[PATCH 6.4 065/800] x86/mm: Allow guest.enc_status_change_prepare() to fail

Greg Kroah-Hartman
2023-07-16T19:55:50Z

From: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

[ Upstream commit 3f6819dd192ef4f0c568ec3e9d6d408b3fa1ad3d ]

TDX code is going to provide guest.enc_status_change_prepare() that is
able to fail. TDX will use the call to convert the GPA range from shared
to private. This operation can fail.

Add a way to return an error from the callback.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Link: https://lore.kernel.org/all/20230606095622.1939-2-kirill.shutemov%40linux.intel.com
Stable-dep-of: 195edce08b63 ("x86/tdx: Fix race between set_memory_encrypted() and load_unaligned_zeropad()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/include/asm/x86_init.h | 2 +-
arch/x86/kernel/x86_init.c | 2 +-
arch/x86/mm/mem_encrypt_amd.c | 4 +++-
arch/x86/mm/pat/set_memory.c | 3 ++-
4 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 88085f369ff6f..1ca9701917c55 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -150,7 +150,7 @@ struct x86_init_acpi {
* @enc_cache_flush_required Returns true if a cache flush is needed before changing page encryption status
*/
struct x86_guest {
- void (*enc_status_change_prepare)(unsigned long vaddr, int npages, bool enc);
+ bool (*enc_status_change_prepare)(unsigned long vaddr, int npages, bool enc);
bool (*enc_status_change_finish)(unsigned long vaddr, int npages, bool enc);
bool (*enc_tlb_flush_required)(bool enc);
bool (*enc_cache_flush_required)(void);
diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index d82f4fa2f1bfe..f230d4d7d8eb4 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -130,7 +130,7 @@ struct x86_cpuinit_ops x86_cpuinit = {

static void default_nmi_init(void) { };

-static void enc_status_change_prepare_noop(unsigned long vaddr, int npages, bool enc) { }
+static bool enc_status_change_prepare_noop(unsigned long vaddr, int npages, bool enc) { return true; }
static bool enc_status_change_finish_noop(unsigned long vaddr, int npages, bool enc) { return false; }
static bool enc_tlb_flush_required_noop(bool enc) { return false; }
static bool enc_cache_flush_required_noop(void) { return false; }
diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
index e0b51c09109f6..4f95c449a406e 100644
--- a/arch/x86/mm/mem_encrypt_amd.c
+++ b/arch/x86/mm/mem_encrypt_amd.c
@@ -319,7 +319,7 @@ static void enc_dec_hypercall(unsigned long vaddr, int npages, bool enc)
#endif
}

-static void amd_enc_status_change_prepare(unsigned long vaddr, int npages, bool enc)
+static bool amd_enc_status_change_prepare(unsigned long vaddr, int npages, bool enc)
{
/*
* To maintain the security guarantees of SEV-SNP guests, make sure
@@ -327,6 +327,8 @@ static void amd_enc_status_change_prepare(unsigned long vaddr, int npages, bool
*/
if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP) && !enc)
snp_set_memory_shared(vaddr, npages);
+
+ return true;
}

/* Return true unconditionally: return value doesn't matter for the SEV side */
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 7159cf7876130..b8f48ebe753c7 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -2151,7 +2151,8 @@ static int __set_memory_enc_pgtable(unsigned long addr, int numpages, bool enc)
cpa_flush(&cpa, x86_platform.guest.enc_cache_flush_required());

/* Notify hypervisor that we are about to set/clr encryption attribute. */
- x86_platform.guest.enc_status_change_prepare(addr, numpages, enc);
+ if (!x86_platform.guest.enc_status_change_prepare(addr, numpages, enc))
+ return -EIO;

ret = __change_page_attr_set_clr(&cpa, 1);

--
2.39.2