linux-kernel - [PATCH] x86/sev: Guard sev_evict_cache() with CONFIG_AMD_MEM

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Message-ID: <70e38f2c4a549063de54052c9f64929705313526.1757708959.git.thomas.lendacky@amd.com>
Date: Fri, 12 Sep 2025 15:29:19 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	Michael Roth <michael.roth@....com>, Sean Christopherson <seanjc@...gle.com>,
	<stable@...nel.org>
Subject: [PATCH] x86/sev: Guard sev_evict_cache() with CONFIG_AMD_MEM_ENCRYPT

The sev_evict_cache() is guest-related code and should be guarded by
CONFIG_AMD_MEM_ENCRYPT, not CONFIG_KVM_AMD_SEV. Move the function
declarations under the appropriate #ifdef.

Fixes: 7b306dfa326f ("x86/sev: Evict cache lines during SNP memory validation")
Cc: <stable@...nel.org>
Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/include/asm/sev.h | 38 +++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 00475b814ac4..e5a7e0ebdc73 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -579,6 +579,24 @@ struct psc_desc {
 	u64 caa_pa;
 };
 
+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
@@ -624,6 +642,7 @@ static inline enum es_result savic_register_gpa(u64 gpa) { return ES_UNSUPPORTED
 static inline enum es_result savic_unregister_gpa(u64 *gpa) { return ES_UNSUPPORTED; }
 static inline void savic_ghcb_msr_write(u32 reg, u64 value) { }
 static inline u64 savic_ghcb_msr_read(u32 reg) { return 0; }
+static inline void sev_evict_cache(void *va, int npages) {}
 
 #endif	/* CONFIG_AMD_MEM_ENCRYPT */
 
@@ -638,24 +657,6 @@ int rmp_make_shared(u64 pfn, enum pg_level level);
 void snp_leak_pages(u64 pfn, unsigned int npages);
 void kdump_sev_callback(void);
 void snp_fixup_e820_tables(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
 static inline bool snp_probe_rmptable_info(void) { return false; }
 static inline int snp_rmptable_init(void) { return -ENOSYS; }
@@ -671,7 +672,6 @@ static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV
 static inline void snp_leak_pages(u64 pfn, unsigned int npages) {}
 static inline void kdump_sev_callback(void) { }
 static inline void snp_fixup_e820_tables(void) {}
-static inline void sev_evict_cache(void *va, int npages) {}
 #endif
 
 #endif

base-commit: fc1ded58808520a1ced0c4e2e5fb0dbd33b33612
-- 
2.46.2