[PATCH] x86/sev: mem_encrypt_free_decrypted_mem(): encrypt the pages for AMD SME only

[PATCH] x86/sev: mem_encrypt_free_decrypted_mem(): encrypt the pages for AMD SME only

[Dexuan Cui]

sme_postprocess_startup() marks the __start_bss_decrypted pages shared
for AMD SME only, so here set_memory_encrypted() should be called for AMD
SME only, i.e. don't call the set_memory_encrypted() for TDX, otherwise the
error "failed to free unused decrypted pages" appears in 'dmesg'.

Fixes: b3f0907c71e0 ("x86/mm: Add .bss..decrypted section to hold shared variables")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
---
 arch/x86/mm/mem_encrypt_amd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
index 9c4d8dbcb129..fd9b58402a22 100644
--- a/arch/x86/mm/mem_encrypt_amd.c
+++ b/arch/x86/mm/mem_encrypt_amd.c
@@ -516,7 +516,7 @@ void __init mem_encrypt_free_decrypted_mem(void)
 	 * The unused memory range was mapped decrypted, change the encryption
 	 * attribute from decrypted to encrypted before freeing it.
 	 */
-	if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
+	if (sme_me_mask && cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
 		r = set_memory_encrypted(vaddr, npages);
 		if (r) {
 			pr_warn("failed to free unused decrypted pages\n");
-- 
2.25.1

RE: [PATCH] x86/sev: mem_encrypt_free_decrypted_mem(): encrypt the pages for AMD SME only

[Dexuan Cui]

> From: Dexuan Cui <decui@microsoft.com>
> Sent: Sunday, November 27, 2022 5:29 PM
> To: dave.hansen@linux.intel.com; luto@kernel.org; peterz@infradead.org;
> tglx@linutronix.de; mingo@redhat.com; bp@alien8.de; x86@kernel.org;
> hpa@zytor.com; brijesh.singh@amd.com
> Cc: linux-kernel@vger.kernel.org; linux-hyperv@vger.kernel.org; Dexuan Cui
> <decui@microsoft.com>
> Subject: [PATCH] x86/sev: mem_encrypt_free_decrypted_mem(): encrypt the
> pages for AMD SME only
> 
> sme_postprocess_startup() marks the __start_bss_decrypted pages shared
> for AMD SME only, so here set_memory_encrypted() should be called for AMD
> SME only, i.e. don't call the set_memory_encrypted() for TDX, otherwise the
> error "failed to free unused decrypted pages" appears in 'dmesg'.
> 
> Fixes: b3f0907c71e0 ("x86/mm: Add .bss..decrypted section to hold shared
> variables")
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> ---
>  arch/x86/mm/mem_encrypt_amd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/mem_encrypt_amd.c
> b/arch/x86/mm/mem_encrypt_amd.c
> index 9c4d8dbcb129..fd9b58402a22 100644
> --- a/arch/x86/mm/mem_encrypt_amd.c
> +++ b/arch/x86/mm/mem_encrypt_amd.c
> @@ -516,7 +516,7 @@ void __init mem_encrypt_free_decrypted_mem(void)
>  	 * The unused memory range was mapped decrypted, change the
> encryption
>  	 * attribute from decrypted to encrypted before freeing it.
>  	 */
> -	if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
> +	if (sme_me_mask && cc_platform_has(CC_ATTR_MEM_ENCRYPT)) {
>  		r = set_memory_encrypted(vaddr, npages);
>  		if (r) {
>  			pr_warn("failed to free unused decrypted pages\n");
> --

Please ignore this patch as Michael posted a similar patch earlier:
https://lwn.net/ml/linux-kernel/1668624097-14884-6-git-send-email-mikelley%40microsoft.com/