[PATCH 6.12.y] x86/sev: Guard sev_evict_cache() with CONFIG_AMD_MEM_ENCRYPT

[Sasha Levin <sashal@kernel.org>]

From: Tom Lendacky <thomas.lendacky@amd.com>

[ Upstream commit 7f830e126dc357fc086905ce9730140fd4528d66 ]

The sev_evict_cache() is guest-related code and should be guarded by
CONFIG_AMD_MEM_ENCRYPT, not CONFIG_KVM_AMD_SEV.

CONFIG_AMD_MEM_ENCRYPT=y is required for a guest to run properly as an SEV-SNP
guest, but a guest kernel built with CONFIG_KVM_AMD_SEV=n would get the stub
function of sev_evict_cache() instead of the version that performs the actual
eviction. Move the function declarations under the appropriate #ifdef.

Fixes: 7b306dfa326f ("x86/sev: Evict cache lines during SNP memory validation")
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@kernel.org # 6.16.x
Link: https://lore.kernel.org/r/70e38f2c4a549063de54052c9f64929705313526.1757708959.git.thomas.lendacky@amd.com
[ Move sev_evict_cache() out of shared.c ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/coco/sev/shared.c | 18 ------------------
 arch/x86/include/asm/sev.h | 19 +++++++++++++++++++
 2 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/arch/x86/coco/sev/shared.c b/arch/x86/coco/sev/shared.c
index 16b799f37d6cb..75653edcc5f06 100644
--- a/arch/x86/coco/sev/shared.c
+++ b/arch/x86/coco/sev/shared.c
@@ -1243,24 +1243,6 @@ static void svsm_pval_terminate(struct svsm_pvalidate_call *pc, int ret, u64 svs
 	__pval_terminate(pfn, action, page_size, ret, svsm_ret);
 }
 
-static inline void sev_evict_cache(void *va, int npages)
-{
-	volatile u8 val __always_unused;
-	u8 *bytes = va;
-	int page_idx;
-
-	/*
-	 * For SEV guests, a read from the first/last cache-lines of a 4K page
-	 * using the guest key is sufficient to cause a flush of all cache-lines
-	 * associated with that 4K page without incurring all the overhead of a
-	 * full CLFLUSH sequence.
-	 */
-	for (page_idx = 0; page_idx < npages; page_idx++) {
-		val = bytes[page_idx * PAGE_SIZE];
-		val = bytes[page_idx * PAGE_SIZE + PAGE_SIZE - 1];
-	}
-}
-
 static void svsm_pval_4k_page(unsigned long paddr, bool validate)
 {
 	struct svsm_pvalidate_call *pc;
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ee34ab00a8d6d..a4dae8054fc4b 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -400,6 +400,24 @@ u64 sev_get_status(void);
 void sev_show_status(void);
 void snp_update_svsm_ca(void);
 
+static inline void sev_evict_cache(void *va, int npages)
+{
+	volatile u8 val __always_unused;
+	u8 *bytes = va;
+	int page_idx;
+
+	/*
+	 * For SEV guests, a read from the first/last cache-lines of a 4K page
+	 * using the guest key is sufficient to cause a flush of all cache-lines
+	 * associated with that 4K page without incurring all the overhead of a
+	 * full CLFLUSH sequence.
+	 */
+	for (page_idx = 0; page_idx < npages; page_idx++) {
+		val = bytes[page_idx * PAGE_SIZE];
+		val = bytes[page_idx * PAGE_SIZE + PAGE_SIZE - 1];
+	}
+}
+
 #else	/* !CONFIG_AMD_MEM_ENCRYPT */
 
 #define snp_vmpl 0
@@ -435,6 +453,7 @@ static inline u64 snp_get_unsupported_features(u64 status) { return 0; }
 static inline u64 sev_get_status(void) { return 0; }
 static inline void sev_show_status(void) { }
 static inline void snp_update_svsm_ca(void) { }
+static inline void sev_evict_cache(void *va, int npages) {}
 
 #endif	/* CONFIG_AMD_MEM_ENCRYPT */
 
-- 
2.51.0