linux-kernel - Re: [PATCH v2 06/12] x86/sev: Replace occurrences of sev_active() with prot_guest

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Message-ID: <YRuJPqxFZ6ItZd++@zn.tnic>
Date:   Tue, 17 Aug 2021 12:02:38 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        iommu@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-graphics-maintainer@...are.com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        kexec@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        Brijesh Singh <brijesh.singh@....com>,
        Joerg Roedel <joro@...tes.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH v2 06/12] x86/sev: Replace occurrences of sev_active()
 with prot_guest_has()

On Fri, Aug 13, 2021 at 11:59:25AM -0500, Tom Lendacky wrote:
> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> index 8e7b517ad738..66ff788b79c9 100644
> --- a/arch/x86/kernel/machine_kexec_64.c
> +++ b/arch/x86/kernel/machine_kexec_64.c
> @@ -167,7 +167,7 @@ static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
>  	}
>  	pte = pte_offset_kernel(pmd, vaddr);
>  
> -	if (sev_active())
> +	if (prot_guest_has(PATTR_GUEST_MEM_ENCRYPT))
>  		prot = PAGE_KERNEL_EXEC;
>  
>  	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, prot));
> @@ -207,7 +207,7 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
>  	level4p = (pgd_t *)__va(start_pgtable);
>  	clear_page(level4p);
>  
> -	if (sev_active()) {
> +	if (prot_guest_has(PATTR_GUEST_MEM_ENCRYPT)) {
>  		info.page_flag   |= _PAGE_ENC;
>  		info.kernpg_flag |= _PAGE_ENC;
>  	}
> @@ -570,12 +570,12 @@ void arch_kexec_unprotect_crashkres(void)
>   */
>  int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, gfp_t gfp)
>  {
> -	if (sev_active())
> +	if (!prot_guest_has(PATTR_HOST_MEM_ENCRYPT))
>  		return 0;
>  
>  	/*
> -	 * If SME is active we need to be sure that kexec pages are
> -	 * not encrypted because when we boot to the new kernel the
> +	 * If host memory encryption is active we need to be sure that kexec
> +	 * pages are not encrypted because when we boot to the new kernel the
>  	 * pages won't be accessed encrypted (initially).
>  	 */

That hunk belongs logically into the previous patch which removes
sme_active().

>  	return set_memory_decrypted((unsigned long)vaddr, pages);
> @@ -583,12 +583,12 @@ int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, gfp_t gfp)
>  
>  void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages)
>  {
> -	if (sev_active())
> +	if (!prot_guest_has(PATTR_HOST_MEM_ENCRYPT))
>  		return;
>  
>  	/*
> -	 * If SME is active we need to reset the pages back to being
> -	 * an encrypted mapping before freeing them.
> +	 * If host memory encryption is active we need to reset the pages back
> +	 * to being an encrypted mapping before freeing them.
>  	 */
>  	set_memory_encrypted((unsigned long)vaddr, pages);
>  }
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index e8ccab50ebf6..b69f5ac622d5 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -25,6 +25,7 @@
>  #include <linux/pagemap.h>
>  #include <linux/swap.h>
>  #include <linux/rwsem.h>
> +#include <linux/protected_guest.h>
>  
>  #include <asm/apic.h>
>  #include <asm/perf_event.h>
> @@ -457,7 +458,7 @@ static int has_svm(void)
>  		return 0;
>  	}
>  
> -	if (sev_active()) {
> +	if (prot_guest_has(PATTR_SEV)) {
>  		pr_info("KVM is unsupported when running as an SEV guest\n");
>  		return 0;

Same question as for PATTR_SME. PATTR_GUEST_MEM_ENCRYPT should be enough.

> @@ -373,7 +373,7 @@ int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size)
>   * up under SME the trampoline area cannot be encrypted, whereas under SEV
>   * the trampoline area must be encrypted.
>   */
> -bool sev_active(void)
> +static bool sev_active(void)
>  {
>  	return sev_status & MSR_AMD64_SEV_ENABLED;
>  }
> @@ -382,7 +382,6 @@ static bool sme_active(void)
>  {
>  	return sme_me_mask && !sev_active();
>  }
> -EXPORT_SYMBOL_GPL(sev_active);

Just get rid of it altogether.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette