linux-kernel - [PATCH 1/3] kvm: wire up KVM_CAP_VM_GPA

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Date: Fri,  1 Mar 2024 11:14:07 +0100
From: Gerd Hoffmann <kraxel@...hat.com>
To: kvm@...r.kernel.org
Cc: Gerd Hoffmann <kraxel@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	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 (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
	"H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND 64-BIT))
Subject: [PATCH 1/3] kvm: wire up KVM_CAP_VM_GPA_BITS for x86

Add new guest_phys_bits field to kvm_caps, return the value to
userspace when asked for KVM_CAP_VM_GPA_BITS capability.

Initialize guest_phys_bits with boot_cpu_data.x86_phys_bits.
Vendor modules (i.e. vmx and svm) can adjust this field in case
additional restrictions apply, for example in case EPT has no
support for 5-level paging.

Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
---
 arch/x86/kvm/x86.h | 2 ++
 arch/x86/kvm/x86.c | 5 +++++
 2 files changed, 7 insertions(+)

diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 2f7e19166658..e03aec3527f8 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -24,6 +24,8 @@ struct kvm_caps {
 	bool has_bus_lock_exit;
 	/* notify VM exit supported? */
 	bool has_notify_vmexit;
+	/* usable guest phys bits */
+	u32  guest_phys_bits;
 
 	u64 supported_mce_cap;
 	u64 supported_xcr0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 48a61d283406..e270b9b708d1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4784,6 +4784,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		if (kvm_is_vm_type_supported(KVM_X86_SW_PROTECTED_VM))
 			r |= BIT(KVM_X86_SW_PROTECTED_VM);
 		break;
+	case KVM_CAP_VM_GPA_BITS:
+		r = kvm_caps.guest_phys_bits;
+		break;
 	default:
 		break;
 	}
@@ -9706,6 +9709,8 @@ static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
 	if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
 		rdmsrl(MSR_IA32_ARCH_CAPABILITIES, host_arch_capabilities);
 
+	kvm_caps.guest_phys_bits = boot_cpu_data.x86_phys_bits;
+
 	r = ops->hardware_setup();
 	if (r != 0)
 		goto out_mmu_exit;
-- 
2.44.0