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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id n13sm1745261ejx.27.2021.04.22.05.05.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Apr 2021 05:05:47 -0700 (PDT) Subject: Re: [PATCH v5 06/15] x86/sev: Drop redundant and potentially misleading 'sev_enabled' To: Sean Christopherson , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Borislav Petkov Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Tom Lendacky , Brijesh Singh References: <20210422021125.3417167-1-seanjc@google.com> <20210422021125.3417167-7-seanjc@google.com> From: Paolo Bonzini Message-ID: <8f1fa7e0-b940-6d1d-1a74-11014901fc0d@redhat.com> Date: Thu, 22 Apr 2021 14:05:46 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210422021125.3417167-7-seanjc@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/04/21 04:11, Sean Christopherson wrote: > Drop the sev_enabled flag and switch its one user over to sev_active(). > sev_enabled was made redundant with the introduction of sev_status in > commit b57de6cd1639 ("x86/sev-es: Add SEV-ES Feature Detection"). > sev_enabled and sev_active() are guaranteed to be equivalent, as each is > true iff 'sev_status & MSR_AMD64_SEV_ENABLED' is true, and are only ever > written in tandem (ignoring compressed boot's version of sev_status). > > Removing sev_enabled avoids confusion over whether it refers to the guest > or the host, and will also allow KVM to usurp "sev_enabled" for its own > purposes. > > No functional change intended. > > Reviewed-by: Tom Lendacky > Reviewed-by: Brijesh Singh > Signed-off-by: Sean Christopherson Boris or another x86 maintainer, can you ack this small patch? We would like to use sev_enabled as a static variable in KVM. Paolo > --- > arch/x86/include/asm/mem_encrypt.h | 1 - > arch/x86/mm/mem_encrypt.c | 12 +++++------- > arch/x86/mm/mem_encrypt_identity.c | 1 - > 3 files changed, 5 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h > index 31c4df123aa0..9c80c68d75b5 100644 > --- a/arch/x86/include/asm/mem_encrypt.h > +++ b/arch/x86/include/asm/mem_encrypt.h > @@ -20,7 +20,6 @@ > > extern u64 sme_me_mask; > extern u64 sev_status; > -extern bool sev_enabled; > > void sme_encrypt_execute(unsigned long encrypted_kernel_vaddr, > unsigned long decrypted_kernel_vaddr, > diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c > index 4b01f7dbaf30..be384d8d0543 100644 > --- a/arch/x86/mm/mem_encrypt.c > +++ b/arch/x86/mm/mem_encrypt.c > @@ -44,8 +44,6 @@ EXPORT_SYMBOL(sme_me_mask); > DEFINE_STATIC_KEY_FALSE(sev_enable_key); > EXPORT_SYMBOL_GPL(sev_enable_key); > > -bool sev_enabled __section(".data"); > - > /* Buffer used for early in-place encryption by BSP, no locking needed */ > static char sme_early_buffer[PAGE_SIZE] __initdata __aligned(PAGE_SIZE); > > @@ -373,15 +371,15 @@ 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 sme_active(void) > -{ > - return sme_me_mask && !sev_enabled; > -} > - > bool sev_active(void) > { > return sev_status & MSR_AMD64_SEV_ENABLED; > } > + > +bool sme_active(void) > +{ > + return sme_me_mask && !sev_active(); > +} > EXPORT_SYMBOL_GPL(sev_active); > > /* Needs to be called from non-instrumentable code */ > diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c > index 6c5eb6f3f14f..0c2759b7f03a 100644 > --- a/arch/x86/mm/mem_encrypt_identity.c > +++ b/arch/x86/mm/mem_encrypt_identity.c > @@ -545,7 +545,6 @@ void __init sme_enable(struct boot_params *bp) > > /* SEV state cannot be controlled by a command line option */ > sme_me_mask = me_mask; > - sev_enabled = true; > physical_mask &= ~sme_me_mask; > return; > } >