always trigger
the WARN_ON_ONCE() on the memory range containing the RMP table.
Thanks,
Ashish
>
> ~Andrew
^ permalink raw reply
* Re: [PATCH v2 3/7] x86/sev: add support for RMPOPT instruction
From: Kalra, Ashish @ 2026-03-26 2:14 UTC (permalink / raw)
To: Andrew Cooper, dave.hansen
Cc: KPrateek.Nayak, Michael.Roth, Nathan.Fontenot, Tycho.Andersen,
aik, ardb, babu.moger, bp, darwi, dave.hansen, davem, dyoung,
herbert, hpa, jackyli, jacobhxu, john.allen, kvm, linux-coco,
linux-crypto, linux-kernel, mingo, nikunj, pawan.kumar.gupta,
pbonzini, peterz, pgonda, rientjes, seanjc, tglx, thomas.lendacky,
x86, xin
In-Reply-To: <4698d9ba-7030-4447-89c0-c992b776377b@amd.com>
On 3/25/2026 9:02 PM, Kalra, Ashish wrote:
>
> On 3/25/2026 7:40 PM, Andrew Cooper wrote:
>> On 25/03/2026 9:53 pm, Kalra, Ashish wrote:
>>> On 3/4/2026 9:56 AM, Andrew Cooper wrote:
>>>> It should be:
>>>>
>>>> static inline bool __rmpopt(unsigned long addr, unsigned int fn)
>>>> {
>>>> bool res;
>>>>
>>>> asm volatile (".byte 0xf2, 0x0f, 0x01, 0xfc"
>>>> : "=ccc" (res)
>>>> : "a" (addr), "c" (fn));
>>>>
>>>> return res;
>>>> }
>>>>
>>> The above constraints to use on_each_cpu_mask() is forcing the use of:
>>>
>>> void rmpopt(void *val)
>>
>> No. You don't break your thin wrapper in order to force it into a
>> wrong-shaped hole.
>>
>> You need something like this:
>>
>> void do_rmpopt_optimise(void *val)
>> {
>> unsigned long addr = *(unsigned long *)val;
>>
>> WARN_ON_ONCE(__rmpopt(addr, OPTIMISE));
>> }
>>
>> to invoke the wrapper safely from the IPI. That will at obvious when
>> something wrong occurs.
>
> This wrapper i can/will use, but doing a WARN_ON_ONCE() is probably avoidable as
> there will be ranges where RMPOPT will always fail, such as while checking
> the RMP table entries itself, so there is a good chance that we will always trigger
> the WARN_ON_ONCE() on the memory range containing the RMP table.
>
To add, the above is in context of the current implementation, where we scan all
memory up-to 2TB for applying RMP optimizations when SNP is enabled (and/or SNP_INIT).
We will *always* get this stack trace during booting, so i think it makes sense
to avoid this WARN_ON_ONCE().
Thanks,
Ashish
^ permalink raw reply
* [PATCH v6 02/22] coco/tdx-host: Introduce a "tdx_host" device
From: Chao Gao @ 2026-03-26 8:43 UTC (permalink / raw)
To: linux-kernel, linux-coco, kvm
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Jonathan Cameron,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
H. Peter Anvin
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
TDX depends on a platform firmware module that is invoked via instructions
similar to vmenter (i.e. enter into a new privileged "root-mode" context to
manage private memory and private device mechanisms). It is a software
construct that depends on the CPU vmxon state to enable invocation of
TDX module ABIs. Unlike other Trusted Execution Environment (TEE) platform
implementations that employ a firmware module running on a PCI device with
an MMIO mailbox for communication, TDX has no hardware device to point to
as the TEE Secure Manager (TSM).
Create a virtual device not only to align with other implementations but
also to make it easier to
- expose metadata (e.g., TDX module version, seamldr version etc) to
the userspace as device attributes
- implement firmware uploader APIs which are tied to a device. This is
needed to support TDX module runtime updates
- enable TDX Connect which will share a common infrastructure with other
platform implementations. In the TDX Connect context, every
architecture has a TSM, represented by a PCIe or virtual device. The
new "tdx_host" device will serve the TSM role.
A faux device is used for TDX because the TDX module is singular within
the system and lacks associated platform resources. Using a faux device
eliminates the need to create a stub bus.
The call to tdx_get_sysinfo() ensures that the TDX module is ready to
provide services.
Note that AMD has a PCI device for the PSP for SEV and ARM CCA will
likely have a faux device [1].
Co-developed-by: Xu Yilun <yilun.xu@linux.intel.com>
Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Link: https://lore.kernel.org/all/2025073035-bulginess-rematch-b92e@gregkh/ # [1]
---
v3:
- add Jonathan's reviewed-by
- add tdx_get_sysinfo() in module_init() to ensure the TDX module is up
and running.
- note in the changelog that both AMD and ARM have devices for coco
---
arch/x86/virt/vmx/tdx/tdx.c | 2 +-
drivers/virt/coco/Kconfig | 2 ++
drivers/virt/coco/Makefile | 1 +
drivers/virt/coco/tdx-host/Kconfig | 10 +++++++
drivers/virt/coco/tdx-host/Makefile | 1 +
drivers/virt/coco/tdx-host/tdx-host.c | 43 +++++++++++++++++++++++++++
6 files changed, 58 insertions(+), 1 deletion(-)
create mode 100644 drivers/virt/coco/tdx-host/Kconfig
create mode 100644 drivers/virt/coco/tdx-host/Makefile
create mode 100644 drivers/virt/coco/tdx-host/tdx-host.c
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 06d9709ade85..172f6d4133b5 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1435,7 +1435,7 @@ const struct tdx_sys_info *tdx_get_sysinfo(void)
return p;
}
-EXPORT_SYMBOL_FOR_KVM(tdx_get_sysinfo);
+EXPORT_SYMBOL_FOR_MODULES(tdx_get_sysinfo, "kvm-intel,tdx-host");
u32 tdx_get_nr_guest_keyids(void)
{
diff --git a/drivers/virt/coco/Kconfig b/drivers/virt/coco/Kconfig
index df1cfaf26c65..f7691f64fbe3 100644
--- a/drivers/virt/coco/Kconfig
+++ b/drivers/virt/coco/Kconfig
@@ -17,5 +17,7 @@ source "drivers/virt/coco/arm-cca-guest/Kconfig"
source "drivers/virt/coco/guest/Kconfig"
endif
+source "drivers/virt/coco/tdx-host/Kconfig"
+
config TSM
bool
diff --git a/drivers/virt/coco/Makefile b/drivers/virt/coco/Makefile
index cb52021912b3..b323b0ae4f82 100644
--- a/drivers/virt/coco/Makefile
+++ b/drivers/virt/coco/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_EFI_SECRET) += efi_secret/
obj-$(CONFIG_ARM_PKVM_GUEST) += pkvm-guest/
obj-$(CONFIG_SEV_GUEST) += sev-guest/
obj-$(CONFIG_INTEL_TDX_GUEST) += tdx-guest/
+obj-$(CONFIG_INTEL_TDX_HOST) += tdx-host/
obj-$(CONFIG_ARM_CCA_GUEST) += arm-cca-guest/
obj-$(CONFIG_TSM) += tsm-core.o
obj-$(CONFIG_TSM_GUEST) += guest/
diff --git a/drivers/virt/coco/tdx-host/Kconfig b/drivers/virt/coco/tdx-host/Kconfig
new file mode 100644
index 000000000000..d35d85ef91c0
--- /dev/null
+++ b/drivers/virt/coco/tdx-host/Kconfig
@@ -0,0 +1,10 @@
+config TDX_HOST_SERVICES
+ tristate "TDX Host Services Driver"
+ depends on INTEL_TDX_HOST
+ default m
+ help
+ Enable access to TDX host services like module update and
+ extensions (e.g. TDX Connect).
+
+ Say y or m if enabling support for confidential virtual machine
+ support (CONFIG_INTEL_TDX_HOST). The module is called tdx_host.ko.
diff --git a/drivers/virt/coco/tdx-host/Makefile b/drivers/virt/coco/tdx-host/Makefile
new file mode 100644
index 000000000000..e61e749a8dff
--- /dev/null
+++ b/drivers/virt/coco/tdx-host/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_TDX_HOST_SERVICES) += tdx-host.o
diff --git a/drivers/virt/coco/tdx-host/tdx-host.c b/drivers/virt/coco/tdx-host/tdx-host.c
new file mode 100644
index 000000000000..c77885392b09
--- /dev/null
+++ b/drivers/virt/coco/tdx-host/tdx-host.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * TDX host user interface driver
+ *
+ * Copyright (C) 2025 Intel Corporation
+ */
+
+#include <linux/device/faux.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+
+#include <asm/cpu_device_id.h>
+#include <asm/tdx.h>
+
+static const struct x86_cpu_id tdx_host_ids[] = {
+ X86_MATCH_FEATURE(X86_FEATURE_TDX_HOST_PLATFORM, NULL),
+ {}
+};
+MODULE_DEVICE_TABLE(x86cpu, tdx_host_ids);
+
+static struct faux_device *fdev;
+
+static int __init tdx_host_init(void)
+{
+ if (!x86_match_cpu(tdx_host_ids) || !tdx_get_sysinfo())
+ return -ENODEV;
+
+ fdev = faux_device_create(KBUILD_MODNAME, NULL, NULL);
+ if (!fdev)
+ return -ENODEV;
+
+ return 0;
+}
+module_init(tdx_host_init);
+
+static void __exit tdx_host_exit(void)
+{
+ faux_device_destroy(fdev);
+}
+module_exit(tdx_host_exit);
+
+MODULE_DESCRIPTION("TDX Host Services");
+MODULE_LICENSE("GPL");
--
2.47.3
^ permalink raw reply related
* [PATCH v6 00/22] Runtime TDX module update support
From: Chao Gao @ 2026-03-26 8:43 UTC (permalink / raw)
To: kvm, linux-coco, linux-doc, linux-kernel, linux-rt-devel, x86
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Borislav Petkov,
Clark Williams, H. Peter Anvin, Ingo Molnar, Jonathan Corbet,
Sebastian Andrzej Siewior, Shuah Khan, Steven Rostedt,
Thomas Gleixner
Hi Reviewers,
Please review patches 6 and 17; others already have 2+ RB tags.
Patch 6 was reworked to use is_visible() for attribute visibility (which is
the standard practice), so previous RB tags were dropped. Patch 17 has
fewer reviews so far and needs another look.
I believe this series is quite mature and also self-contained (no impact to
the rest of kernel unless an update is triggered through the dedicated
sysfs ABIs). I'm hoping it can be merged for 7.1.
Changelog:
v5->v6:
- use TDX_VERSION_FMT macro [Dave/Kiryl]
- use is_visible() to control seamldr attribute visibility [Yilun]
- drop revision/chapter numbers when referring to a spec [Kiryl/Xiaoyao]
- change update failure indicator from int to boolean [Kiryl]
- reset tdx_lp_initialized for offlined CPUs [Kai]
- add a wrapper for seamldr_call(P_SEAMLDR_INSTALL..) [Kiryl]
- clarify the "do nothing" choice when collision detection isn't
supported [Kai/Kiryl]
- other minor code changes, changelog improvements and typo fixes [Kiryl/Kai/Xiaoyao]
- collect review tags from Kiryl/Kai
- v5: https://lore.kernel.org/kvm/20260315135920.354657-1-chao.gao@intel.com/
(For transparency, note that I used AI tools to help proofread this
cover-letter and commit messages)
This series adds support for runtime TDX module updates that preserve
running TDX guests. It is also available at:
https://github.com/gaochaointel/linux-dev/commits/tdx-module-updates-v6/
== Background ==
Intel TDX isolates Trusted Domains (TDs), or confidential guests, from the
host. A key component of Intel TDX is the TDX module, which enforces
security policies to protect the memory and CPU states of TDs from the
host. However, the TDX module is software that requires updates.
