On Sun, 7 Mar 2021 11:16:24 -0800 Andy Lutomirski <l...@amacapital.net> wrote:
> > > > >> Some programs may use read(2), write(2), etc as ways to check if > > > > >> memory is valid without getting a signal. They might not want > > > > >> signals, which means that this feature might need to be > > > > >> configurable. > > > > > > > > > > That sounds like an appalling hack. If users need such a mechanism > > > > > we should create some better way to do that. > > > > > > > > > > > > > Appalling hack or not, it works. So, if we’re going to send a signal to > > > > user code that looks like it originated from a bina fide architectural > > > > recoverable fault, it needs to be recoverable. A load from a failed > > > > NVDIMM page is such a fault. A *kernel* load is not. So we need to > > > > distinguish it somehow. > > > > > > Sorry for my previous mis-understanding, and i have some questions: > > > if programs use read,write to check if if memory is valid, does it really > > > want to cover the poison case? > > I don't know. > > > > When for such a case, an error is returned, can the program realize it's > > > hwposion issue not other software error and process correctly? > > Again, I don't know. But changing the API like this seems potentialy > dangerous and needs to be done with care. > > > > > > > if this is the proper action, the original posion flow in current code > > > from read and write need to change too. > > > > > > > Sorry, another question: > > When programs use read(2), write(2) as ways to check if memory is valid, > > does it really want to check if the user page the program provided is > > valid, not the destination or disk space valid? > > They may well be trying to see if their memory is valid. Thanks for your reply, and I don't know what to do. For current code, if user program write to a block device(maybe a test try) and if its user copy page corrupt when in kernel copy, the process is killed with a SIGBUS. And for the page fault case in this thread, the process is error returned. -- Thanks! Aili Yao
