On Thu, May 9, 2024 at 2:30 PM John Hubbard <jhubb...@nvidia.com> wrote: > > On 5/9/24 1:39 PM, Axel Rasmussen wrote: > > For real MCEs, various architectures print log messages when poisoned > > memory is accessed (which results in a SIGBUS). These messages can be > > important for users to understand the issue. > > > > On the other hand, we have the userfaultfd UFFDIO_POISON operation, > > which can "simulate" memory poisoning. That particular process will get > > SIGBUS on access to the memory, but this effect is tied to an MM, rather > > than being global like a real poison event. So, we don't want to log > > about this case to the global kernel log; instead, let the process > > itself log or whatever else it wants to do. This avoids spamming the > > kernel log, and avoids e.g. drowning out real events with simulated > > ones. > > > > To identify this situation, add a new VM_FAULT_HWPOISON_SIM flag. This > > is expected to be set *in addition to* one of the existing > > VM_FAULT_HWPOISON or VM_FAULT_HWPOISON_LARGE flags (which are mutually > > exclusive). > > > > Signed-off-by: Axel Rasmussen <axelrasmus...@google.com> > > --- > > arch/parisc/mm/fault.c | 7 +++++-- > > arch/powerpc/mm/fault.c | 6 ++++-- > > arch/x86/mm/fault.c | 6 ++++-- > > include/linux/mm_types.h | 5 +++++ > > mm/hugetlb.c | 3 ++- > > mm/memory.c | 2 +- > > 6 files changed, 21 insertions(+), 8 deletions(-) > > > > This completely fixes the uffd-unit-test behavior, I just did a quick > test run to be sure as well. > > Reviewed-by: John Hubbard <jhubb...@nvidia.com>
Thanks John! And, no problem about the other patch, they aren't functionally dependent, I just hoped to save Andrew dealing with the small merge conflict. :) I'll base a v2 on mm-unstable directly and that should clear everything up. > > thanks, > -- > John Hubbard > NVIDIA > > > > diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c > > index c39de84e98b0..e5370bcadf27 100644 > > --- a/arch/parisc/mm/fault.c > > +++ b/arch/parisc/mm/fault.c > > @@ -400,9 +400,12 @@ void do_page_fault(struct pt_regs *regs, unsigned long > > code, > > #ifdef CONFIG_MEMORY_FAILURE > > if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { > > unsigned int lsb = 0; > > - printk(KERN_ERR > > + > > + if (!(fault & VM_FAULT_HWPOISON_SIM)) { > > + pr_err( > > "MCE: Killing %s:%d due to hardware memory corruption fault at > > %08lx\n", > > - tsk->comm, tsk->pid, address); > > + tsk->comm, tsk->pid, address); > > + } > > /* > > * Either small page or large page may be poisoned. > > * In other words, VM_FAULT_HWPOISON_LARGE and > > diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c > > index 53335ae21a40..ac5e8a3c7fba 100644 > > --- a/arch/powerpc/mm/fault.c > > +++ b/arch/powerpc/mm/fault.c > > @@ -140,8 +140,10 @@ static int do_sigbus(struct pt_regs *regs, unsigned > > long address, > > if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { > > unsigned int lsb = 0; /* shutup gcc */ > > > > - pr_err("MCE: Killing %s:%d due to hardware memory corruption > > fault at %lx\n", > > - current->comm, current->pid, address); > > + if (!