== Problems ==
Currently, the TDX module is loaded by the BIOS at boot time, and the only
way to update it is through a reboot, which results in significant system
downtime. Users expect the TDX module to be updatable at runtime without
disrupting TDX guests.
== Solution ==
On TDX platforms, P-SEAMLDR[1] is a component within the protected SEAM
range. It is loaded by the BIOS and provides the host with functions to
install a TDX module at runtime.
Implement a TDX module update facility via the fw_upload mechanism. Given
that there is variability in which module update to load based on features,
fix levels, and potentially reloading the same version for error recovery
scenarios, the explicit userspace chosen payload flexibility of fw_upload
is attractive.
This design allows the kernel to accept a bitstream instead of loading a
named file from the filesystem, as the module selection and policy
enforcement for TDX modules are quite complex (see patch "coco/tdx-host:
Implement firmware upload sysfs ABI for TDX module updates"). By doing
so, much of this complexity is shifted out of the kernel. The kernel
needs to expose information, such as the TDX module version, to
userspace. Userspace must understand the TDX module versioning scheme
and update policy to select the appropriate TDX module (see "TDX module
Versioning" below).
In the unlikely event the update fails, for example userspace picks an
incompatible update image, or the image is otherwise corrupted, all TDs
will experience SEAMCALL failures and be killed. The recovery of TD
operation from that event requires a reboot.
Given there is no mechanism to quiesce SEAMCALLs, the TDs themselves must
pause execution over an update. The most straightforward way to meet the
'pause TDs while update executes' constraint is to run the update in
stop_machine() context. All other evaluated solutions export more
complexity to KVM, or exports more fragility to userspace.
== How to test this series ==
First, load kvm-intel.ko and tdx-host.ko if they haven't been loaded:
# modprobe -r kvm_intel
# modprobe kvm_intel tdx=1
# modprobe tdx-host
Then, use the userspace tool below to select the appropriate TDX module and
install it via the interfaces exposed by this series:
# git clone https://github.com/intel/tdx-module-binaries
# cd tdx-module-binaries
# python version_select_and_load.py --update
this version changes the firmware directory name from seamldr_upload to
tdx_module, so, below change should be applied to version_select_and_load.py:
diff --git a/version_select_and_load.py b/version_select_and_load.py
index 2193bd8..6a3b604 100644
--- a/version_select_and_load.py
+++ b/version_select_and_load.py
@@ -38,7 +38,7 @@ except ImportError:
print("Error: cpuid module is not installed. Please install it using 'pip install cpuid'")
sys.exit(1)
-FIRMWARE_PATH = "/sys/class/firmware/seamldr_upload"
+FIRMWARE_PATH = "/sys/class/firmware/tdx_module"
MODULE_PATH = "/sys/devices/faux/tdx_host"
SEAMLDR_PATH = "/sys/devices/faux/tdx_host/seamldr"
allow_debug = False
== Other information relevant to Runtime TDX module updates ==
=== TDX module versioning ===
Each TDX module is assigned a version number x.y.z, where x represents the
"major" version, y the "minor" version, and z the "update" version.
Runtime TDX module updates are restricted to Z-stream releases.
Note that Z-stream releases do not necessarily guarantee compatibility. A
new release may not be compatible with all previous versions. To address this,
Intel provides a separate file containing compatibility information, which
specifies the minimum module version required for a particular update. This
information is referenced by the tool to determine if two modules are
compatible.
=== TCB Stability ===
Updates change the TCB as viewed by attestation reports. In TDX there is
a distinction between launch-time version and current version where
runtime TDX module updates cause that latter version number to change,
subject to Z-stream constraints.
The concern that a malicious host may attack confidential VMs by loading
insecure updates was addressed by Alex in [3]. Similarly, the scenario
where some "theoretical paranoid tenant" in the cloud wants to audit
updates and stop trusting the host after updates until audit completion
was also addressed in [4]. Users not in the cloud control the host machine
and can manage updates themselves, so they don't have these concerns.
See more about the implications of current TCB version changes in
attestation as summarized by Dave in [5].
=== TDX module Distribution Model ===
At a high level, Intel publishes all TDX modules on the github [2], along
with a mapping_file.json which documents the compatibility information
about each TDX module and a userspace tool to install the TDX module. OS
vendors can package these modules and distribute them. Administrators
install the package and use the tool to select the appropriate TDX module
and install it via the interfaces exposed by this series.
[1]: https://cdrdv2.intel.com/v1/dl/getContent/733584
[2]: https://github.com/intel/tdx-module-binaries
[3]: https://lore.kernel.org/all/665c5ae0-4b7c-4852-8995-255adf7b3a2f@amazon.com/
[4]: https://lore.kernel.org/all/5d1da767-491b-4077-b472-2cc3d73246d6@amazon.com/
[5]: https://lore.kernel.org/all/94d6047e-3b7c-4bc1-819c-85c16ff85abf@intel.com/
Chao Gao (21):
coco/tdx-host: Introduce a "tdx_host" device
coco/tdx-host: Expose TDX module version
x86/virt/seamldr: Introduce a wrapper for P-SEAMLDR SEAMCALLs
x86/virt/seamldr: Add a helper to retrieve P-SEAMLDR information
coco/tdx-host: Expose P-SEAMLDR information via sysfs
coco/tdx-host: Implement firmware upload sysfs ABI for TDX module
updates
x86/virt/seamldr: Allocate and populate a module update request
x86/virt/seamldr: Introduce skeleton for TDX module updates
x86/virt/seamldr: Abort updates if errors occurred midway
x86/virt/seamldr: Shut down the current TDX module
x86/virt/tdx: Reset software states during TDX module shutdown
x86/virt/seamldr: Install a new TDX module
x86/virt/seamldr: Do TDX per-CPU initialization after updates
x86/virt/tdx: Restore TDX module state
x86/virt/tdx: Update tdx_sysinfo and check features post-update
x86/virt/tdx: Avoid updates during update-sensitive operations
coco/tdx-host: Don't expose P-SEAMLDR features on CPUs with erratum
x86/virt/tdx: Enable TDX module runtime updates
coco/tdx-host: Document TDX module update compatibility criteria
x86/virt/tdx: Document TDX module update
x86/virt/seamldr: Log TDX module update failures
Kai Huang (1):
x86/virt/tdx: Move low level SEAMCALL helpers out of <asm/tdx.h>
.../ABI/testing/sysfs-devices-faux-tdx-host | 75 ++++
Documentation/arch/x86/tdx.rst | 36 ++
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/include/asm/seamldr.h | 37 ++
arch/x86/include/asm/tdx.h | 64 +---
arch/x86/include/asm/tdx_global_metadata.h | 5 +
arch/x86/include/asm/vmx.h | 1 +
arch/x86/kvm/vmx/tdx_errno.h | 2 -
arch/x86/virt/vmx/tdx/Makefile | 2 +-
arch/x86/virt/vmx/tdx/seamcall_internal.h | 109 ++++++
arch/x86/virt/vmx/tdx/seamldr.c | 335 ++++++++++++++++++
arch/x86/virt/vmx/tdx/tdx.c | 166 ++++++---
arch/x86/virt/vmx/tdx/tdx.h | 11 +-
arch/x86/virt/vmx/tdx/tdx_global_metadata.c | 20 ++
drivers/virt/coco/Kconfig | 2 +
drivers/virt/coco/Makefile | 1 +
drivers/virt/coco/tdx-host/Kconfig | 12 +
drivers/virt/coco/tdx-host/Makefile | 1 +
drivers/virt/coco/tdx-host/tdx-host.c | 250 +++++++++++++
19 files changed, 1027 insertions(+), 103 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-devices-faux-tdx-host
create mode 100644 arch/x86/include/asm/seamldr.h
create mode 100644 arch/x86/virt/vmx/tdx/seamcall_internal.h
create mode 100644 arch/x86/virt/vmx/tdx/seamldr.c
create mode 100644 drivers/virt/coco/tdx-host/Kconfig
create mode 100644 drivers/virt/coco/tdx-host/Makefile
create mode 100644 drivers/virt/coco/tdx-host/tdx-host.c
base-commit: 0f409eaea53e49932cf92a761de66345c9a4b4be
--
2.47.3
^ permalink raw reply related
* [PATCH v6 05/22] x86/virt/seamldr: Add a helper to retrieve P-SEAMLDR information
From: Chao Gao @ 2026-03-26 8:43 UTC (permalink / raw)
To: linux-kernel, linux-coco, kvm
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, x86, H. Peter Anvin
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
P-SEAMLDR returns its information such as version number, in response to
the SEAMLDR.INFO SEAMCALL.
This information is useful for userspace. For example, the admin can decide
which TDX module versions are compatible with the P-SEAMLDR according to
the P-SEAMLDR version.
Add a helper to retrieve P-SEAMLDR information in preparation for
exposing P-SEAMLDR version and other necessary information to userspace.
Export the new kAPI for use by tdx-host.ko.
Note that there are two distinct P-SEAMLDR APIs with similar names:
SEAMLDR.INFO: Returns a SEAMLDR_INFO structure containing SEAMLDR
information such as version and remaining updates.
SEAMLDR.SEAMINFO: Returns a SEAMLDR_SEAMINFO structure containing SEAM
and system information such as Convertible Memory
Regions (CMRs) and number of CPUs and sockets.
The former is used here.
For details, see "Intel® Trust Domain Extensions - SEAM Loader (SEAMLDR)
Interface Specification" revision 343755-003.
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
---
v6:
- Clarify that this patch introduces a helper for retrieving info, not
the retrieval itself [Xiaoyao]
v5:
- add a comment for slow_virt_to_phys() [Kai]
v4:
- put seamldr_info on stack [Dave]
- improve changelogs to explain SEAMLDR.INFO and SEAMLDR.SEAMINFO [Dave]
- add P-SEAMLDR spec information in the changelog [Dave]
- add proper comments above ABI structure definition [Dave]
- add unused ABI structure fields rather than marking them as reserved
to better align with the specc [Dave] (I omitted "not used by kernel"
tags since there are 5-6 such fields and maintaining these tags would
be tedious.)
---
arch/x86/include/asm/seamldr.h | 36 +++++++++++++++++++++++++++++++++
arch/x86/virt/vmx/tdx/seamldr.c | 19 ++++++++++++++++-
2 files changed, 54 insertions(+), 1 deletion(-)
create mode 100644 arch/x86/include/asm/seamldr.h
diff --git a/arch/x86/include/asm/seamldr.h b/arch/x86/include/asm/seamldr.h
new file mode 100644
index 000000000000..c67e5bc910a9
--- /dev/null
+++ b/arch/x86/include/asm/seamldr.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_SEAMLDR_H
+#define _ASM_X86_SEAMLDR_H
+
+#include <linux/types.h>
+
+/*
+ * This is called the "SEAMLDR_INFO" data structure and is defined
+ * in "SEAM Loader (SEAMLDR) Interface Specification".
+ *
+ * The SEAMLDR.INFO documentation requires this to be aligned to a
+ * 256-byte boundary.
