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

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Message-ID: <b346ae1b-dbd3-cdbd-b5cd-b5ab9c304737@amd.com>
Date:   Tue, 17 Aug 2021 10:26:18 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Borislav Petkov <bp@...en8.de>
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 8/17/21 5:02 AM, Borislav Petkov wrote:
> 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().

I was trying to keep the sev_active() changes separate... so even though
it's an SME thing, I kept it here. But I can move it to the previous
patch, it just might look strange.

> 
>>  	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.

Yup, I'll change them all.

> 
>> @@ -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.

Ok.

Thanks,
Tom

> 
> Thx.
>