Re: [PATCH v5 06/15] x86/sev: Drop redundant and potentially misleading 'sev_enabled'

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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 <thomas.lendacky@xxxxxxx>
Reviewed-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

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;
  	}





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