On Thu, Sep 06, 2018 at 05:01:25PM +0000, Nadav Amit wrote: > In addition, there might be a couple of issues with your fix: It boots on my box ;-) > 1. __set_pte_vaddr() is not used exclusive by set_fixmap(). This means > the warning might be wrong, but also means that these code patches (Xen’s > set_pte_mfn(), CPU-entry-area setup) needs to be checked. And as you said > before, someone might use this function for other purposes as well. CEA is fine, that actually needs it too. The one thing I missed out on earlier is the below chunk, that is no longer needed now that cea_set_pte() actually does the right thing. diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c index b7b01d762d32..14ad97fa0749 100644 --- a/arch/x86/events/intel/ds.c +++ b/arch/x86/events/intel/ds.c @@ -293,12 +293,6 @@ static void ds_update_cea(void *cea, void *addr, size_t size, pgprot_t prot) preempt_disable(); for (; msz < size; msz += PAGE_SIZE, pa += PAGE_SIZE, cea += PAGE_SIZE) cea_set_pte(cea, pa, prot); - - /* - * This is a cross-CPU update of the cpu_entry_area, we must shoot down - * all TLB entries for it. - */ - flush_tlb_kernel_range(start, start + size); preempt_enable(); } @@ -310,8 +304,6 @@ static void ds_clear_cea(void *cea, size_t size) preempt_disable(); for (; msz < size; msz += PAGE_SIZE, cea += PAGE_SIZE) cea_set_pte(cea, 0, PAGE_NONE); - - flush_tlb_kernel_range(start, start + size); preempt_enable(); } > 2. Printing the virtual address can break KASLR. Local KASLR is a myth.. but sure, we can fix the print. > 3. The WARN() can introduce some overhead since checking if IRQs are > disabled takes considerably long time. Perhaps VM_WARN() or something is > better. I realize this code-path is not on the hot-path though... Yeah, if it triggers you have bigger problems. We can make it WARN_ONCE() I suppose. > 4. I guess flush_tlb_kernel_range() should also have something like > VM_WARN_ON(irqs_disabled()), just as an additional general sanity check. It has, it's hidden in kernel/smp.c:smp_call_function_many(). > Let me know if you want me to make these changes and include your patch in > the set. The set is no longer needed. text_poke() is fine and correct with this one patch.
