On Wed, Jan 25, 2023, Kirill A. Shutemov wrote: > On Wed, Jan 25, 2023 at 12:20:26AM +0000, Sean Christopherson wrote: > > On Tue, Jan 24, 2023, Liam Merwick wrote: > > > On 14/01/2023 00:37, Sean Christopherson wrote: > > > > On Fri, Dec 02, 2022, Chao Peng wrote: > > > > > This patch series implements KVM guest private memory for confidential > > > > > computing scenarios like Intel TDX[1]. If a TDX host accesses > > > > > TDX-protected guest memory, machine check can happen which can further > > > > > crash the running host system, this is terrible for multi-tenant > > > > > configurations. The host accesses include those from KVM userspace like > > > > > QEMU. This series addresses KVM userspace induced crash by introducing > > > > > new mm and KVM interfaces so KVM userspace can still manage guest memory > > > > > via a fd-based approach, but it can never access the guest memory > > > > > content. > > > > > > > > > > The patch series touches both core mm and KVM code. I appreciate > > > > > Andrew/Hugh and Paolo/Sean can review and pick these patches. Any other > > > > > reviews are always welcome. > > > > > - 01: mm change, target for mm tree > > > > > - 02-09: KVM change, target for KVM tree > > > > > > > > A version with all of my feedback, plus reworked versions of Vishal's selftest, > > > > is available here: > > > > > > > > git@xxxxxxxxxx:sean-jc/linux.git x86/upm_base_support > > > > > > > > It compiles and passes the selftest, but it's otherwise barely tested. There are > > > > a few todos (2 I think?) and many of the commits need changelogs, i.e. it's still > > > > a WIP. > > > > > > > > > > When running LTP (https://github.com/linux-test-project/ltp) on the v10 > > > bits (and also with Sean's branch above) I encounter the following NULL > > > pointer dereference with testcases/kernel/syscalls/madvise/madvise01 > > > (100% reproducible). > > > > > > It appears that in restrictedmem_error_page() > > > inode->i_mapping->private_data is NULL in the > > > list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) but I > > > don't know why. > > > > Kirill, can you take a look? Or pass the buck to someone who can? :-) > > The patch below should help. > > diff --git a/mm/restrictedmem.c b/mm/restrictedmem.c > index 15c52301eeb9..39ada985c7c0 100644 > --- a/mm/restrictedmem.c > +++ b/mm/restrictedmem.c > @@ -307,14 +307,29 @@ void restrictedmem_error_page(struct page *page, struct address_space *mapping) > > spin_lock(&sb->s_inode_list_lock); > list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) { > - struct restrictedmem *rm = inode->i_mapping->private_data; > struct restrictedmem_notifier *notifier; > - struct file *memfd = rm->memfd; > + struct restrictedmem *rm; > unsigned long index; > + struct file *memfd; > > - if (memfd->f_mapping != mapping) > + if (atomic_read(&inode->i_count)) Kirill, should this be if (!atomic_read(&inode->i_count)) continue; i.e. skip unreferenced inodes, not skip referenced inodes?
