Messages in this thread |  | | Subject | Re: [PATCH v9 15/24] mm: Introduce __vm_normal_page() | From | Laurent Dufour <> | Date | Wed, 4 Apr 2018 18:26:44 +0200 |
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On 03/04/2018 21:39, Jerome Glisse wrote: > On Tue, Mar 13, 2018 at 06:59:45PM +0100, Laurent Dufour wrote: >> When dealing with the speculative fault path we should use the VMA's field >> cached value stored in the vm_fault structure. >> >> Currently vm_normal_page() is using the pointer to the VMA to fetch the >> vm_flags value. This patch provides a new __vm_normal_page() which is >> receiving the vm_flags flags value as parameter. >> >> Note: The speculative path is turned on for architecture providing support >> for special PTE flag. So only the first block of vm_normal_page is used >> during the speculative path. > > Might be a good idea to explicitly have SPECULATIVE Kconfig option depends > on ARCH_PTE_SPECIAL and a comment for !HAVE_PTE_SPECIAL in the function > explaining that speculative page fault should never reach that point.
Unfortunately there is no ARCH_PTE_SPECIAL in the config file, it is defined in the per architecture header files. So I can't do anything in the Kconfig file
However, I can check that at build time, and doing such a check in __vm_normal_page sounds to be a good place, like that:
@@ -869,6 +870,14 @@ struct page *__vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
/* !HAVE_PTE_SPECIAL case follows: */
+#ifdef CONFIG_SPECULATIVE_PAGE_FAULT + /* This part should never get called when the speculative page fault + * handler is turned on. This is mainly because we can't rely on + * vm_start. + */ +#error CONFIG_SPECULATIVE_PAGE_FAULT requires HAVE_PTE_SPECIAL +#endif + if (unlikely(vma_flags & (VM_PFNMAP|VM_MIXEDMAP))) { if (vma_flags & VM_MIXEDMAP) { if (!pfn_valid(pfn))
Thanks, Laurent.
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