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

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Message-ID: <SA1PR21MB13356CD7D2AADCD3F6D8B49EBF139@SA1PR21MB1335.namprd21.prod.outlook.com>
Date:   Mon, 28 Nov 2022 02:38:52 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "luto@...nel.org" <luto@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "brijesh.singh@....com" <brijesh.singh@....com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>
Subject: RE: [PATCH] x86/sev: mem_encrypt_free_decrypted_mem(): encrypt the
 pages for AMD SME only

> From: Dexuan Cui <decui@...rosoft.com>
> Sent: Sunday, November 27, 2022 5:29 PM
> To: dave.hansen@...ux.intel.com; luto@...nel.org; peterz@...radead.org;
> tglx@...utronix.de; mingo@...hat.com; bp@...en8.de; x86@...nel.org;
> hpa@...or.com; brijesh.singh@....com
> Cc: linux-kernel@...r.kernel.org; linux-hyperv@...r.kernel.org; Dexuan Cui
> <decui@...rosoft.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@...rosoft.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/