[v3,38/75] x86/sev-es: Add SEV-ES Feature Detection

Commit Message

Joerg Roedel April 28, 2020, 3:16 p.m. UTC

From: Joerg Roedel <[e-mail]>

Add the sev_es_active function for checking whether SEV-ES is enabled.
Also cache the value of MSR_AMD64_SEV at boot to speed up the feature
checking in the running code.

Signed-off-by: Joerg Roedel <[e-mail]>
---
 arch/x86/include/asm/mem_encrypt.h |  3 +++
 arch/x86/include/asm/msr-index.h   |  2 ++
 arch/x86/mm/mem_encrypt.c          | 10 +++++++++-
 arch/x86/mm/mem_encrypt_identity.c |  3 +++
 4 files changed, 17 insertions(+), 1 deletion(-)

Comments

Borislav Petkov May 20, 2020, 8:39 a.m. UTC | #1

On Tue, Apr 28, 2020 at 05:16:48PM +0200, Joerg Roedel wrote:
> +bool sev_es_active(void)
> +{
> +	return !!(sev_status & MSR_AMD64_SEV_ES_ENABLED);
> +}
> +EXPORT_SYMBOL_GPL(sev_es_active);

I don't see this being used in modules anywhere in the patchset. Or am I
missing something?

Joerg Roedel June 3, 2020, 3:24 p.m. UTC | #2

On Wed, May 20, 2020 at 10:39:16AM +0200, Borislav Petkov wrote:
> On Tue, Apr 28, 2020 at 05:16:48PM +0200, Joerg Roedel wrote:
> > +bool sev_es_active(void)
> > +{
> > +	return !!(sev_status & MSR_AMD64_SEV_ES_ENABLED);
> > +}
> > +EXPORT_SYMBOL_GPL(sev_es_active);
> 
> I don't see this being used in modules anywhere in the patchset. Or am I
> missing something?

It is used in several places, for example do do_nmi() to conditionally
re-open the NMI window in SEV-ES guests. But there are other uses too,
like int sev_es_efi_map_ghcbs() or in sev_es_init_vc_handling() to opt
out if not running as an SEV-ES guest.


	Joerg

Patch

diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
index 848ce43b9040..6f61bb93366a 100644
--- a/arch/x86/include/asm/mem_encrypt.h
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -19,6 +19,7 @@ 
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 
 extern u64 sme_me_mask;
+extern u64 sev_status;
 extern bool sev_enabled;
 
 void sme_encrypt_execute(unsigned long encrypted_kernel_vaddr,
@@ -49,6 +50,7 @@  void __init mem_encrypt_free_decrypted_mem(void);
 
 bool sme_active(void);
 bool sev_active(void);
+bool sev_es_active(void);
 
 #define __bss_decrypted __attribute__((__section__(".bss..decrypted")))
 
@@ -71,6 +73,7 @@  static inline void __init sme_enable(struct boot_params *bp) { }
 
 static inline bool sme_active(void) { return false; }
 static inline bool sev_active(void) { return false; }
+static inline bool sev_es_active(void) { return false; }
 
 static inline int __init
 early_set_memory_decrypted(unsigned long vaddr, unsigned long size) { return 0; }
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 198aa06778ce..22b35e15b8e0 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -444,7 +444,9 @@ 
 #define MSR_AMD64_SEV_ES_GHCB		0xc0010130
 #define MSR_AMD64_SEV			0xc0010131
 #define MSR_AMD64_SEV_ENABLED_BIT	0
+#define MSR_AMD64_SEV_ES_ENABLED_BIT	1
 #define MSR_AMD64_SEV_ENABLED		BIT_ULL(MSR_AMD64_SEV_ENABLED_BIT)
+#define MSR_AMD64_SEV_ES_ENABLED	BIT_ULL(MSR_AMD64_SEV_ES_ENABLED_BIT)
 
 #define MSR_AMD64_VIRT_SPEC_CTRL	0xc001011f
 
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index a03614bd3e1a..3e59fcd7f9ac 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -38,6 +38,7 @@ 
  * section is later cleared.
  */
 u64 sme_me_mask __section(.data) = 0;
+u64 sev_status __section(.data) = 0;
 EXPORT_SYMBOL(sme_me_mask);
 DEFINE_STATIC_KEY_FALSE(sev_enable_key);
 EXPORT_SYMBOL_GPL(sev_enable_key);
@@ -347,9 +348,16 @@  bool sme_active(void)
 
 bool sev_active(void)
 {
-	return sme_me_mask && sev_enabled;
+	return !!(sev_status & MSR_AMD64_SEV_ENABLED);
 }
 
+bool sev_es_active(void)
+{
+	return !!(sev_status & MSR_AMD64_SEV_ES_ENABLED);
+}
+EXPORT_SYMBOL_GPL(sev_es_active);
+
+
 /* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
 bool force_dma_unencrypted(struct device *dev)
 {
diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
index e2b0e2ac07bb..68d75379e06a 100644
--- a/arch/x86/mm/mem_encrypt_identity.c
+++ b/arch/x86/mm/mem_encrypt_identity.c
@@ -540,6 +540,9 @@  void __init sme_enable(struct boot_params *bp)
 		if (!(msr & MSR_AMD64_SEV_ENABLED))
 			return;
 
+		/* Save SEV_STATUS to avoid reading MSR again */
+		sev_status = msr;
+
 		/* SEV state cannot be controlled by a command line option */
 		sme_me_mask = me_mask;
 		sev_enabled = true;