+ */
+struct seamldr_info {
+ u32 version;
+ u32 attributes;
+ u32 vendor_id;
+ u32 build_date;
+ u16 build_num;
+ u16 minor_version;
+ u16 major_version;
+ u16 update_version;
+ u32 acm_x2apicid;
+ u32 num_remaining_updates;
+ u8 seam_info[128];
+ u8 seam_ready;
+ u8 seam_debug;
+ u8 p_seam_ready;
+ u8 reserved[93];
+} __packed __aligned(256);
+
+static_assert(sizeof(struct seamldr_info) == 256);
+
+int seamldr_get_info(struct seamldr_info *seamldr_info);
+
+#endif /* _ASM_X86_SEAMLDR_H */
diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index 65616dd2f4d2..8410df3a0bf4 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -8,8 +8,13 @@
#include <linux/spinlock.h>
+#include <asm/seamldr.h>
+
#include "seamcall_internal.h"
+/* P-SEAMLDR SEAMCALL leaf function */
+#define P_SEAMLDR_INFO 0x8000000000000000
+
/*
* Serialize P-SEAMLDR calls since the hardware only allows a single CPU to
* interact with P-SEAMLDR simultaneously. Use raw version as the calls can
@@ -18,8 +23,20 @@
*/
static DEFINE_RAW_SPINLOCK(seamldr_lock);
-static __maybe_unused int seamldr_call(u64 fn, struct tdx_module_args *args)
+static int seamldr_call(u64 fn, struct tdx_module_args *args)
{
guard(raw_spinlock)(&seamldr_lock);
return seamcall_prerr(fn, args);
}
+
+int seamldr_get_info(struct seamldr_info *seamldr_info)
+{
+ /*
+ * Use slow_virt_to_phys() since @seamldr_info may be allocated on
+ * the stack.
+ */
+ struct tdx_module_args args = { .rcx = slow_virt_to_phys(seamldr_info) };
+
+ return seamldr_call(P_SEAMLDR_INFO, &args);
+}
+EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host");
--
2.47.3
^ permalink raw reply related
* [PATCH v6 01/22] x86/virt/tdx: Move low level SEAMCALL helpers out of <asm/tdx.h>
From: Chao Gao @ 2026-03-26 8:43 UTC (permalink / raw)
To: linux-kernel, linux-coco, kvm
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Zhenzhong Duan,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
H. Peter Anvin
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
From: Kai Huang <kai.huang@intel.com>
TDX host core code implements three seamcall*() helpers to make SEAMCALL
to the TDX module. Currently, they are implemented in <asm/tdx.h> and
are exposed to other kernel code which includes <asm/tdx.h>.
However, other than the TDX host core, seamcall*() are not expected to
be used by other kernel code directly. For instance, for all SEAMCALLs
that are used by KVM, the TDX host core exports a wrapper function for
each of them.
Move seamcall*() and related code out of <asm/tdx.h> and make them only
visible to TDX host core.
Since TDX host core tdx.c is already very heavy, don't put low level
seamcall*() code there but to a new dedicated "seamcall_internal.h". Also,
currently tdx.c has seamcall_prerr*() helpers which additionally print
error message when calling seamcall*() fails. Move them to
"seamcall_internal.h" as well. In such way all low level SEAMCALL helpers
are in a dedicated place, which is much more readable.
Copy the copyright notice from the original files and consolidate the
date ranges to:
Copyright (C) 2021-2023 Intel Corporation
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
---
v5:
- s/seamcall.h/seamcall_internal.h [Binbin]
- Fix an unintentional change to sc_retry() during code movement.
v4:
- Collect reviews
- add "internal" to the new header file [Dave]
- document the scope of the new header file [Dave]
- correct the copyright notice [Dave]
v2:
- new
---
arch/x86/include/asm/tdx.h | 47 ----------
arch/x86/virt/vmx/tdx/seamcall_internal.h | 109 ++++++++++++++++++++++
arch/x86/virt/vmx/tdx/tdx.c | 47 +---------
3 files changed, 111 insertions(+), 92 deletions(-)
create mode 100644 arch/x86/virt/vmx/tdx/seamcall_internal.h
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 6b338d7f01b7..cb2219302dfc 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -97,54 +97,7 @@ static inline long tdx_kvm_hypercall(unsigned int nr, unsigned long p1,
#endif /* CONFIG_INTEL_TDX_GUEST && CONFIG_KVM_GUEST */
#ifdef CONFIG_INTEL_TDX_HOST
-u64 __seamcall(u64 fn, struct tdx_module_args *args);
-u64 __seamcall_ret(u64 fn, struct tdx_module_args *args);
-u64 __seamcall_saved_ret(u64 fn, struct tdx_module_args *args);
void tdx_init(void);
-
-#include <linux/preempt.h>
-#include <asm/archrandom.h>
-#include <asm/processor.h>
-
-typedef u64 (*sc_func_t)(u64 fn, struct tdx_module_args *args);
-
-static __always_inline u64 __seamcall_dirty_cache(sc_func_t func, u64 fn,
- struct tdx_module_args *args)
-{
- lockdep_assert_preemption_disabled();
-
- /*
- * SEAMCALLs are made to the TDX module and can generate dirty
- * cachelines of TDX private memory. Mark cache state incoherent
- * so that the cache can be flushed during kexec.
- *
- * This needs to be done before actually making the SEAMCALL,
- * because kexec-ing CPU could send NMI to stop remote CPUs,
- * in which case even disabling IRQ won't help here.
- */
- this_cpu_write(cache_state_incoherent, true);
-
- return func(fn, args);
-}
-
-static __always_inline u64 sc_retry(sc_func_t func, u64 fn,
- struct tdx_module_args *args)
-{
- int retry = RDRAND_RETRY_LOOPS;
- u64 ret;
-
- do {
- preempt_disable();
- ret = __seamcall_dirty_cache(func, fn, args);
- preempt_enable();
- } while (ret == TDX_RND_NO_ENTROPY && --retry);
-
- return ret;
-}
-
-#define seamcall(_fn, _args) sc_retry(__seamcall, (_fn), (_args))
-#define seamcall_ret(_fn, _args) sc_retry(__seamcall_ret, (_fn), (_args))
-#define seamcall_saved_ret(_fn, _args) sc_retry(__seamcall_saved_ret, (_fn), (_args))
int tdx_cpu_enable(void);
int tdx_enable(void);
const char *tdx_dump_mce_info(struct mce *m);
diff --git a/arch/x86/virt/vmx/tdx/seamcall_internal.h b/arch/x86/virt/vmx/tdx/seamcall_internal.h
new file mode 100644
index 000000000000..be5f446467df
--- /dev/null
+++ b/arch/x86/virt/vmx/tdx/seamcall_internal.h
@@ -0,0 +1,109 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * SEAMCALL utilities for TDX host-side operations.
+ *
+ * Provides convenient wrappers around SEAMCALL assembly with retry logic,
+ * error reporting and cache coherency tracking.
+ *
+ * Copyright (C) 2021-2023 Intel Corporation
+ */
+
+#ifndef _X86_VIRT_SEAMCALL_INTERNAL_H
+#define _X86_VIRT_SEAMCALL_INTERNAL_H
+
+#include <linux/printk.h>
+#include <linux/types.h>
+#include <asm/archrandom.h>
+#include <asm/processor.h>
+#include <asm/tdx.h>
+
+u64 __seamcall(u64 fn, struct tdx_module_args *args);
+u64 __seamcall_ret(u64 fn, struct tdx_module_args *args);
+u64 __seamcall_saved_ret(u64 fn, struct tdx_module_args *args);
+
+typedef u64 (*sc_func_t)(u64 fn, struct tdx_module_args *args);
+
+static __always_inline u64 __seamcall_dirty_cache(sc_func_t func, u64 fn,
+ struct tdx_module_args *args)
+{
+ lockdep_assert_preemption_disabled();
+
+ /*
+ * SEAMCALLs are made to the TDX module and can generate dirty
+ * cachelines of TDX private memory. Mark cache state incoherent
+ * so that the cache can be flushed during kexec.
+ *
+ * This needs to be done before actually making the SEAMCALL,
+ * because kexec-ing CPU could send NMI to stop remote CPUs,
+ * in which case even disabling IRQ won't help here.
+ */
+ this_cpu_write(cache_state_incoherent, true);
+
+ return func(fn, args);
+}
+
+static __always_inline u64 sc_retry(sc_func_t func, u64 fn,
+ struct tdx_module_args *args)
+{
+ int retry = RDRAND_RETRY_LOOPS;
+ u64 ret;
+
+ do {
+ preempt_disable();
+ ret = __seamcall_dirty_cache(func, fn, args);
+ preempt_enable();
+ } while (ret == TDX_RND_NO_ENTROPY && --retry);
+
+ return ret;
+}
+
+#define seamcall(_fn, _args) sc_retry(__seamcall, (_fn), (_args))
+#define seamcall_ret(_fn, _args) sc_retry(__seamcall_ret, (_fn), (_args))
+#define seamcall_saved_ret(_fn, _args) sc_retry(__seamcall_saved_ret, (_fn), (_args))
+
+typedef void (*sc_err_func_t)(u64 fn, u64 err, struct tdx_module_args *args);
+
+static inline void seamcall_err(u64 fn, u64 err, struct tdx_module_args *args)
+{
+ pr_err("SEAMCALL (0x%016llx) failed: 0x%016llx\n", fn, err);
+}
+
+static inline void seamcall_err_ret(u64 fn, u64 err,
+ struct tdx_module_args *args)
+{
+ seamcall_err(fn, err, args);
+ pr_err("RCX 0x%016llx RDX 0x%016llx R08 0x%016llx\n",
+ args->rcx, args->rdx, args->r8);
+ pr_err("R09 0x%016llx R10 0x%016llx R11 0x%016llx\n",
+ args->r9, args->r10, args->r11);
+}
+
+static __always_inline int sc_retry_prerr(sc_func_t func,
+ sc_err_func_t err_func,
+ u64 fn, struct tdx_module_args *args)
+{
+ u64 sret = sc_retry(func, fn, args);
+
+ if (sret == TDX_SUCCESS)
+ return 0;
+
+ if (sret == TDX_SEAMCALL_VMFAILINVALID)
+ return -ENODEV;
+
+ if (sret == TDX_SEAMCALL_GP)
+ return -EOPNOTSUPP;
+
+ if (sret == TDX_SEAMCALL_UD)
+ return -EACCES;
+
+ err_func(fn, sret, args);
+ return -EIO;
+}
+
+#define seamcall_prerr(__fn, __args) \
+ sc_retry_prerr(__seamcall, seamcall_err, (__fn), (__args))
+
+#define seamcall_prerr_ret(__fn, __args) \
+ sc_retry_prerr(__seamcall_ret, seamcall_err_ret, (__fn), (__args))
+
+#endif /* _X86_VIRT_SEAMCALL_INTERNAL_H */
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 8b8e165a2001..06d9709ade85 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -39,6 +39,8 @@
#include <asm/cpu_device_id.h>
#include <asm/processor.h>
#include <asm/mce.h>
+
+#include "seamcall_internal.h"
#include "tdx.h"
static u32 tdx_global_keyid __ro_after_init;
@@ -59,51 +61,6 @@ static LIST_HEAD(tdx_memlist);
static struct tdx_sys_info tdx_sysinfo;
-typedef void (*sc_err_func_t)(u64 fn, u64 err, struct tdx_module_args *args);
-
-static inline void seamcall_err(u64 fn, u64 err, struct tdx_module_args *args)
-{
- pr_err("SEAMCALL (0x%016llx) failed: 0x%016llx\n", fn, err);
-}
-
-static inline void seamcall_err_ret(u64 fn, u64 err,
- struct tdx_module_args *args)
-{
- seamcall_err(fn, err, args);
- pr_err("RCX 0x%016llx RDX 0x%016llx R08 0x%016llx\n",
- args->rcx, args->rdx, args->r8);
- pr_err("R09 0x%016llx R10 0x%016llx R11 0x%016llx\n",
- args->r9, args->r10, args->r11);
-}
-
-static __always_inline int sc_retry_prerr(sc_func_t func,
- sc_err_func_t err_func,
- u64 fn, struct tdx_module_args *args)
-{
- u64 sret = sc_retry(func, fn, args);
-
- if (sret == TDX_SUCCESS)
- return 0;
-
- if (sret == TDX_SEAMCALL_VMFAILINVALID)
- return -ENODEV;
-
- if (sret == TDX_SEAMCALL_GP)
- return -EOPNOTSUPP;
-
- if (sret == TDX_SEAMCALL_UD)
- return -EACCES;
-
- err_func(fn, sret, args);
- return -EIO;
-}
-
-#define seamcall_prerr(__fn, __args) \
- sc_retry_prerr(__seamcall, seamcall_err, (__fn), (__args))
-
-#define seamcall_prerr_ret(__fn, __args) \
- sc_retry_prerr(__seamcall_ret, seamcall_err_ret, (__fn), (__args))
-
/*
* Do the module global initialization once and return its result.
