linux-kernel - [PATCH v7 22/36] x86/mm: Add support for changing the memory encryption attribute

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Date:   Fri, 16 Jun 2017 13:54:00 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, xen-devel@...ts.xen.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org
Cc:     Brijesh Singh <brijesh.singh@....com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Alexander Potapenko <glider@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Joerg Roedel <joro@...tes.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Dave Young <dyoung@...hat.com>, Rik van Riel <riel@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Juergen Gross <jgross@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH v7 22/36] x86/mm: Add support for changing the memory
 encryption attribute

Add support for changing the memory encryption attribute for one or more
memory pages. This will be useful when we have to change the AP trampoline
area to not be encrypted. Or when we need to change the SWIOTLB area to
not be encrypted in support of devices that can't support the encryption
mask range.

Reviewed-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/include/asm/set_memory.h |    3 ++
 arch/x86/mm/pageattr.c            |   62 +++++++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
index eaec6c3..cd71273 100644
--- a/arch/x86/include/asm/set_memory.h
+++ b/arch/x86/include/asm/set_memory.h
@@ -11,6 +11,7 @@
  * Executability : eXeutable, NoteXecutable
  * Read/Write    : ReadOnly, ReadWrite
  * Presence      : NotPresent
+ * Encryption    : Encrypted, Decrypted
  *
  * Within a category, the attributes are mutually exclusive.
  *
@@ -42,6 +43,8 @@
 int set_memory_wb(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_encrypted(unsigned long addr, int numpages);
+int set_memory_decrypted(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/mm/pageattr.c b/arch/x86/mm/pageattr.c
index e7d3866..d9e09fb 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1769,6 +1769,68 @@ int set_memory_4k(unsigned long addr, int numpages)
 					__pgprot(0), 1, 0, NULL);
 }
 
+static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
+{
+	struct cpa_data cpa;
+	unsigned long start;
+	int ret;
+
+	/* Nothing to do if the SME is not active */
+	if (!sme_active())
+		return 0;
+
+	/* Should not be working on unaligned addresses */
+	if (WARN_ONCE(addr & ~PAGE_MASK, "misaligned address: %#lx\n", addr))
+		addr &= PAGE_MASK;
+
+	start = addr;
+
+	memset(&cpa, 0, sizeof(cpa));
+	cpa.vaddr = &addr;
+	cpa.numpages = numpages;
+	cpa.mask_set = enc ? __pgprot(_PAGE_ENC) : __pgprot(0);
+	cpa.mask_clr = enc ? __pgprot(0) : __pgprot(_PAGE_ENC);
+	cpa.pgd = init_mm.pgd;
+
+	/* Must avoid aliasing mappings in the highmem code */
+	kmap_flush_unused();
+	vm_unmap_aliases();
+
+	/*
+	 * Before changing the encryption attribute, we need to flush caches.
+	 */
+	if (static_cpu_has(X86_FEATURE_CLFLUSH))
+		cpa_flush_range(start, numpages, 1);
+	else
+		cpa_flush_all(1);
+
+	ret = __change_page_attr_set_clr(&cpa, 1);
+
+	/*
+	 * After changing the encryption attribute, we need to flush TLBs
+	 * again in case any speculative TLB caching occurred (but no need
+	 * to flush caches again).  We could just use cpa_flush_all(), but
+	 * in case TLB flushing gets optimized in the cpa_flush_range()
+	 * path use the same logic as above.
+	 */
+	if (static_cpu_has(X86_FEATURE_CLFLUSH))
+		cpa_flush_range(start, numpages, 0);
+	else
+		cpa_flush_all(0);
+
+	return ret;
+}
+
+int set_memory_encrypted(unsigned long addr, int numpages)
+{
+	return __set_memory_enc_dec(addr, numpages, true);
+}
+
+int set_memory_decrypted(unsigned long addr, int numpages)
+{
+	return __set_memory_enc_dec(addr, numpages, false);
+}
+
 int set_pages_uc(struct page *page, int numpages)
 {
 	unsigned long addr = (unsigned long)page_address(page);