linux-kernel - [PATCH v2 2/2] KVM: SVM: enhance info printk's in SEV init

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Message-Id: <20230522161249.800829-3-aleksandr.mikhalitsyn@canonical.com>
Date:   Mon, 22 May 2023 18:12:48 +0200
From:   Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
To:     pbonzini@...hat.com
Cc:     Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Stéphane Graber <stgraber@...ntu.com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH v2 2/2] KVM: SVM: enhance info printk's in SEV init

Let's print available ASID ranges for SEV/SEV-ES guests.
This information can be useful for system administrator
to debug if SEV/SEV-ES fails to enable.

There are a few reasons.
SEV:
- NPT is disabled (module parameter)
- CPU lacks some features (sev, decodeassists)
- Maximum SEV ASID is 0

SEV-ES:
- mmio_caching is disabled (module parameter)
- CPU lacks sev_es feature
- Minimum SEV ASID value is 1 (can be adjusted in BIOS/UEFI)

Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Stéphane Graber <stgraber@...ntu.com>
Cc: kvm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
---
v2:
	- print only the ASID ranges according to Sean's suggestion
---
 arch/x86/kvm/svm/sev.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index cc832a8d1bca..fff63d1f2a34 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2224,7 +2224,6 @@ void __init sev_hardware_setup(void)
 		goto out;
 	}
 
-	pr_info("SEV supported: %u ASIDs\n", sev_asid_count);
 	sev_supported = true;
 
 	/* SEV-ES support requested? */
@@ -2252,10 +2251,16 @@ void __init sev_hardware_setup(void)
 	if (misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count))
 		goto out;
 
-	pr_info("SEV-ES supported: %u ASIDs\n", sev_es_asid_count);
 	sev_es_supported = true;
 
 out:
+	if (boot_cpu_has(X86_FEATURE_SEV))
+		pr_info("SEV %s (ASIDs %u - %u)\n",
+			sev_supported ? "enabled" : "disabled", min_sev_asid, max_sev_asid);
+	if (boot_cpu_has(X86_FEATURE_SEV_ES))
+		pr_info("SEV-ES %s (ASIDs %u - %u)\n",
+			sev_es_supported ? "enabled" : "disabled", 1, min_sev_asid - 1);
+
 	sev_enabled = sev_supported;
 	sev_es_enabled = sev_es_supported;
 #endif
-- 
2.34.1