Re: [PATCH 2/2] x86/tdx: Accept hotplugged memory before online

[Marc-André Lureau]

Hi

On Wed, Mar 25, 2026 at 2:04 AM Edgecombe, Rick P
<rick.p.edgecombe@xxxxxxxxx> wrote:
>
> On Tue, 2026-03-24 at 19:21 +0400, Marc-André Lureau wrote:
> > In TDX guests, hotplugged memory (e.g., via virtio-mem) is never
> > accepted before use. The first access triggers a fatal "SEPT entry in
> > PENDING state" EPT violation and KVM terminates the guest.
> >
> > Fix this by registering a MEM_GOING_ONLINE memory hotplug notifier that
> > calls tdx_accept_memory() for the range being onlined.
> >
> > The notifier returns NOTIFY_BAD on acceptance failure, preventing the
> > memory from going online.
>
> 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.