x86, cpa: srlz cpa(), global flush tlb after splitting big page and before doing cpa (ad5ca55f) · Commits · 戴 / test

arch/x86/mm/pageattr.c

+38 −2

Original line number	Diff line number	Diff line
		@@ -35,6 +35,14 @@ struct cpa_data {
		int curpage;
		};

		/*
		* Serialize cpa() (for !DEBUG_PAGEALLOC which uses large identity mappings)
		* using cpa_lock. So that we don't allow any other cpu, with stale large tlb
		* entries change the page attribute in parallel to some other cpu
		* splitting a large page entry along with changing the attribute.
		*/
		static DEFINE_SPINLOCK(cpa_lock);

		#define CPA_FLUSHTLB 1
		#define CPA_ARRAY 2

		@@ -453,7 +461,13 @@ static int split_large_page(pte_t *kpte, unsigned long address)
		unsigned int i, level;
		pte_t pbase, tmp;
		pgprot_t ref_prot;
		struct page *base = alloc_pages(GFP_KERNEL, 0);
		struct page *base;

		if (!debug_pagealloc)
		spin_unlock(&cpa_lock);
		base = alloc_pages(GFP_KERNEL, 0);
		if (!debug_pagealloc)
		spin_lock(&cpa_lock);
		if (!base)
		return -ENOMEM;

		@@ -594,7 +608,25 @@ repeat:
		*/
		err = split_large_page(kpte, address);
		if (!err) {
		cpa->flags \|= CPA_FLUSHTLB;
		/*
		* Do a global flush tlb after splitting the large page
		* and before we do the actual change page attribute in the PTE.
		*
		* With out this, we violate the TLB application note, that says
		* "The TLBs may contain both ordinary and large-page
		* translations for a 4-KByte range of linear addresses. This
		* may occur if software modifies the paging structures so that
		* the page size used for the address range changes. If the two
		* translations differ with respect to page frame or attributes
		* (e.g., permissions), processor behavior is undefined and may
		* be implementation-specific."
		*
		* We do this global tlb flush inside the cpa_lock, so that we
		* don't allow any other cpu, with stale tlb entries change the
		* page attribute in parallel, that also falls into the
		* just split large page entry.
		*/
		flush_tlb_all();
		goto repeat;
		}

		@@ -686,7 +718,11 @@ static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias)
		if (cpa->flags & CPA_ARRAY)
		cpa->numpages = 1;

		if (!debug_pagealloc)
		spin_lock(&cpa_lock);
		ret = __change_page_attr(cpa, checkalias);
		if (!debug_pagealloc)
		spin_unlock(&cpa_lock);
		if (ret)
		return ret;

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