linux-kernel - [PATCH RFC v7 02/64] KVM: x86: Add KVM_CAP_UNMAPPED_PRIVATE

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Date:   Wed, 14 Dec 2022 13:39:54 -0600
From:   Michael Roth <michael.roth@....com>
To:     <kvm@...r.kernel.org>
CC:     <linux-coco@...ts.linux.dev>, <linux-mm@...ck.org>,
        <linux-crypto@...r.kernel.org>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <jroedel@...e.de>, <thomas.lendacky@....com>,
        <hpa@...or.com>, <ardb@...nel.org>, <pbonzini@...hat.com>,
        <seanjc@...gle.com>, <vkuznets@...hat.com>,
        <wanpengli@...cent.com>, <jmattson@...gle.com>, <luto@...nel.org>,
        <dave.hansen@...ux.intel.com>, <slp@...hat.com>,
        <pgonda@...gle.com>, <peterz@...radead.org>,
        <srinivas.pandruvada@...ux.intel.com>, <rientjes@...gle.com>,
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        <alpergun@...gle.com>, <dgilbert@...hat.com>, <jarkko@...nel.org>,
        <ashish.kalra@....com>, <harald@...fian.com>
Subject: [PATCH RFC v7 02/64] KVM: x86: Add KVM_CAP_UNMAPPED_PRIVATE_MEMORY

This mainly indicates to KVM that it should expect all private guest
memory to be backed by private memslots. Ideally this would work
similarly for others archs, give or take a few additional flags, but
for now it's a simple boolean indicator for x86.

Signed-off-by: Michael Roth <michael.roth@....com>
---
 arch/x86/include/asm/kvm_host.h |  3 +++
 arch/x86/kvm/x86.c              | 10 ++++++++++
 include/uapi/linux/kvm.h        |  1 +
 3 files changed, 14 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 27ef31133352..2b6244525107 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1438,6 +1438,9 @@ struct kvm_arch {
 	 */
 #define SPLIT_DESC_CACHE_MIN_NR_OBJECTS (SPTE_ENT_PER_PAGE + 1)
 	struct kvm_mmu_memory_cache split_desc_cache;
+
+	/* Use/enforce unmapped private memory. */
+	bool upm_mode;
 };
 
 struct kvm_vm_stat {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c67e22f3e2ee..99ecf99bc4d2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4421,6 +4421,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_EXIT_HYPERCALL:
 		r = KVM_EXIT_HYPERCALL_VALID_MASK;
 		break;
+#ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES
+	case KVM_CAP_UNMAPPED_PRIVATE_MEM:
+		r = 1;
+		break;
+#endif
 	case KVM_CAP_SET_GUEST_DEBUG2:
 		return KVM_GUESTDBG_VALID_MASK;
 #ifdef CONFIG_KVM_XEN
@@ -6382,6 +6387,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 		}
 		mutex_unlock(&kvm->lock);
 		break;
+	case KVM_CAP_UNMAPPED_PRIVATE_MEM:
+		kvm->arch.upm_mode = true;
+		r = 0;
+		break;
 	default:
 		r = -EINVAL;
 		break;
@@ -12128,6 +12137,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	kvm->arch.default_tsc_khz = max_tsc_khz ? : tsc_khz;
 	kvm->arch.guest_can_read_msr_platform_info = true;
 	kvm->arch.enable_pmu = enable_pmu;
+	kvm->arch.upm_mode = false;
 
 #if IS_ENABLED(CONFIG_HYPERV)
 	spin_lock_init(&kvm->arch.hv_root_tdp_lock);
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index c7e9d375a902..cc9424ccf9b2 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1219,6 +1219,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_DIRTY_LOG_RING_ACQ_REL 223
 #define KVM_CAP_S390_PROTECTED_ASYNC_DISABLE 224
 #define KVM_CAP_MEMORY_ATTRIBUTES 225
+#define KVM_CAP_UNMAPPED_PRIVATE_MEM 240
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.25.1