[SRU][J/gcp][PATCH 1/1] x86/sev: Make enc_dec_hypercall() accept a size instead of npages

[Khalid Elmously]

From: Steve Rutherford <srutherford at google.com>

BugLink: https://bugs.launchpad.net/bugs/2034894

enc_dec_hypercall() accepted a page count instead of a size, which
forced its callers to round up. As a result, non-page aligned
vaddrs caused pages to be spuriously marked as decrypted via the
encryption status hypercall, which in turn caused consistent
corruption of pages during live migration. Live migration requires
accurate encryption status information to avoid migrating pages
from the wrong perspective.

Fixes: 064ce6c550a0 ("mm: x86: Invoke hypercall when page encryption status is changed")
Signed-off-by: Steve Rutherford <srutherford at google.com>
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Reviewed-by: Tom Lendacky <thomas.lendacky at amd.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta at amd.com>
Tested-by: Ben Hillier <bhillier at google.com>
Cc: stable at vger.kernel.org
Link: https://lore.kernel.org/r/20230824223731.2055016-1-srutherford@google.com
Signed-off-by: Khalid Elmously <khalid.elmously at canonical.com>
(backported from commit ac3f9c9f1b37edaa7d1a9b908bc79d843955a1a2)
[ kmously: adjusted for different context in arch/x86/mm/mem_encrypt_amd.c ]
---
 arch/x86/include/asm/mem_encrypt.h |  6 +++---
 arch/x86/include/asm/set_memory.h  |  2 +-
 arch/x86/kernel/kvm.c              |  4 +---
 arch/x86/mm/mem_encrypt_amd.c      | 13 ++++++-------
 4 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
index efaaf66a2fead..e2f7fc54f8705 100644
--- a/arch/x86/include/asm/mem_encrypt.h
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -44,8 +44,8 @@ void __init sme_enable(struct boot_params *bp);
 
 int __init early_set_memory_decrypted(unsigned long vaddr, unsigned long size);
 int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size);
-void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages,
-					    bool enc);
+void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr,
+					    unsigned long size, bool enc);
 
 void __init mem_encrypt_free_decrypted_mem(void);
 
@@ -86,7 +86,7 @@ early_set_memory_decrypted(unsigned long vaddr, unsigned long size) { return 0;
 static inline int __init
 early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; }
 static inline void __init
-early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages, bool enc) {}
+early_set_mem_enc_dec_hypercall(unsigned long vaddr, unsigned long size, bool enc) {}
 
 static inline void mem_encrypt_free_decrypted_mem(void) { }
 
diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
index 872617542bbc0..5d411255b2c05 100644
--- a/arch/x86/include/asm/set_memory.h
+++ b/arch/x86/include/asm/set_memory.h
@@ -83,7 +83,7 @@ int set_pages_rw(struct page *page, int numpages);
 int set_direct_map_invalid_noflush(struct page *page);
 int set_direct_map_default_noflush(struct page *page);
 bool kernel_page_present(struct page *page);
-void notify_range_enc_status_changed(unsigned long vaddr, int npages, bool enc);
+void notify_range_enc_status_changed(unsigned long vaddr, unsigned long size, bool enc);
 
 extern int kernel_set_to_readonly;
 
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index dbab42d8af7ab..4fa324335d57f 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -931,10 +931,8 @@ static void __init kvm_init_platform(void)
 		 * Ensure that _bss_decrypted section is marked as decrypted in the
 		 * shared pages list.
 		 */
-		nr_pages = DIV_ROUND_UP(__end_bss_decrypted - __start_bss_decrypted,
-					PAGE_SIZE);
 		early_set_mem_enc_dec_hypercall((unsigned long)__start_bss_decrypted,
-						nr_pages, 0);
+						__end_bss_decrypted - __start_bss_decrypted, 0);
 
 		/*
 		 * If not booted using EFI, enable Live migration support.
diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
index c4332d56d683b..ff51890ce49f9 100644
--- a/arch/x86/mm/mem_encrypt_amd.c
+++ b/arch/x86/mm/mem_encrypt_amd.c
@@ -292,11 +292,10 @@ static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
 	return pfn;
 }
 
-void notify_range_enc_status_changed(unsigned long vaddr, int npages, bool enc)
+void notify_range_enc_status_changed(unsigned long vaddr, unsigned long size, bool enc)
 {
 #ifdef CONFIG_PARAVIRT
-	unsigned long sz = npages << PAGE_SHIFT;
-	unsigned long vaddr_end = vaddr + sz;
+	unsigned long vaddr_end = vaddr + size;
 
 	while (vaddr < vaddr_end) {
 		int psize, pmask, level;
@@ -316,7 +315,7 @@ void notify_range_enc_status_changed(unsigned long vaddr, int npages, bool enc)
 		psize = page_level_size(level);
 		pmask = page_level_mask(level);
 
-		notify_page_enc_status_changed(pfn, psize >> PAGE_SHIFT, enc);
+		notify_page_enc_status_changed(pfn, size, enc);
 
 		vaddr = (vaddr & pmask) + psize;
 	}
@@ -442,7 +441,7 @@ static int __init early_set_memory_enc_dec(unsigned long vaddr,
 
 	ret = 0;
 
-	notify_range_enc_status_changed(start, PAGE_ALIGN(size) >> PAGE_SHIFT, enc);
+	notify_range_enc_status_changed(start, size, enc);
 out:
 	__flush_tlb_all();
 	return ret;
@@ -458,9 +457,9 @@ int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size)
 	return early_set_memory_enc_dec(vaddr, size, true);
 }
 
-void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages, bool enc)
+void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, unsigned long size, bool enc)
 {
-	notify_range_enc_status_changed(vaddr, npages, enc);
+	notify_range_enc_status_changed(vaddr, size, enc);
 }
 
 /*
-- 
2.34.1