[RFC PATCH v2 12/20] x86: Add support for changing memory encryption attribute

[Tom Lendacky]

This patch adds support to be change the memory encryption attribute for
one or more memory pages.

Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
 arch/x86/include/asm/cacheflush.h  |    3 +
 arch/x86/include/asm/mem_encrypt.h |   13 ++++++
 arch/x86/mm/mem_encrypt.c          |   43 +++++++++++++++++++++
 arch/x86/mm/pageattr.c             |   75 ++++++++++++++++++++++++++++++++++++
 4 files changed, 134 insertions(+)

diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h
index 61518cf..bfb08e5 100644
--- a/arch/x86/include/asm/cacheflush.h
+++ b/arch/x86/include/asm/cacheflush.h
@@ -13,6 +13,7 @@
  * Executability : eXeutable, NoteXecutable
  * Read/Write    : ReadOnly, ReadWrite
  * Presence      : NotPresent
+ * Encryption    : ENCrypted, DECrypted
  *
  * Within a category, the attributes are mutually exclusive.
  *
@@ -48,6 +49,8 @@ int set_memory_ro(unsigned long addr, int numpages);
 int set_memory_rw(unsigned long addr, int numpages);
 int set_memory_np(unsigned long addr, int numpages);
 int set_memory_4k(unsigned long addr, int numpages);
+int set_memory_enc(unsigned long addr, int numpages);
+int set_memory_dec(unsigned long addr, int numpages);
 
 int set_memory_array_uc(unsigned long *addr, int addrinarray);
 int set_memory_array_wc(unsigned long *addr, int addrinarray);
diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
index 2785493..5616ed1 100644
--- a/arch/x86/include/asm/mem_encrypt.h
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -23,6 +23,9 @@ extern unsigned long sme_me_mask;
 
 u8 sme_get_me_loss(void);
 
+int sme_set_mem_enc(void *vaddr, unsigned long size);
+int sme_set_mem_dec(void *vaddr, unsigned long size);
+
 void __init sme_early_mem_enc(resource_size_t paddr,
 			      unsigned long size);
 void __init sme_early_mem_dec(resource_size_t paddr,
@@ -44,6 +47,16 @@ static inline u8 sme_get_me_loss(void)
 	return 0;
 }
 
+static inline int sme_set_mem_enc(void *vaddr, unsigned long size)
+{
+	return 0;
+}
+
+static inline int sme_set_mem_dec(void *vaddr, unsigned long size)
+{
+	return 0;
+}
+
 static inline void __init sme_early_mem_enc(resource_size_t paddr,
 					    unsigned long size)
 {
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index f35a646..b0f39c5 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -14,12 +14,55 @@
 #include <linux/mm.h>
 
 #include <asm/mem_encrypt.h>
+#include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 #include <asm/fixmap.h>
 
 /* Buffer used for early in-place encryption by BSP, no locking needed */
 static char me_early_buffer[PAGE_SIZE] __aligned(PAGE_SIZE);
 
+int sme_set_mem_enc(void *vaddr, unsigned long size)
+{
+	unsigned long addr, numpages;
+
+	if (!sme_me_mask)
+		return 0;
+
+	addr = (unsigned long)vaddr & PAGE_MASK;
+	numpages = PAGE_ALIGN(size) >> PAGE_SHIFT;
+
+	/*
+	 * The set_memory_xxx functions take an integer for numpages, make
+	 * sure it doesn't exceed that.
+	 */
+	if (numpages > INT_MAX)
+		return -EINVAL;
+
+	return set_memory_enc(addr, numpages);
+}
+EXPORT_SYMBOL_GPL(sme_set_mem_enc);
+
+int sme_set_mem_dec(void *vaddr, unsigned long size)
+{
+	unsigned long addr, numpages;
+
+	if (!sme_me_mask)
+		return 0;
+
+	addr = (unsigned long)vaddr & PAGE_MASK;
+	numpages = PAGE_ALIGN(size) >> PAGE_SHIFT;
+
+	/*
+	 * The set_memory_xxx functions take an integer for numpages, make
+	 * sure it doesn't exceed that.
+	 */
+	if (numpages > INT_MAX)
+		return -EINVAL;
+
+	return set_memory_dec(addr, numpages);
+}
+EXPORT_SYMBOL_GPL(sme_set_mem_dec);
+
 /*
  * This routine does not change the underlying encryption setting of the
  * page(s) that map this memory. It assumes that eventually the memory is
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 72c292d..0ba9382 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1728,6 +1728,81 @@ int set_memory_4k(unsigned long addr, int numpages)
 					__pgprot(0), 1, 0, NULL);
 }
 
+static int __set_memory_enc_dec(struct cpa_data *cpa)
+{
+	unsigned long addr;
+	int numpages;
+	int ret;
+
+	if (*cpa->vaddr & ~PAGE_MASK) {
+		*cpa->vaddr &= PAGE_MASK;
+
+		/* People should not be passing in unaligned addresses */
+		WARN_ON_ONCE(1);
+	}
+
+	addr = *cpa->vaddr;
+	numpages = cpa->numpages;
+
+	/* Must avoid aliasing mappings in the highmem code */
+	kmap_flush_unused();
+	vm_unmap_aliases();
+
+	ret = __change_page_attr_set_clr(cpa, 1);
+
+	/* Check whether we really changed something */
+	if (!(cpa->flags & CPA_FLUSHTLB))
+		goto out;
+
+	/*
+	 * On success we use CLFLUSH, when the CPU supports it to
+	 * avoid the WBINVD.
+	 */
+	if (!ret && static_cpu_has(X86_FEATURE_CLFLUSH))
+		cpa_flush_range(addr, numpages, 1);
+	else
+		cpa_flush_all(1);
+
+out:
+	return ret;
+}
+
+int set_memory_enc(unsigned long addr, int numpages)
+{
+	struct cpa_data cpa;
+
+	if (!sme_me_mask)
+		return 0;
+
+	memset(&cpa, 0, sizeof(cpa));
+	cpa.vaddr = &addr;
+	cpa.numpages = numpages;
+	cpa.mask_set = __pgprot(_PAGE_ENC);
+	cpa.mask_clr = __pgprot(0);
+	cpa.pgd = init_mm.pgd;
+
+	return __set_memory_enc_dec(&cpa);
+}
+EXPORT_SYMBOL(set_memory_enc);
+
+int set_memory_dec(unsigned long addr, int numpages)
+{
+	struct cpa_data cpa;
+
+	if (!sme_me_mask)
+		return 0;
+
+	memset(&cpa, 0, sizeof(cpa));
+	cpa.vaddr = &addr;
+	cpa.numpages = numpages;
+	cpa.mask_set = __pgprot(0);
+	cpa.mask_clr = __pgprot(_PAGE_ENC);
+	cpa.pgd = init_mm.pgd;
+
+	return __set_memory_enc_dec(&cpa);
+}
+EXPORT_SYMBOL(set_memory_dec);
+
 int set_pages_uc(struct page *page, int numpages)
 {
 	unsigned long addr = (unsigned long)page_address(page);