* It can be done on any cpu. It's always called with interrupts
--
2.47.3
^ permalink raw reply related
* [PATCH v6 03/22] coco/tdx-host: Expose TDX module version
From: Chao Gao @ 2026-03-26 8:43 UTC (permalink / raw)
To: x86, linux-coco, kvm, linux-kernel
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
For TDX module updates, userspace needs to select compatible update
versions based on the current module version. This design delegates
module selection complexity to userspace because TDX module update
policies are complex and version series are platform-specific.
For example, the 1.5.x series is for certain platform generations, while
the 2.0.x series is intended for others. And TDX module 1.5.x may be
updated to 1.5.y but not to 1.5.y+1.
Expose the TDX module version to userspace via sysfs to aid module
selection. Since the TDX faux device will drive module updates, expose
the version as its attribute.
One bonus of exposing TDX module version via sysfs is: TDX module
version information remains available even after dmesg logs are cleared.
== Background ==
The "faux device + device attribute" approach compares to other update
mechanisms as follows:
1. AMD SEV leverages an existing PCI device for the PSP to expose
metadata. TDX uses a faux device as it doesn't have PCI device
in its architecture.
2. Microcode uses per-CPU virtual devices to report microcode revisions
because CPUs can have different revisions. But, there is only a
single TDX module, so exposing the TDX module version through a global
TDX faux device is appropriate
3. ARM's CCA implementation isn't in-tree yet, but will likely follow a
similar faux device approach, though it's unclear whether they need
to expose firmware version information
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Link: https://lore.kernel.org/all/2025073035-bulginess-rematch-b92e@gregkh/ # [1]
---
v4:
- collect reviews
- Explain other version exposure implementations and why tdx's approach differs
from them
v3:
- Justify the sysfs ABI choice and expand background on other CoCo
implementations.
---
.../ABI/testing/sysfs-devices-faux-tdx-host | 6 ++++
drivers/virt/coco/tdx-host/tdx-host.c | 32 ++++++++++++++++++-
2 files changed, 37 insertions(+), 1 deletion(-)
create mode 100644 Documentation/ABI/testing/sysfs-devices-faux-tdx-host
diff --git a/Documentation/ABI/testing/sysfs-devices-faux-tdx-host b/Documentation/ABI/testing/sysfs-devices-faux-tdx-host
new file mode 100644
index 000000000000..2cf682b65acf
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-faux-tdx-host
@@ -0,0 +1,6 @@
+What: /sys/devices/faux/tdx_host/version
+Contact: linux-coco@lists.linux.dev
+Description: (RO) Report the version of the loaded TDX module. The TDX module
+ version is formatted as x.y.z, where "x" is the major version,
+ "y" is the minor version and "z" is the update version. Versions
+ are used for bug reporting, TDX module updates etc.
diff --git a/drivers/virt/coco/tdx-host/tdx-host.c b/drivers/virt/coco/tdx-host/tdx-host.c
index c77885392b09..f9b1168d0900 100644
--- a/drivers/virt/coco/tdx-host/tdx-host.c
+++ b/drivers/virt/coco/tdx-host/tdx-host.c
@@ -8,6 +8,7 @@
#include <linux/device/faux.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
+#include <linux/sysfs.h>
#include <asm/cpu_device_id.h>
#include <asm/tdx.h>
@@ -18,6 +19,35 @@ static const struct x86_cpu_id tdx_host_ids[] = {
};
MODULE_DEVICE_TABLE(x86cpu, tdx_host_ids);
+/*
+ * TDX module and P-SEAMLDR version convention: "major.minor.update"
+ * (e.g., "1.5.08") with zero-padded two-digit update field.
+ */
+#define TDX_VERSION_FMT "%u.%u.%02u"
+
+static ssize_t version_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ const struct tdx_sys_info *tdx_sysinfo = tdx_get_sysinfo();
+ const struct tdx_sys_info_version *ver;
+
+ if (!tdx_sysinfo)
+ return -ENXIO;
+
+ ver = &tdx_sysinfo->version;
+
+ return sysfs_emit(buf, TDX_VERSION_FMT"\n", ver->major_version,
+ ver->minor_version,
+ ver->update_version);
+}
+static DEVICE_ATTR_RO(version);
+
+static struct attribute *tdx_host_attrs[] = {
+ &dev_attr_version.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(tdx_host);
+
static struct faux_device *fdev;
static int __init tdx_host_init(void)
@@ -25,7 +55,7 @@ static int __init tdx_host_init(void)
if (!x86_match_cpu(tdx_host_ids) || !tdx_get_sysinfo())
return -ENODEV;
- fdev = faux_device_create(KBUILD_MODNAME, NULL, NULL);
+ fdev = faux_device_create_with_groups(KBUILD_MODNAME, NULL, NULL, tdx_host_groups);
if (!fdev)
return -ENODEV;
--
2.47.3
^ permalink raw reply related
* [PATCH v6 04/22] x86/virt/seamldr: Introduce a wrapper for P-SEAMLDR SEAMCALLs
From: Chao Gao @ 2026-03-26 8:43 UTC (permalink / raw)
To: linux-kernel, linux-coco, kvm, linux-rt-devel
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, x86, H. Peter Anvin,
Sebastian Andrzej Siewior, Clark Williams, Steven Rostedt
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
The TDX architecture uses the "SEAMCALL" instruction to communicate with
SEAM mode software. Right now, the only SEAM mode software that the kernel
communicates with is the TDX module. But, there is actually another
component that runs in SEAM mode but it is separate from the TDX module:
the persistent SEAM loader or "P-SEAMLDR". Right now, the only component
that communicates with it is the BIOS which loads the TDX module itself at
boot. But, to support updating the TDX module, the kernel now needs to be
able to talk to it.
P-SEAMLDR SEAMCALLs differ from TDX module SEAMCALLs in areas such as
concurrency requirements. Add a P-SEAMLDR wrapper to handle these
differences and prepare for implementing concrete functions.
Use seamcall_prerr() (not '_ret') because current P-SEAMLDR calls do not
use any output registers other than RAX.
Note that unlike P-SEAMLDR, there is also a non-persistent SEAM loader
("NP-SEAMLDR"). This is an authenticated code module (ACM) that is not
callable at runtime. Only BIOS launches it to load P-SEAMLDR at boot;
the kernel does not need to interact with it for runtime update.
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Link: https://cdrdv2.intel.com/v1/dl/getContent/733582 # [1]
---
v6:
- Don't refer to Intel® Trust Domain CPU Architectural Extensions
[Xiaoyao]
- clarify the usage of seamcall_prerr() [Xiaoyao]
- Improve the explanation for raw_spinlock [Kiryl]
v5:
- Don't save/restore irq flags as P-SEAMLDR calls are made only in process
context
- clarify why raw_spinlock is used [Dave]
v4:
- Give more background about P-SEAMLDR in changelog [Dave]
- Don't handle P-SEAMLDR's "no_entropy" error [Dave]
- Assume current VMCS is preserved across P-SEAMLDR calls [Dave]
- I'm not adding Reviewed-by tags as the code has changed significantly.
v2:
- don't create a new, inferior framework to save/restore VMCS
- use human-friendly language, just "current VMCS" rather than
SDM term "current-VMCS pointer"
- don't mix guard() with goto
---
arch/x86/virt/vmx/tdx/Makefile | 2 +-
arch/x86/virt/vmx/tdx/seamldr.c | 25 +++++++++++++++++++++++++
2 files changed, 26 insertions(+), 1 deletion(-)
create mode 100644 arch/x86/virt/vmx/tdx/seamldr.c
diff --git a/arch/x86/virt/vmx/tdx/Makefile b/arch/x86/virt/vmx/tdx/Makefile
index 90da47eb85ee..d1dbc5cc5697 100644
--- a/arch/x86/virt/vmx/tdx/Makefile
+++ b/arch/x86/virt/vmx/tdx/Makefile
@@ -1,2 +1,2 @@
# SPDX-License-Identifier: GPL-2.0-only
-obj-y += seamcall.o tdx.o
+obj-y += seamcall.o seamldr.o tdx.o
diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
new file mode 100644
index 000000000000..65616dd2f4d2
--- /dev/null
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * P-SEAMLDR support for TDX module management features like runtime updates
+ *
+ * Copyright (C) 2025 Intel Corporation
+ */
+#define pr_fmt(fmt) "seamldr: " fmt
+
+#include <linux/spinlock.h>
+
+#include "seamcall_internal.h"
+
+/*
+ * Serialize P-SEAMLDR calls since the hardware only allows a single CPU to
+ * interact with P-SEAMLDR simultaneously. Use raw version as the calls can
+ * be made with interrupts disabled, where plain spinlocks are prohibited in
+ * PREEMPT_RT kernels as they become sleeping locks.
+ */
+static DEFINE_RAW_SPINLOCK(seamldr_lock);
+
+static __maybe_unused int seamldr_call(u64 fn, struct tdx_module_args *args)
+{
+ guard(raw_spinlock)(&seamldr_lock);
+ return seamcall_prerr(fn, args);
+}
--
2.47.3
^ permalink raw reply related
* [PATCH v6 06/22] coco/tdx-host: Expose P-SEAMLDR information via sysfs
From: Chao Gao @ 2026-03-26 8:43 UTC (permalink / raw)
To: linux-coco, kvm, linux-kernel
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, x86, H. Peter Anvin
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
TDX module updates require userspace to select the appropriate module
to load. Expose necessary information to facilitate this decision. Two
values are needed:
- P-SEAMLDR version: for compatibility checks between TDX module and
P-SEAMLDR
- num_remaining_updates: indicates how many updates can be performed
Expose them as tdx-host device attributes. Make seamldr attributes
visible only when the update feature is supported, as that's their sole
purpose. Unconditional exposure is also problematic because reading them
triggers P-SEAMLDR calls that break KVM on CPUs with a specific erratum
(to be enumerated and handled in a later patch).
