linux-kernel - [PATCH 1/3] KVM: x86: Introduce supported_quirks for platform-specific valid quirks

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Message-ID: <20250224070832.31394-1-yan.y.zhao@intel.com>
Date: Mon, 24 Feb 2025 15:08:32 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: pbonzini@...hat.com,
	seanjc@...gle.com
Cc: rick.p.edgecombe@...el.com,
	kevin.tian@...el.com,
	linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	Yan Zhao <yan.y.zhao@...el.com>
Subject: [PATCH 1/3] KVM: x86: Introduce supported_quirks for platform-specific valid quirks

Introduce supported_quirks in kvm_caps to store platform-specific valid
quirks.

Rename KVM_X86_VALID_QUIRKS to KVM_X86_VALID_QUIRKS_COMMON, representing
valid quirks common to all x86 platforms. Initialize
kvm_caps.supported_quirks to KVM_X86_VALID_QUIRKS_COMMON in the common
vendor initializer kvm_x86_vendor_init().

Use kvm_caps.supported_quirks to respond to user queries about valid quirks
and to mask out unsupported quirks provided by the user.

In kvm_check_has_quirk(), in additional to check if a quirk is not
explicitly disabled by the user, also verify if the quirk is supported by
the platform. This ensures KVM does not treat a quirk as enabled if it's
not explicitly disabled by the user but is outside the platform supported
mask.

This is a preparation for introducing quirks specific to certain platforms,
e.g., quirks present only on Intel platforms and not on AMD.

No functional changes intended.

Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
---
 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/x86.c              |  5 +++--
 arch/x86/kvm/x86.h              | 12 +++++++-----
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 089cf2c82414..8d15e604613b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2409,7 +2409,7 @@ int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages);
 #define KVM_CLOCK_VALID_FLAGS						\
 	(KVM_CLOCK_TSC_STABLE | KVM_CLOCK_REALTIME | KVM_CLOCK_HOST_TSC)
 
-#define KVM_X86_VALID_QUIRKS			\
+#define KVM_X86_VALID_QUIRKS_COMMON		\
 	(KVM_X86_QUIRK_LINT0_REENABLED |	\
 	 KVM_X86_QUIRK_CD_NW_CLEARED |		\
 	 KVM_X86_QUIRK_LAPIC_MMIO_HOLE |	\
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3078e09fc841..4f1b73620c6a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4782,7 +4782,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = enable_pmu ? KVM_CAP_PMU_VALID_MASK : 0;
 		break;
 	case KVM_CAP_DISABLE_QUIRKS2:
-		r = KVM_X86_VALID_QUIRKS;
+		r = kvm_caps.supported_quirks;
 		break;
 	case KVM_CAP_X86_NOTIFY_VMEXIT:
 		r = kvm_caps.has_notify_vmexit;
@@ -6521,7 +6521,7 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 	switch (cap->cap) {
 	case KVM_CAP_DISABLE_QUIRKS2:
 		r = -EINVAL;
-		if (cap->args[0] & ~KVM_X86_VALID_QUIRKS)
+		if (cap->args[0] & ~kvm_caps.supported_quirks)
 			break;
 		fallthrough;
 	case KVM_CAP_DISABLE_QUIRKS:
@@ -9775,6 +9775,7 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
 		kvm_host.xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
 		kvm_caps.supported_xcr0 = kvm_host.xcr0 & KVM_SUPPORTED_XCR0;
 	}
+	kvm_caps.supported_quirks = KVM_X86_VALID_QUIRKS_COMMON;
 
 	rdmsrl_safe(MSR_EFER, &kvm_host.efer);
 
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 8ce6da98b5a2..772d5c320be1 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -34,6 +34,7 @@ struct kvm_caps {
 	u64 supported_xcr0;
 	u64 supported_xss;
 	u64 supported_perf_cap;
+	u64 supported_quirks;
 };
 
 struct kvm_host_values {
@@ -354,11 +355,6 @@ static inline void kvm_register_write(struct kvm_vcpu *vcpu,
 	return kvm_register_write_raw(vcpu, reg, val);
 }
 
-static inline bool kvm_check_has_quirk(struct kvm *kvm, u64 quirk)
-{
-	return !(kvm->arch.disabled_quirks & quirk);
-}
-
 void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip);
 
 u64 get_kvmclock_ns(struct kvm *kvm);
@@ -394,6 +390,12 @@ extern struct kvm_host_values kvm_host;
 
 extern bool enable_pmu;
 
+static inline bool kvm_check_has_quirk(struct kvm *kvm, u64 quirk)
+{
+	return (kvm_caps.supported_quirks & quirk) &&
+	       !(kvm->arch.disabled_quirks & quirk);
+}
+
 /*
  * Get a filtered version of KVM's supported XCR0 that strips out dynamic
  * features for which the current process doesn't (yet) have permission to use.
-- 
2.43.2