[RFC PATCH v1 10/10] mm: x86: Invoke hypercall when page encryption status is changed

["Singh, Brijesh" <brijesh.singh@amd.com>]

Invoke a hypercall when a memory region is changed from encrypted ->
decrypted and vice versa. Hypervisor need to know the page encryption
status during the guest migration.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 arch/x86/include/asm/mem_encrypt.h |  3 ++
 arch/x86/mm/mem_encrypt.c          | 45 +++++++++++++++++++++++++++++-
 arch/x86/mm/pageattr.c             | 15 ++++++++++
 3 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
index 616f8e637bc3..3f43cfdd0209 100644
--- a/arch/x86/include/asm/mem_encrypt.h
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -97,4 +97,7 @@ extern char __start_bss_decrypted[], __end_bss_decrypted[], __start_bss_decrypte
 
 #endif	/* __ASSEMBLY__ */
 
+extern void set_memory_enc_dec_hypercall(unsigned long vaddr,
+					 unsigned long size, bool enc);
+
 #endif	/* __X86_MEM_ENCRYPT_H__ */
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 385afa2b9e17..24261b58ac99 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -18,6 +18,7 @@
 #include <linux/dma-direct.h>
 #include <linux/swiotlb.h>
 #include <linux/mem_encrypt.h>
+#include <linux/kvm_para.h>
 
 #include <asm/tlbflush.h>
 #include <asm/fixmap.h>
@@ -28,6 +29,7 @@
 #include <asm/processor-flags.h>
 #include <asm/msr.h>
 #include <asm/cmdline.h>
+#include <asm/kvm_para.h>
 
 #include "mm_internal.h"
 
@@ -195,6 +197,45 @@ void __init sme_early_init(void)
 		swiotlb_force = SWIOTLB_FORCE;
 }
 
+void set_memory_enc_dec_hypercall(unsigned long vaddr, unsigned long sz, bool enc)
+{
+	unsigned long vaddr_end, vaddr_next;
+
+	vaddr_end = vaddr + sz;
+
+	for (; vaddr < vaddr_end; vaddr = vaddr_next) {
+		int psize, pmask, level;
+		unsigned long pfn;
+		pte_t *kpte;
+
+		kpte = lookup_address(vaddr, &level);
+		if (!kpte || pte_none(*kpte))
+			return;
+
+		switch (level) {
+		case PG_LEVEL_4K:
+			pfn = pte_pfn(*kpte);
+			break;
+		case PG_LEVEL_2M:
+			pfn = pmd_pfn(*(pmd_t *)kpte);
+			break;
+		case PG_LEVEL_1G:
+			pfn = pud_pfn(*(pud_t *)kpte);
+			break;
+		default:
+			return;
+		}
+
+		psize = page_level_size(level);
+		pmask = page_level_mask(level);
+
+		kvm_sev_hypercall3(KVM_HC_PAGE_ENC_STATUS,
+				   pfn << PAGE_SHIFT, psize >> PAGE_SHIFT, enc);
+
+		vaddr_next = (vaddr & pmask) + psize;
+	}
+}
+
 static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 {
 	pgprot_t old_prot, new_prot;
@@ -252,12 +293,13 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 static int __init early_set_memory_enc_dec(unsigned long vaddr,
 					   unsigned long size, bool enc)
 {
-	unsigned long vaddr_end, vaddr_next;
+	unsigned long vaddr_end, vaddr_next, start;
 	unsigned long psize, pmask;
 	int split_page_size_mask;
 	int level, ret;
 	pte_t *kpte;
 
+	start = vaddr;
 	vaddr_next = vaddr;
 	vaddr_end = vaddr + size;
 
@@ -308,6 +350,7 @@ static int __init early_set_memory_enc_dec(unsigned long vaddr,
 
 	ret = 0;
 
+	set_memory_enc_dec_hypercall(start, size, enc);
 out:
 	__flush_tlb_all();
 	return ret;
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 4c570612e24e..b1a68879f66d 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -25,6 +25,7 @@
 #include <asm/proto.h>
 #include <asm/pat.h>
 #include <asm/set_memory.h>
+#include <asm/mem_encrypt.h>
 
 #include "mm_internal.h"
 
@@ -2019,6 +2020,12 @@ int set_memory_global(unsigned long addr, int numpages)
 				    __pgprot(_PAGE_GLOBAL), 0);
 }
 
+void __attribute__((weak)) set_memory_enc_dec_hypercall(unsigned long addr,
+							unsigned long size,
+							bool enc)
+{
+}
+
 static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
 {
 	struct cpa_data cpa;
@@ -2059,6 +2066,14 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
 	 */
 	cpa_flush(&cpa, 0);
 
+	/*
+	 * When SEV is active, notify hypervisor that a given memory range is mapped
+	 * encrypted or decrypted. Hypervisor will use this information during
+	 * the VM migration.
+	 */
+	if (sev_active())
+		set_memory_enc_dec_hypercall(addr, numpages << PAGE_SHIFT, enc);
+
 	return ret;
 }
 
-- 
2.17.1