Kernel KVM virtualization development
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From: Sriram Nambakam <snambakam@linux.microsoft.com>
To: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Subject: [RFC PATCH v2 1/8] KVM: x86: raise the default maximum planes to two
Date: Mon, 10 Aug 2026 18:52:36 -0700	[thread overview]
Message-ID: <20260811015243.188486-2-snambakam@linux.microsoft.com> (raw)
In-Reply-To: <20260811015243.188486-1-snambakam@linux.microsoft.com>

The default max-planes callback returns 1, which limits KVM_CAP_PLANES to a
single plane on VMX (and on SVM for non-SEV-SNP guests).  VBS needs a normal
plane (0) and one secure plane (1), so return 2 by default.  This is still
gated by irqchip=split in kvm_arch_max_planes().
---
 arch/x86/kvm/x86.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 35fbe0776a3e..29766c19c289 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -478,7 +478,8 @@ static unsigned int num_msr_based_features;
 
 unsigned kvm_x86_default_max_planes(struct kvm *kvm)
 {
-	return 1;
+	/* Support a normal plane (0) and one secure plane (1) for VBS. */
+	return 2;
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_x86_default_max_planes);
 
-- 
2.55.0


  reply	other threads:[~2026-08-11  1:53 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-11  1:52 [RFC PATCH v2 0/8] VBS/VSM-on-KVM: guest support using VM Planes Sriram Nambakam
2026-08-11  1:52 ` Sriram Nambakam [this message]
2026-08-11  1:52 ` [RFC PATCH v2 2/8] security/vbs: introduce core VBS framework Sriram Nambakam
2026-08-11  1:52 ` [RFC PATCH v2 3/8] security/vbs: add platform probe and backend registration Sriram Nambakam
2026-08-11  1:52 ` [RFC PATCH v2 4/8] security/vbs: add KVM software planes backend Sriram Nambakam
2026-08-11  1:52 ` [RFC PATCH v2 5/8] security/vbs: enable the backend after driver init Sriram Nambakam
2026-08-11  1:52 ` [RFC PATCH v2 6/8] vm_planes: add hypervisor-assisted plane bootstrap Sriram Nambakam
2026-08-11  1:52 ` [RFC PATCH v2 7/8] security/vbs: bootstrap the plane from the enable path Sriram Nambakam
2026-08-11  1:52 ` [RFC PATCH v2 8/8] drivers/virt: add KVM VM-planes secure-plane monitor Sriram Nambakam

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