On 01/04/2018 08:16 PM, Yisheng Xie wrote: >> === Page Table Poisoning === >> >> KAISER has two copies of the page tables: one for the kernel and >> one for when running in userspace. > > So, we have 2 page table, thinking about this case: > If _ONE_ process includes _TWO_ threads, one run in user space, the other > run in kernel, they can run in one core with Hyper-Threading, right? Yes. > So both userspace and kernel space is valid, right? And for one core > with Hyper-Threading, they may share TLB, so the timing problem > described in the paper may still exist? No. The TLB is managed per logical CPU (hyperthread), as is the CR3 register that points to the page tables. Two threads running the same process might use the same CR3 _value_, but that does not mean they share TLB entries. One thread *can* be in the kernel with the kernel page tables while the other is in userspace with the user page tables active. They will even use a different PCID/ASID for the same page tables normally. > Can this case still be protected by KAISER? Yes. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