Signed-off-by: Chao Gao <chao.gao@intel.com>
---
v6:
- use TDX_VERSION_FMT macro [Dave]
- drop revision/chapter numbers [Kiryl/Xiaoyao]
- use is_visible to control seamldr attribute visibility
rather than do that manually during device probe. Due
to this change, drop all RBs.
v5:
- fix typos [Binbin]
- register seamldr_group during device probe
v4:
- Make seamldr attribute permission "0400" [Dave]
- Don't include implementation details in OS ABI docs [Dave]
- Tag tdx_host_group as static [Kai]
v3:
- use #ifdef rather than .is_visible() to control P-SEAMLDR sysfs
visibility [Yilun]
---
.../ABI/testing/sysfs-devices-faux-tdx-host | 22 ++++++
arch/x86/include/asm/tdx.h | 6 ++
drivers/virt/coco/tdx-host/tdx-host.c | 76 ++++++++++++++++++-
3 files changed, 103 insertions(+), 1 deletion(-)
diff --git a/Documentation/ABI/testing/sysfs-devices-faux-tdx-host b/Documentation/ABI/testing/sysfs-devices-faux-tdx-host
index 2cf682b65acf..f7221f2e5fec 100644
--- a/Documentation/ABI/testing/sysfs-devices-faux-tdx-host
+++ b/Documentation/ABI/testing/sysfs-devices-faux-tdx-host
@@ -4,3 +4,25 @@ Description: (RO) Report the version of the loaded TDX module. The TDX module
version is formatted as x.y.z, where "x" is the major version,
"y" is the minor version and "z" is the update version. Versions
are used for bug reporting, TDX module updates etc.
+
+What: /sys/devices/faux/tdx_host/seamldr/version
+Contact: linux-coco@lists.linux.dev
+Description: (RO) Report the version of the loaded SEAM loader. The SEAM
+ loader version is formatted as x.y.z, where "x" is the major
+ version, "y" is the minor version and "z" is the update version.
+ Versions are used for bug reporting and compatibility checks.
+
+What: /sys/devices/faux/tdx_host/seamldr/num_remaining_updates
+Contact: linux-coco@lists.linux.dev
+Description: (RO) Report the number of remaining updates. TDX maintains a
+ log about each TDX module that has been loaded. This log has
+ a finite size, which limits the number of TDX module updates
+ that can be performed.
+
+ After each successful update, the number reduces by one. Once it
+ reaches zero, further updates will fail until next reboot. The
+ number is always zero if the P-SEAMLDR doesn't support updates.
+
+ See Intel® Trust Domain Extensions - SEAM Loader (SEAMLDR)
+ Interface Specification, Chapter "SEAMLDR_INFO" and Chapter
+ "SEAMLDR.INSTALL" for more information.
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index cb2219302dfc..1fb2a3f6b9e1 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -103,6 +103,12 @@ int tdx_enable(void);
const char *tdx_dump_mce_info(struct mce *m);
const struct tdx_sys_info *tdx_get_sysinfo(void);
+static inline bool tdx_supports_runtime_update(const struct tdx_sys_info *sysinfo)
+{
+ /* To be enabled when kernel is ready. */
+ return false;
+}
+
int tdx_guest_keyid_alloc(void);
u32 tdx_get_nr_guest_keyids(void);
void tdx_guest_keyid_free(unsigned int keyid);
diff --git a/drivers/virt/coco/tdx-host/tdx-host.c b/drivers/virt/coco/tdx-host/tdx-host.c
index f9b1168d0900..01f68c390a49 100644
--- a/drivers/virt/coco/tdx-host/tdx-host.c
+++ b/drivers/virt/coco/tdx-host/tdx-host.c
@@ -11,6 +11,7 @@
#include <linux/sysfs.h>
#include <asm/cpu_device_id.h>
+#include <asm/seamldr.h>
#include <asm/tdx.h>
static const struct x86_cpu_id tdx_host_ids[] = {
@@ -46,7 +47,80 @@ static struct attribute *tdx_host_attrs[] = {
&dev_attr_version.attr,
NULL,
};
-ATTRIBUTE_GROUPS(tdx_host);
+
+static const struct attribute_group tdx_host_group = {
+ .attrs = tdx_host_attrs,
+};
+
+static ssize_t seamldr_version_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct seamldr_info info;
+ int ret;
+
+ ret = seamldr_get_info(&info);
+ if (ret)
+ return ret;
+
+ return sysfs_emit(buf, TDX_VERSION_FMT"\n", info.major_version,
+ info.minor_version,
+ info.update_version);
+}
+
+static ssize_t num_remaining_updates_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct seamldr_info info;
+ int ret;
+
+ ret = seamldr_get_info(&info);
+ if (ret)
+ return ret;
+
+ return sysfs_emit(buf, "%u\n", info.num_remaining_updates);
+}
+
+/*
+ * Open-code DEVICE_ATTR_ADMIN_RO to specify a different 'show' function
+ * for P-SEAMLDR version as version_show() is used for TDX module version.
+ *
+ * Admin-only readable as reading these attributes calls into P-SEAMLDR,
+ * which may have potential performance and system impact.
+ */
+static struct device_attribute dev_attr_seamldr_version =
+ __ATTR(version, 0400, seamldr_version_show, NULL);
+static DEVICE_ATTR_ADMIN_RO(num_remaining_updates);
+
+static struct attribute *seamldr_attrs[] = {
+ &dev_attr_seamldr_version.attr,
+ &dev_attr_num_remaining_updates.attr,
+ NULL,
+};
+
+static bool seamldr_group_visible(struct kobject *kobj)
+{
+ const struct tdx_sys_info *sysinfo = tdx_get_sysinfo();
+
+ if (!sysinfo)
+ return false;
+
+ return tdx_supports_runtime_update(sysinfo);
+}
+
+DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE(seamldr);
+
+static const struct attribute_group seamldr_group = {
+ .name = "seamldr",
+ .attrs = seamldr_attrs,
+ .is_visible = SYSFS_GROUP_VISIBLE(seamldr),
+};
+
+static const struct attribute_group *tdx_host_groups[] = {
+ &tdx_host_group,
+ &seamldr_group,
+ NULL,
+};
static struct faux_device *fdev;
--
2.47.3
^ permalink raw reply related
* [PATCH v6 07/22] coco/tdx-host: Implement firmware upload sysfs ABI for TDX module updates
From: Chao Gao @ 2026-03-26 8:43 UTC (permalink / raw)
To: linux-kernel, linux-coco, kvm
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, x86, H. Peter Anvin
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
Linux kernel supports two primary firmware update mechanisms:
- request_firmware()
- firmware upload (or fw_upload)
The former is used by microcode updates, SEV firmware updates, etc. The
latter is used by CXL and FPGA firmware updates.
One key difference between them is: request_firmware() loads a named
file from the filesystem where the filename is kernel-controlled, while
fw_upload accepts firmware data directly from userspace.
Use fw_upload for TDX module updates as loading a named file isn't
suitable for TDX (see below for more reasons). Specifically, register
TDX faux device with fw_upload framework to expose sysfs interfaces
and implement operations to process data blobs supplied by userspace.
Implementation notes:
1. P-SEAMLDR processes the entire update at once rather than
chunk-by-chunk, so .write() is called only once per update; so the
offset should be always 0.
2. An update completes synchronously within .write(), meaning
.poll_complete() is only called after the update succeeds and so always
returns success
Why fw_upload instead of request_firmware()?
============================================
The explicit file selection capabilities of fw_upload is preferred over
the implicit file selection of request_firmware() for the following
reasons:
a. Intel distributes all versions of the TDX module, allowing admins to
load any version rather than always defaulting to the latest. This
flexibility is necessary because future extensions may require reverting to
a previous version to clear fatal errors.
b. Some module version series are platform-specific. For example, the 1.5.x
series is for certain platform generations, while the 2.0.x series is
intended for others.
c. The update policy for TDX module updates is non-linear at times. The
latest TDX module may not be compatible. For example, TDX module 1.5.x
may be updated to 1.5.y but not to 1.5.y+1. This policy is documented
separately in a file released along with each TDX module release.
So, the default policy of "request_firmware()" of "always load latest", is
not suitable for TDX. Userspace needs to deploy a more sophisticated policy
check (e.g., latest may not be compatible), and there is potential
operator choice to consider.
Just have userspace pick rather than add kernel mechanism to change the
default policy of request_firmware().
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
---
v6:
- Remove unused "-ENOSPC" error mapping—this series never returns it
v5:
- remove a tail comment [Yan]
- remove is_vmalloc_addr() check [Dave]
- use devm_add_action_or_reset() for deinit [Yilun]
- remove global tdx_fwl [Yilun]
- clarify request_firmware() doesn't take filename from userspace
[Rick]
v4:
- make tdx_fwl static [Kai]
- don't support update canceling [Yilun]
- explain why seamldr_init() doesn't return an error [Kai]
- bail out if TDX module updates are not supported [Kai]
- name the firmware "tdx_module" instead of "seamldr_upload" [Cedric]
v3:
- clear "cancel_request" in the "prepare" phase [Binbin]
- Don't fail the whole tdx-host device if seamldr_init() met an error
[Yilun]
- Add kdoc for seamldr_install_module() and verify that the input
buffer is vmalloc'd. [Yilun]
---
arch/x86/include/asm/seamldr.h | 1 +
arch/x86/virt/vmx/tdx/seamldr.c | 15 ++++
drivers/virt/coco/tdx-host/Kconfig | 2 +
drivers/virt/coco/tdx-host/tdx-host.c | 99 ++++++++++++++++++++++++++-
4 files changed, 115 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/seamldr.h b/arch/x86/include/asm/seamldr.h
index c67e5bc910a9..ac6f80f7208b 100644
--- a/arch/x86/include/asm/seamldr.h
+++ b/arch/x86/include/asm/seamldr.h
@@ -32,5 +32,6 @@ struct seamldr_info {
static_assert(sizeof(struct seamldr_info) == 256);
int seamldr_get_info(struct seamldr_info *seamldr_info);
+int seamldr_install_module(const u8 *data, u32 size);
#endif /* _ASM_X86_SEAMLDR_H */
diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index 8410df3a0bf4..e93a5d90a3ee 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -6,6 +6,7 @@
*/
#define pr_fmt(fmt) "seamldr: " fmt
+#include <linux/mm.h>
#include <linux/spinlock.h>
#include <asm/seamldr.h>
@@ -40,3 +41,17 @@ int seamldr_get_info(struct seamldr_info *seamldr_info)
return seamldr_call(P_SEAMLDR_INFO, &args);
}
EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host");
+
+/**
+ * seamldr_install_module - Install a new TDX module.
+ * @data: Pointer to the TDX module update blob.
+ * @size: Size of the TDX module update blob.
+ *
+ * Returns 0 on success, negative error code on failure.