(fault & VM_FAULT_HWPOISON_SIM)) { > > + pr_err("MCE: Killing %s:%d due to hardware memory > > corruption fault at %lx\n", > > + current->comm, current->pid, address); > > + } > > > > if (fault & VM_FAULT_HWPOISON_LARGE) > > lsb = > > hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > > index e4f3c7721f45..16d077a3ad14 100644 > > --- a/arch/x86/mm/fault.c > > +++ b/arch/x86/mm/fault.c > > @@ -928,9 +928,11 @@ do_sigbus(struct pt_regs *regs, unsigned long > > error_code, unsigned long address, > > struct task_struct *tsk = current; > > unsigned lsb = 0; > > > > - pr_err_ratelimited( > > + if (!(fault & VM_FAULT_HWPOISON_SIM)) { > > + pr_err_ratelimited( > > "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", > > - tsk->comm, tsk->pid, address); > > + tsk->comm, tsk->pid, address); > > + } > > if (fault & VM_FAULT_HWPOISON_LARGE) > > lsb = > > hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); > > if (fault & VM_FAULT_HWPOISON) > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > > index 5240bd7bca33..7f8fc3efc5b2 100644 > > --- a/include/linux/mm_types.h > > +++ b/include/linux/mm_types.h > > @@ -1226,6 +1226,9 @@ typedef __bitwise unsigned int vm_fault_t; > > * @VM_FAULT_HWPOISON_LARGE: Hit poisoned large page. Index encoded > > * in upper bits > > * @VM_FAULT_SIGSEGV: segmentation fault > > + * @VM_FAULT_HWPOISON_SIM Hit poisoned, PTE marker; this indicates a > > + * simulated poison (e.g. via usefaultfd's I'll also fix this small typo in a v2. :P > > + * UFFDIO_POISON), not a "real" hwerror. > > * @VM_FAULT_NOPAGE: ->fault installed the pte, not return > > page > > * @VM_FAULT_LOCKED: ->fault locked the returned page > > * @VM_FAULT_RETRY: ->fault blocked, must retry > > @@ -1245,6 +1248,7 @@ enum vm_fault_reason { > > VM_FAULT_HWPOISON = (__force vm_fault_t)0x000010, > > VM_FAULT_HWPOISON_LARGE = (__force vm_fault_t)0x000020, > > VM_FAULT_SIGSEGV = (__force vm_fault_t)0x000040, > > + VM_FAULT_HWPOISON_SIM = (__force vm_fault_t)0x000080, > > VM_FAULT_NOPAGE = (__force vm_fault_t)0x000100, > > VM_FAULT_LOCKED = (__force vm_fault_t)0x000200, > > VM_FAULT_RETRY = (__force vm_fault_t)0x000400, > > @@ -1270,6 +1274,7 @@ enum vm_fault_reason { > > { VM_FAULT_HWPOISON, "HWPOISON" }, \ > > { VM_FAULT_HWPOISON_LARGE, "HWPOISON_LARGE" }, \ > > { VM_FAULT_SIGSEGV, "SIGSEGV" }, \ > > + { VM_FAULT_HWPOISON_SIM, "HWPOISON_SIM" }, \ > > { VM_FAULT_NOPAGE, "NOPAGE" }, \ > > { VM_FAULT_LOCKED, "LOCKED" }, \ > > { VM_FAULT_RETRY, "RETRY" }, \ > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > index 65456230cc71..2b4e0173e806 100644 > > --- a/mm/hugetlb.c > > +++ b/mm/hugetlb.c > > @@ -6485,7 +6485,8 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct > > vm_area_struct *vma, > > pte_marker_get(pte_to_swp_entry(entry)); > > > > if (marker & PTE_MARKER_POISONED) { > > - ret = VM_FAULT_HWPOISON_LARGE | > > + ret = VM_FAULT_HWPOISON_SIM | > > + VM_FAULT_HWPOISON_LARGE | > > VM_FAULT_SET_HINDEX(hstate_index(h)); > > goto out_mutex; > > } > > diff --git a/mm/memory.c b/mm/memory.c > > index d2155ced45f8..29a833b996ae 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -3910,7 +3910,7 @@ static vm_fault_t handle_pte_marker(struct vm_fault > > *vmf) > > > > /* Higher priority than uffd-wp when data corrupted */ > > if (marker & PTE_MARKER_POISONED) > > - return VM_FAULT_HWPOISON; > > + return VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_SIM; > > > > if (pte_marker_entry_uffd_wp(entry)) > > return pte_marker_handle_uffd_wp(vmf); > >