The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 7f830e126dc357fc086905ce9730140fd4528d66 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025092126-fabulous-despair-ac21@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7f830e126dc357fc086905ce9730140fd4528d66 Mon Sep 17 00:00:00 2001 From: Tom Lendacky thomas.lendacky@amd.com Date: Mon, 15 Sep 2025 11:04:12 -0500 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.

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/70e38f2c4a549063de54052c9f64929705313526.175770895...

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index 02236962fdb1..465b19fd1a2d 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -562,6 +562,24 @@ enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,

extern struct ghcb *boot_ghcb;

+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 @@ -605,6 +623,7 @@ static inline int snp_send_guest_request(struct snp_msg_desc *mdesc, static inline int snp_svsm_vtpm_send_command(u8 *buffer) { return -ENODEV; } static inline void __init snp_secure_tsc_prepare(void) { } static inline void __init snp_secure_tsc_init(void) { } +static inline void sev_evict_cache(void *va, int npages) {}

#endif /* CONFIG_AMD_MEM_ENCRYPT */

@@ -619,24 +638,6 @@ 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; } @@ -652,7 +653,6 @@ 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