+ */
+int seamldr_install_module(const u8 *data, u32 size)
+{
+ /* TODO: Update TDX module here */
+ return 0;
+}
+EXPORT_SYMBOL_FOR_MODULES(seamldr_install_module, "tdx-host");
diff --git a/drivers/virt/coco/tdx-host/Kconfig b/drivers/virt/coco/tdx-host/Kconfig
index d35d85ef91c0..ca600a39d97b 100644
--- a/drivers/virt/coco/tdx-host/Kconfig
+++ b/drivers/virt/coco/tdx-host/Kconfig
@@ -1,6 +1,8 @@
config TDX_HOST_SERVICES
tristate "TDX Host Services Driver"
depends on INTEL_TDX_HOST
+ select FW_LOADER
+ select FW_UPLOAD
default m
help
Enable access to TDX host services like module update and
diff --git a/drivers/virt/coco/tdx-host/tdx-host.c b/drivers/virt/coco/tdx-host/tdx-host.c
index 01f68c390a49..d4a552853021 100644
--- a/drivers/virt/coco/tdx-host/tdx-host.c
+++ b/drivers/virt/coco/tdx-host/tdx-host.c
@@ -6,6 +6,7 @@
*/
#include <linux/device/faux.h>
+#include <linux/firmware.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/sysfs.h>
@@ -98,7 +99,7 @@ static struct attribute *seamldr_attrs[] = {
NULL,
};
-static bool seamldr_group_visible(struct kobject *kobj)
+static bool can_expose_seamldr(void)
{
const struct tdx_sys_info *sysinfo = tdx_get_sysinfo();
@@ -108,6 +109,11 @@ static bool seamldr_group_visible(struct kobject *kobj)
return tdx_supports_runtime_update(sysinfo);
}
+static bool seamldr_group_visible(struct kobject *kobj)
+{
+ return can_expose_seamldr();
+}
+
DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE(seamldr);
static const struct attribute_group seamldr_group = {
@@ -122,6 +128,95 @@ static const struct attribute_group *tdx_host_groups[] = {
NULL,
};
+static enum fw_upload_err tdx_fw_prepare(struct fw_upload *fwl,
+ const u8 *data, u32 size)
+{
+ return FW_UPLOAD_ERR_NONE;
+}
+
+static enum fw_upload_err tdx_fw_write(struct fw_upload *fwl, const u8 *data,
+ u32 offset, u32 size, u32 *written)
+{
+ int ret;
+
+ /*
+ * tdx_fw_write() always processes all data on the first call with
+ * offset == 0. Since it never returns partial success (it either
+ * succeeds completely or fails), there is no subsequent call with
+ * non-zero offsets.
+ */
+ WARN_ON_ONCE(offset);
+ ret = seamldr_install_module(data, size);
+ switch (ret) {
+ case 0:
+ *written = size;
+ return FW_UPLOAD_ERR_NONE;
+ case -EBUSY:
+ return FW_UPLOAD_ERR_BUSY;
+ case -EIO:
+ return FW_UPLOAD_ERR_HW_ERROR;
+ case -ENOMEM:
+ return FW_UPLOAD_ERR_RW_ERROR;
+ default:
+ return FW_UPLOAD_ERR_FW_INVALID;
+ }
+}
+
+static enum fw_upload_err tdx_fw_poll_complete(struct fw_upload *fwl)
+{
+ /*
+ * TDX module updates are completed in the previous phase
+ * (tdx_fw_write()). If any error occurred, the previous phase
+ * would return an error code to abort the update process. In
+ * other words, reaching this point means the update succeeded.
+ */
+ return FW_UPLOAD_ERR_NONE;
+}
+
+/*
+ * TDX module updates cannot be cancelled. Provide a stub function since
+ * the firmware upload framework requires a .cancel operation.
+ */
+static void tdx_fw_cancel(struct fw_upload *fwl)
+{
+}
+
+static const struct fw_upload_ops tdx_fw_ops = {
+ .prepare = tdx_fw_prepare,
+ .write = tdx_fw_write,
+ .poll_complete = tdx_fw_poll_complete,
+ .cancel = tdx_fw_cancel,
+};
+
+static void seamldr_deinit(void *tdx_fwl)
+{
+ firmware_upload_unregister(tdx_fwl);
+}
+
+static int seamldr_init(struct device *dev)
+{
+ struct fw_upload *tdx_fwl;
+
+ if (!can_expose_seamldr())
+ return 0;
+
+ tdx_fwl = firmware_upload_register(THIS_MODULE, dev, "tdx_module",
+ &tdx_fw_ops, NULL);
+ if (IS_ERR(tdx_fwl))
+ return PTR_ERR(tdx_fwl);
+
+ return devm_add_action_or_reset(dev, seamldr_deinit, tdx_fwl);
+}
+
+static int tdx_host_probe(struct faux_device *fdev)
+{
+ return seamldr_init(&fdev->dev);
+}
+
+static const struct faux_device_ops tdx_host_ops = {
+ .probe = tdx_host_probe,
+};
+
static struct faux_device *fdev;
static int __init tdx_host_init(void)
@@ -129,7 +224,7 @@ static int __init tdx_host_init(void)
if (!x86_match_cpu(tdx_host_ids) || !tdx_get_sysinfo())
return -ENODEV;
- fdev = faux_device_create_with_groups(KBUILD_MODNAME, NULL, NULL, tdx_host_groups);
+ fdev = faux_device_create_with_groups(KBUILD_MODNAME, NULL, &tdx_host_ops, tdx_host_groups);
if (!fdev)
return -ENODEV;
--
2.47.3
^ permalink raw reply related
* [PATCH v6 09/22] x86/virt/seamldr: Introduce skeleton for TDX module updates
From: Chao Gao @ 2026-03-26 8:44 UTC (permalink / raw)
To: linux-kernel, linux-coco, kvm
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, x86, H. Peter Anvin
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
TDX module updates require careful synchronization with other TDX
operations. The requirements are (#1/#2 reflect current behavior that
must be preserved):
1. SEAMCALLs need to be callable from both process and IRQ contexts.
2. SEAMCALLs need to be able to run concurrently across CPUs
3. During updates, only update-related SEAMCALLs are permitted; all
other SEAMCALLs shouldn't be called.
4. During updates, all online CPUs must participate in the update work.
No single lock primitive satisfies all requirements. For instance,
rwlock_t handles #1/#2 but fails #4: CPUs spinning with IRQs disabled
cannot be directed to perform update work.
Use stop_machine() as it is the only well-understood mechanism that can
meet all requirements.
And TDX module updates consist of several steps (See Intel® Trust Domain
Extensions (Intel® TDX) Module Base Architecture Specification, Chapter
"TD-Preserving TDX module Update"). Ordering requirements between steps
mandate lockstep synchronization across all CPUs.
multi_cpu_stop() is a good example of performing a multi-step task in
lockstep. But it doesn't synchronize steps within the callback function
it takes. So, implement one based on its pattern to establish the
skeleton for TDX module updates. Specifically, add a global state
machine where each state represents a step in the update flow. The state
advances only after all CPUs acknowledge completing their work in the
current state. This acknowledgment mechanism is what ensures lockstep
execution.
Potential alternative to stop_machine()
=======================================
An alternative approach is to lock all KVM entry points and kick all
vCPUs. Here, KVM entry points refer to KVM VM/vCPU ioctl entry points,
implemented in KVM common code (virt/kvm). Adding a locking mechanism
there would affect all architectures KVM supports. And to lock only TDX
vCPUs, new logic would be needed to identify TDX vCPUs, which the KVM
common code currently lacks. This would add significant complexity and
maintenance overhead to KVM for this TDX-specific use case.
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
---
v5:
- rewrite the commit message [Rick]
- use a lock to synchronize accesses to update_data [Dave]
- rename tdp_state and tdp_data to module_update_state and update_data
for clarity [Kai]
v2:
- refine the changlog to follow context-problem-solution structure
- move alternative discussions at the end of the changelog
- add a comment about state machine transition
- Move rcu_momentary_eqs() call to the else branch.
---
arch/x86/virt/vmx/tdx/seamldr.c | 77 ++++++++++++++++++++++++++++++++-
1 file changed, 75 insertions(+), 2 deletions(-)
diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index a0bd02a59086..ed6a092b11e2 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -7,8 +7,10 @@
#define pr_fmt(fmt) "seamldr: " fmt
#include <linux/mm.h>
+#include <linux/nmi.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
+#include <linux/stop_machine.h>
#include <asm/seamldr.h>
@@ -180,6 +182,77 @@ static struct seamldr_params *init_seamldr_params(const u8 *data, u32 size)
return alloc_seamldr_params(module, module_size, sig, sig_size);
}
+/*
+ * During a TDX module update, all CPUs start from MODULE_UPDATE_START and
+ * progress to MODULE_UPDATE_DONE. Each state is associated with certain
+ * work. For some states, just one CPU needs to perform the work, while
+ * other CPUs just wait during those states.
+ */
+enum module_update_state {
+ MODULE_UPDATE_START,
+ MODULE_UPDATE_DONE,
+};
+
+static struct {
+ enum module_update_state state;
+ int thread_ack;
+ /*
+ * Protect update_data. Raw spinlock as it will be acquired from
+ * interrupt-disabled contexts.
+ */
+ raw_spinlock_t lock;
+} update_data = {
+ .lock = __RAW_SPIN_LOCK_UNLOCKED(update_data.lock)
+};
+
+static void set_target_state(enum module_update_state state)
+{
+ /* Reset ack counter. */
+ update_data.thread_ack = num_online_cpus();
+ update_data.state = state;
+}
+
+/* Last one to ack a state moves to the next state. */
+static void ack_state(void)
+{
+ guard(raw_spinlock)(&update_data.lock);
+ update_data.thread_ack--;
+ if (!update_data.thread_ack)
+ set_target_state(update_data.state + 1);
+}
+
+/*
+ * See multi_cpu_stop() from where this multi-cpu state-machine was
+ * adopted, and the rationale for touch_nmi_watchdog().
+ */
+static int do_seamldr_install_module(void *seamldr_params)
+{
+ enum module_update_state newstate, curstate = MODULE_UPDATE_START;
+ int ret = 0;
+
+ do {
+ /* Chill out and re-read update_data. */
+ cpu_relax();
+ newstate = READ_ONCE(update_data.state);
+
+ if (newstate != curstate) {
+ curstate = newstate;
+ switch (curstate) {
+ /* TODO: add the update steps. */
+ default:
+ break;
+ }
+
+ ack_state();
+ } else {
+ touch_nmi_watchdog();
+ rcu_momentary_eqs();
+ }
+ } while (curstate != MODULE_UPDATE_DONE);
+
+ return ret;
+}
+
DEFINE_FREE(free_seamldr_params, struct seamldr_params *,
if (!IS_ERR_OR_NULL(_T)) free_seamldr_params(_T))
@@ -197,7 +270,7 @@ int seamldr_install_module(const u8 *data, u32 size)
if (IS_ERR(params))
return PTR_ERR(params);
- /* TODO: Update TDX module here */
- return 0;
+ set_target_state(MODULE_UPDATE_START + 1);
+ return stop_machine(do_seamldr_install_module, params, cpu_online_mask);
}
EXPORT_SYMBOL_FOR_MODULES(seamldr_install_module, "tdx-host");
--
2.47.3
^ permalink raw reply related
* [PATCH v6 08/22] x86/virt/seamldr: Allocate and populate a module update request
From: Chao Gao @ 2026-03-26 8:43 UTC (permalink / raw)
To: linux-kernel, linux-coco, kvm
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, x86, H. Peter Anvin
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
P-SEAMLDR uses the SEAMLDR_PARAMS structure to describe TDX module
update requests. This structure contains physical addresses pointing to
the module binary and its signature file (or sigstruct), along with an
update scenario field.
TDX modules are distributed in the tdx_blob format defined in
blob_structure.txt from the "Intel TDX module Binaries Repository". A
tdx_blob contains a header, sigstruct, and module binary. This is also the
format supplied by the userspace to the kernel.
Parse the tdx_blob format and populate a SEAMLDR_PARAMS structure
accordingly. This structure will be passed to P-SEAMLDR to initiate the
update.
