Re: [RFC PATCH v2 15/32] x86: Add support for changing memory encryption attribute in early boot

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Hi Boris,

On 03/24/2017 12:12 PM, Borislav Petkov wrote:
 }

+static inline int __init early_set_memory_decrypted(void *addr,
+						    unsigned long size)
+{
+	return 1;
	^^^^^^^^

return 1 when !CONFIG_AMD_MEM_ENCRYPT ?

The non-early variants return 0.


I will fix it and use the same return value.

+}
+
+static inline int __init early_set_memory_encrypted(void *addr,
+						    unsigned long size)
+{
+	return 1;
+}
+
 #define __sme_pa		__pa

+	unsigned long pfn, npages;
+	unsigned long addr = (unsigned long)vaddr & PAGE_MASK;
+
+	/* We are going to change the physical page attribute from C=1 to C=0.
+	 * Flush the caches to ensure that all the data with C=1 is flushed to
+	 * memory. Any caching of the vaddr after function returns will
+	 * use C=0.
+	 */

Kernel comments style is:

	/*
	 * A sentence ending with a full-stop.
	 * Another sentence. ...
	 * More sentences. ...
	 */


I will update to use kernel comment style.


+	clflush_cache_range(vaddr, size);
+
+	npages = PAGE_ALIGN(size) >> PAGE_SHIFT;
+	pfn = slow_virt_to_phys((void *)addr) >> PAGE_SHIFT;
+
+	return kernel_map_pages_in_pgd(init_mm.pgd, pfn, addr, npages,
+					flags & ~sme_me_mask);
+
+}
+
+int __init early_set_memory_decrypted(void *vaddr, unsigned long size)
+{
+	unsigned long flags = get_pte_flags((unsigned long)vaddr);

So this does lookup_address()...

+	return early_set_memory_enc_dec(vaddr, size, flags & ~sme_me_mask);

... and this does it too in slow_virt_to_phys(). So you do it twice per
vaddr.

So why don't you define a __slow_virt_to_phys() helper - notice
the "__" - which returns flags in its second parameter and which
slow_virt_to_phys() calls with a NULL second parameter in the other
cases?


I will look into creating a helper function. thanks

-Brijesh
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