Re: [RFC Part1 PATCH v3 15/17] x86: Add support for changing memory encryption attribute in early boot

Hi Boris,


On 8/28/17 5:51 AM, Borislav Petkov wrote:

[..]

+static int __init early_set_memory_enc_dec(resource_size_t paddr,

quoted

+					   unsigned long size, bool enc)
+{
+	unsigned long vaddr, vaddr_end, vaddr_next;
+	unsigned long psize, pmask;
+	int split_page_size_mask;
+	pte_t *kpte;
+	int level;
+
+	vaddr = (unsigned long)__va(paddr);
+	vaddr_next = vaddr;
+	vaddr_end = vaddr + size;
+
+	/*
+	 * We are going to change the physical page attribute from C=1 to C=0
+	 * or vice versa. Flush the caches to ensure that data is written into
+	 * memory with correct C-bit before we change attribute.
+	 */
+	clflush_cache_range(__va(paddr), size);
+
+	for (; vaddr < vaddr_end; vaddr = vaddr_next) {
+		kpte = lookup_address(vaddr, &level);
+		if (!kpte || pte_none(*kpte))
+			return 1;

Return before flushing TLBs? Perhaps you mean

			ret = 1;
			goto out;

here and out does

	__flush_tlb_all();
	return ret;

thanks, good catch. I will fix in next rev.

-Brijesh