Note that the sigstruct_pa field in SEAMLDR_PARAMS has been extended to
a 4-element array. The updated "SEAM Loader (SEAMLDR) Interface
Specification" will be published separately. P-SEAMLDR compatibility
validation (such as 4KB vs 16KB sigstruct support) is left to userspace,
which must verify the P-SEAMLDR version meets the TDX module's minimum
requirements.
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
---
v6:
- clarify tdx_blob's @offset_of_module and @len fields [Kiryl]
- clarify comment to explicitly call out the PAGE_SIZE != SZ_4K case
[Kiryl]
v5:
- use a macro for tdx_blob version (0x100) [Yan]
- don't do alignment checking for the binary/sigstruct [Rick]
- drop blob's sigstruct and validation checking
- set seamldr_params.version to 1 when necessary
- drop the link to blob_structure.txt which might be unstable [Kai]
v4:
- Remove checksum verification as it is optional
- Convert comments to is_vmalloc_addr() checks [Kai]
- Explain size/alignment checks in alloc_seamldr_params() [Kai]
v3:
- Print tdx_blob version in hex [Binbin]
- Drop redundant sigstruct alignment check [Yilun]
- Note buffers passed from firmware upload infrastructure are
vmalloc()'d above alloc_seamldr_params()
---
arch/x86/virt/vmx/tdx/seamldr.c | 146 ++++++++++++++++++++++++++++++++
1 file changed, 146 insertions(+)
diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index e93a5d90a3ee..a0bd02a59086 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -7,6 +7,7 @@
#define pr_fmt(fmt) "seamldr: " fmt
#include <linux/mm.h>
+#include <linux/slab.h>
#include <linux/spinlock.h>
#include <asm/seamldr.h>
@@ -16,6 +17,33 @@
/* P-SEAMLDR SEAMCALL leaf function */
#define P_SEAMLDR_INFO 0x8000000000000000
+#define SEAMLDR_MAX_NR_MODULE_4KB_PAGES 496
+#define SEAMLDR_MAX_NR_SIG_4KB_PAGES 4
+
+/*
+ * The seamldr_params "scenario" field specifies the operation mode:
+ * 0: Install TDX module from scratch (not used by kernel)
+ * 1: Update existing TDX module to a compatible version
+ */
+#define SEAMLDR_SCENARIO_UPDATE 1
+
+/*
+ * This is called the "SEAMLDR_PARAMS" data structure and is defined
+ * in "SEAM Loader (SEAMLDR) Interface Specification".
+ *
+ * It describes the TDX module that will be installed.
+ */
+struct seamldr_params {
+ u32 version;
+ u32 scenario;
+ u64 sigstruct_pa[SEAMLDR_MAX_NR_SIG_4KB_PAGES];
+ u8 reserved[80];
+ u64 num_module_pages;
+ u64 mod_pages_pa_list[SEAMLDR_MAX_NR_MODULE_4KB_PAGES];
+} __packed;
+
+static_assert(sizeof(struct seamldr_params) == 4096);
+
/*
* Serialize P-SEAMLDR calls since the hardware only allows a single CPU to
* interact with P-SEAMLDR simultaneously. Use raw version as the calls can
@@ -42,6 +70,119 @@ int seamldr_get_info(struct seamldr_info *seamldr_info)
}
EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host");
+static void free_seamldr_params(struct seamldr_params *params)
+{
+ free_page((unsigned long)params);
+}
+
+static struct seamldr_params *alloc_seamldr_params(const void *module, unsigned int module_size,
+ const void *sig, unsigned int sig_size)
+{
+ struct seamldr_params *params;
+ const u8 *ptr;
+ int i;
+
+ if (module_size > SEAMLDR_MAX_NR_MODULE_4KB_PAGES * SZ_4K)
+ return ERR_PTR(-EINVAL);
+
+ if (sig_size > SEAMLDR_MAX_NR_SIG_4KB_PAGES * SZ_4K)
+ return ERR_PTR(-EINVAL);
+
+ params = (struct seamldr_params *)get_zeroed_page(GFP_KERNEL);
+ if (!params)
+ return ERR_PTR(-ENOMEM);
+
+ /*
+ * Only use version 1 when required (sigstruct > 4KB) for backward
+ * compatibility with P-SEAMLDR that lacks version 1 support.
+ */
+ if (sig_size > SZ_4K)
+ params->version = 1;
+ else
+ params->version = 0;
+
+ params->scenario = SEAMLDR_SCENARIO_UPDATE;
+
+ ptr = sig;
+ for (i = 0; i < sig_size / SZ_4K; i++) {
+ /*
+ * @sig is 4KB-aligned, but that does not imply PAGE_SIZE
+ * alignment when PAGE_SIZE != SZ_4K. Always include the
+ * in-page offset.
+ */
+ params->sigstruct_pa[i] = (vmalloc_to_pfn(ptr) << PAGE_SHIFT) +
+ ((unsigned long)ptr & ~PAGE_MASK);
+ ptr += SZ_4K;
+ }
+
+ params->num_module_pages = module_size / SZ_4K;
+
+ ptr = module;
+ for (i = 0; i < params->num_module_pages; i++) {
+ params->mod_pages_pa_list[i] = (vmalloc_to_pfn(ptr) << PAGE_SHIFT) +
+ ((unsigned long)ptr & ~PAGE_MASK);
+ ptr += SZ_4K;
+ }
+
+ return params;
+}
+
+/*
+ * Intel TDX module blob. Its format is defined at:
+ * https://github.com/intel/tdx-module-binaries/blob/main/blob_structure.txt
+ *
+ * Note this structure differs from the reference above: the two variable-length
+ * fields "@sigstruct" and "@module" are represented as a single "@data" field
+ * here and split programmatically using the offset_of_module value.
+ *
+ * Note @offset_of_module is relative to the start of struct tdx_blob, not
+ * @data, and @length is the total length of the blob, not the length of
+ * @data.
+ */
+struct tdx_blob {
+ u16 version;
+ u16 checksum;
+ u32 offset_of_module;
+ u8 signature[8];
+ u32 length;
+ u32 reserved0;
+ u64 reserved1[509];
+ u8 data[];
+} __packed;
+
+/* Supported versions of the tdx_blob */
+#define TDX_BLOB_VERSION_1 0x100
+
+static struct seamldr_params *init_seamldr_params(const u8 *data, u32 size)
+{
+ const struct tdx_blob *blob = (const void *)data;
+ int module_size, sig_size;
+ const void *sig, *module;
+
+ /* Ensure the size is valid otherwise reading any field from the blob may overflow. */
+ if (size <= sizeof(struct tdx_blob) || size <= blob->offset_of_module)
+ return ERR_PTR(-EINVAL);
+
+ if (blob->version != TDX_BLOB_VERSION_1) {
+ pr_err("unsupported blob version: %x\n", blob->version);
+ return ERR_PTR(-EINVAL);
+ }
+
+ /* Split the blob into a sigstruct and a module. */
+ sig = blob->data;
+ sig_size = blob->offset_of_module - sizeof(struct tdx_blob);
+ module = data + blob->offset_of_module;
+ module_size = size - blob->offset_of_module;
+
+ if (sig_size <= 0 || module_size <= 0 || blob->length != size)
+ return ERR_PTR(-EINVAL);
+
+ return alloc_seamldr_params(module, module_size, sig, sig_size);
+}
+
+DEFINE_FREE(free_seamldr_params, struct seamldr_params *,
+ if (!IS_ERR_OR_NULL(_T)) free_seamldr_params(_T))
+
/**
* seamldr_install_module - Install a new TDX module.
* @data: Pointer to the TDX module update blob.
@@ -51,6 +192,11 @@ EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host");
*/
int seamldr_install_module(const u8 *data, u32 size)
{
+ struct seamldr_params *params __free(free_seamldr_params) =
+ init_seamldr_params(data, size);
+ if (IS_ERR(params))
+ return PTR_ERR(params);
+
/* TODO: Update TDX module here */
return 0;
}
--
2.47.3
^ permalink raw reply related
* [PATCH v6 10/22] x86/virt/seamldr: Abort updates if errors occurred midway
From: Chao Gao @ 2026-03-26 8:44 UTC (permalink / raw)
To: linux-kernel, linux-coco, kvm
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, x86, H. Peter Anvin
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
The TDX module update process has multiple steps, each of which may
encounter failures.
The current state machine of updates proceeds to the next step regardless
of errors. But continuing updates when errors occur midway is pointless.
Abort the update by setting a flag to indicate that a CPU has encountered
an error, forcing all CPUs to exit the execution loop. Note that failing
CPUs do not acknowledge the current step. This keeps all other CPUs waiting
in the current step (since advancing to the next step requires all CPUs to
acknowledge the current step) until they detect the fault flag and exit the
loop.
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
---
v6:
- change failure indicator from int to boolean [Kiryl]
- replace lock with WRITE_ONCE for @failed [Kiryl]
v5:
- Replace failed count from atomic_t to int since it's now protected by
a lock.
v3:
- Instead of fast-forward to the final stage, exit the execution loop
directly.
---
arch/x86/virt/vmx/tdx/seamldr.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index ed6a092b11e2..771671b7755b 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -196,6 +196,7 @@ enum module_update_state {
static struct {
enum module_update_state state;
int thread_ack;
+ bool failed;
/*
* Protect update_data. Raw spinlock as it will be acquired from
* interrupt-disabled contexts.
@@ -243,12 +244,15 @@ static int do_seamldr_install_module(void *seamldr_params)
break;
}
- ack_state();
+ if (ret)
+ WRITE_ONCE(update_data.failed, true);
+ else
+ ack_state();
} else {
touch_nmi_watchdog();
rcu_momentary_eqs();
}
- } while (curstate != MODULE_UPDATE_DONE);
+ } while (curstate != MODULE_UPDATE_DONE && !READ_ONCE(update_data.failed));
return ret;
}
@@ -270,6 +274,7 @@ int seamldr_install_module(const u8 *data, u32 size)
if (IS_ERR(params))
return PTR_ERR(params);
+ update_data.failed = false;
set_target_state(MODULE_UPDATE_START + 1);
return stop_machine(do_seamldr_install_module, params, cpu_online_mask);
}
--
2.47.3
^ permalink raw reply related
* [PATCH v6 13/22] x86/virt/seamldr: Install a new TDX module
From: Chao Gao @ 2026-03-26 8:44 UTC (permalink / raw)
To: linux-kernel, linux-coco, kvm
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, x86, H. Peter Anvin
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
Following the shutdown of the existing TDX module, the update process
continues with installing the new module. P-SEAMLDR provides the
SEAMLDR.INSTALL SEAMCALL to perform this installation, which must be
executed on all CPUs.
Implement SEAMLDR.INSTALL and execute it on every CPU.
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
---
v6:
- wrap seamldr_call(P_SEAMLDR_INSTALL..) in a helper [Kiryl]
v5:
- drop "serially" from the changelog as it doesn't matter to
this patch
---
arch/x86/virt/vmx/tdx/seamldr.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index a8fd29818378..0c282a7565a1 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -19,6 +19,7 @@
/* P-SEAMLDR SEAMCALL leaf function */
#define P_SEAMLDR_INFO 0x8000000000000000
+#define P_SEAMLDR_INSTALL 0x8000000000000001
#define SEAMLDR_MAX_NR_MODULE_4KB_PAGES 496
#define SEAMLDR_MAX_NR_SIG_4KB_PAGES 4
@@ -73,6 +74,13 @@ int seamldr_get_info(struct seamldr_info *seamldr_info)
}
EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host");
+static int seamldr_install(const struct seamldr_params *params)
+{
+ struct tdx_module_args args = { .rcx = __pa(params) };
+
+ return seamldr_call(P_SEAMLDR_INSTALL, &args);
+}
+
static void free_seamldr_params(struct seamldr_params *params)
{
free_page((unsigned long)params);
@@ -192,6 +200,7 @@ static struct seamldr_params *init_seamldr_params(const u8 *data, u32 size)
enum module_update_state {
MODULE_UPDATE_START,
MODULE_UPDATE_SHUTDOWN,
+ MODULE_UPDATE_CPU_INSTALL,
MODULE_UPDATE_DONE,
};
@@ -249,6 +258,9 @@ static int do_seamldr_install_module(void *seamldr_params)
if (primary)
ret = tdx_module_shutdown();
break;
+ case MODULE_UPDATE_CPU_INSTALL:
+ ret = seamldr_install(seamldr_params);
+ break;
default:
break;
}
--
2.47.3
^ permalink raw reply related
* [PATCH v6 11/22] x86/virt/seamldr: Shut down the current TDX module
From: Chao Gao @ 2026-03-26 8:44 UTC (permalink / raw)
To: linux-kernel, linux-coco, kvm
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, x86, H. Peter Anvin
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
The first step of TDX module updates is shutting down the current TDX
Module. This step also packs state information that needs to be
preserved across updates as handoff data, which will be consumed by the
updated module. The handoff data is stored internally in the SEAM range
and is hidden from the kernel.
To ensure a successful update, the new module must be able to consume
the handoff data generated by the old module. Since handoff data layout
may change between modules, the handoff data is versioned. Each module
has a native handoff version and provides backward support for several
older versions.
The complete handoff versioning protocol is complex as it supports both
module upgrades and downgrades. See details in Intel® Trust Domain
Extensions (Intel® TDX) Module Base Architecture Specification, Chapter
"Handoff Versioning".
Ideally, the kernel needs to retrieve the handoff versions supported by
the current module and the new module and select a version supported by
both. But, since this implementation chooses to only support module
upgrades, simply request the current module to generate handoff data
using its highest supported version, expecting that the new module will
likely support it.
Note that only one CPU needs to call the TDX module's shutdown API.
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
---
v5:
- Massage changelog [Kai]
- Avoid "refers to the global copy while populating the tdx_sys_info
passed as a pointer" [Rick/Yilun]
v4:
- skip the whole handoff metadata if runtime updates are not supported
[Yilun]
v3:
- remove autogeneration stuff in the changelog
v2:
- add a comment about how handoff version is chosen.
- remove the first !ret in get_tdx_sys_info_handoff() as we edited the
auto-generated code anyway
- remove !! when determining whether a CPU is the primary one
- remove unnecessary if-break nesting in TDP_SHUTDOWN
---
arch/x86/include/asm/tdx_global_metadata.h | 5 +++++
arch/x86/virt/vmx/tdx/seamldr.c | 11 ++++++++++-
arch/x86/virt/vmx/tdx/tdx.c | 15 +++++++++++++++
arch/x86/virt/vmx/tdx/tdx.h | 3 +++
arch/x86/virt/vmx/tdx/tdx_global_metadata.c | 20 ++++++++++++++++++++
5 files changed, 53 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/tdx_global_metadata.h b/arch/x86/include/asm/tdx_global_metadata.h
index 40689c8dc67e..8a9ebd895e70 100644
--- a/arch/x86/include/asm/tdx_global_metadata.h
+++ b/arch/x86/include/asm/tdx_global_metadata.h
@@ -40,12 +40,17 @@ struct tdx_sys_info_td_conf {
u64 cpuid_config_values[128][2];
};
+struct tdx_sys_info_handoff {
+ u16 module_hv;
+};
+
struct tdx_sys_info {
struct tdx_sys_info_version version;
struct tdx_sys_info_features features;
struct tdx_sys_info_tdmr tdmr;
struct tdx_sys_info_td_ctrl td_ctrl;
struct tdx_sys_info_td_conf td_conf;
+ struct tdx_sys_info_handoff handoff;
};
#endif
diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index 771671b7755b..a8fd29818378 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -15,6 +15,7 @@
#include <asm/seamldr.h>
#include "seamcall_internal.h"
+#include "tdx.h"
/* P-SEAMLDR SEAMCALL leaf function */
#define P_SEAMLDR_INFO 0x8000000000000000
@@ -190,6 +191,7 @@ static struct seamldr_params *init_seamldr_params(const u8 *data, u32 size)
*/
enum module_update_state {
MODULE_UPDATE_START,
+ MODULE_UPDATE_SHUTDOWN,
MODULE_UPDATE_DONE,
};
@@ -229,8 +231,12 @@ static void ack_state(void)
static int do_seamldr_install_module(void *seamldr_params)
{
enum module_update_state newstate, curstate = MODULE_UPDATE_START;
+ int cpu = smp_processor_id();
+ bool primary;
int ret = 0;
+ primary = cpumask_first(cpu_online_mask) == cpu;
+
do {
/* Chill out and re-read update_data. */
cpu_relax();
@@ -239,7 +245,10 @@ static int do_seamldr_install_module(void *seamldr_params)
if (newstate != curstate) {
curstate = newstate;
switch (curstate) {
- /* TODO: add the update steps. */
+ case MODULE_UPDATE_SHUTDOWN:
+ if (primary)
+ ret = tdx_module_shutdown();
+ break;
default:
break;
}
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 172f6d4133b5..f87fad429f4e 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1176,6 +1176,21 @@ int tdx_enable(void)
}
EXPORT_SYMBOL_FOR_KVM(tdx_enable);
+int tdx_module_shutdown(void)
+{
+ struct tdx_module_args args = {};
+
+ /*
+ * Shut down the TDX module and prepare handoff data for the next
+ * TDX module. This SEAMCALL requires a handoff version. Use the
+ * module's handoff version, as it is the highest version the
+ * module can produce and is more likely to be supported by new
+ * modules as new modules likely have higher handoff version.
+ */
+ args.rcx = tdx_sysinfo.handoff.module_hv;
+ return seamcall_prerr(TDH_SYS_SHUTDOWN, &args);
+}
+
static bool is_pamt_page(unsigned long phys)
{
struct tdmr_info_list *tdmr_list = &tdx_tdmr_list;
diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
index 82bb82be8567..1c4da9540ae0 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_SYS_SHUTDOWN 52
/*
* SEAMCALL leaf:
@@ -118,4 +119,6 @@ struct tdmr_info_list {
int max_tdmrs; /* How many 'tdmr_info's are allocated */
};
+int tdx_module_shutdown(void);
+
#endif
diff --git a/arch/x86/virt/vmx/tdx/tdx_global_metadata.c b/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
index 4c9917a9c2c3..1b6f9b80b197 100644
--- a/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
+++ b/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
@@ -100,6 +100,19 @@ static int get_tdx_sys_info_td_conf(struct tdx_sys_info_td_conf *sysinfo_td_conf
return ret;
}
+static int get_tdx_sys_info_handoff(struct tdx_sys_info_handoff *sysinfo_handoff)
+{
+ int ret;
+ u64 val;
+
+ ret = read_sys_metadata_field(0x8900000100000000, &val);
+ if (ret)
+ return ret;
+
+ sysinfo_handoff->module_hv = val;
+ return 0;
+}
+
static int get_tdx_sys_info(struct tdx_sys_info *sysinfo)
{
int ret = 0;
@@ -116,5 +129,12 @@ static int get_tdx_sys_info(struct tdx_sys_info *sysinfo)
ret = ret ?: get_tdx_sys_info_td_ctrl(&sysinfo->td_ctrl);
ret = ret ?: get_tdx_sys_info_td_conf(&sysinfo->td_conf);
+ /*
+ * Don't treat a module that doesn't support update as a failure.
+ * Only read the metadata optionally.
+ */
+ if (tdx_supports_runtime_update(sysinfo))
+ ret = ret ?: get_tdx_sys_info_handoff(&sysinfo->handoff);
+
return ret;
}
--
2.47.3
^ permalink raw reply related
* [PATCH v6 12/22] x86/virt/tdx: Reset software states during TDX module shutdown
From: Chao Gao @ 2026-03-26 8:44 UTC (permalink / raw)
To: linux-kernel, linux-coco, kvm
Cc: binbin.wu, dan.j.williams, dave.hansen, ira.weiny, kai.huang, kas,
nik.borisov, paulmck, pbonzini, reinette.chatre, rick.p.edgecombe,
sagis, seanjc, tony.lindgren, vannapurve, vishal.l.verma,
yilun.xu, xiaoyao.li, yan.y.zhao, Chao Gao, Thomas Gleixner,
Ingo Molnar, Borislav Petkov, x86, H. Peter Anvin
In-Reply-To: <20260326084448.29947-1-chao.gao@intel.com>
The TDX module requires a one-time global initialization (TDH.SYS.INIT) and
per-CPU initialization (TDH.SYS.LP.INIT) before use. These initializations
are guarded by software flags to prevent repetition.
After TDX module updates, the new TDX module requires the same global and
per-CPU initializations, but the existing software flags prevent
re-initialization.
Reset all software flags guarding the initialization flows to allow the
global and per-CPU initializations to be triggered again after updates.
Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
---
v6:
- reset tdx_lp_initialized for offlined CPUs and update the comment
accordingly [Kai]
v5:
- add a comment to clarify why state access doesn't require holding a
lock. [Kai]
---
arch/x86/virt/vmx/tdx/tdx.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index f87fad429f4e..a2a46c734d5e 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -55,6 +55,8 @@ static struct tdmr_info_list tdx_tdmr_list;
static enum tdx_module_status_t tdx_module_status;
static DEFINE_MUTEX(tdx_module_lock);
+static bool sysinit_done;
+static int sysinit_ret;
/* All TDX-usable memory regions. Protected by mem_hotplug_lock. */
static LIST_HEAD(tdx_memlist);
@@ -70,8 +72,6 @@ static int try_init_module_global(void)
{
struct tdx_module_args args = {};
static DEFINE_RAW_SPINLOCK(sysinit_lock);
- static bool sysinit_done;
- static int sysinit_ret;
lockdep_assert_irqs_disabled();
@@ -1179,6 +1179,7 @@ EXPORT_SYMBOL_FOR_KVM(tdx_enable);
int tdx_module_shutdown(void)
{
struct tdx_module_args args = {};
+ int ret, cpu;
/*
* Shut down the TDX module and prepare handoff data for the next
@@ -1188,7 +1189,23 @@ int tdx_module_shutdown(void)
* modules as new modules likely have higher handoff version.
*/
args.rcx = tdx_sysinfo.handoff.module_hv;
- return seamcall_prerr(TDH_SYS_SHUTDOWN, &args);
+ ret = seamcall_prerr(TDH_SYS_SHUTDOWN, &args);
+ if (ret)
+ return ret;
+
+ tdx_module_status = TDX_MODULE_UNINITIALIZED;
+ sysinit_done = false;
+ sysinit_ret = 0;
+
+ /*
+ * Since the TDX module is shut down and gone, mark all CPUs
+ * (including offlined ones) as uninitialied. This is called in
+ * stop_machine() (where CPU hotplug is disabled), preventing
+ * races with other tdx_lp_initialized accesses.
+ */
+ for_each_possible_cpu(cpu)
+ per_cpu(tdx_lp_initialized, cpu) = false;
+ return 0;
}
static bool is_pamt_page(unsigned long phys)
--
2.47.3
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