[PATCH v2 0/2] KVM: SVM: Add support for 4096 vcpus with x2AVIC

[PATCH v2 0/2] KVM: SVM: Add support for 4096 vcpus with x2AVIC

[Naveen N Rao (AMD)]

Patch 1 adds support for up to 4096 vcpus with x2AVIC, and is unchanged 
since v1:
http://lkml.kernel.org/r/20241008171156.11972-1-suravee.suthikulpanit@amd.com

Patch 2 is new and limits the value that is programmed into 
AVIC_PHYSICAL_MAX_INDEX in the VMCB based on the max APIC ID indicated 
by the VMM.


- Naveen


Naveen N Rao (AMD) (1):
  KVM: SVM: Limit AVIC physical max index based on configured
    max_vcpu_ids

Suravee Suthikulpanit (1):
  KVM: SVM: Increase X2AVIC limit to 4096 vcpus

 arch/x86/include/asm/svm.h |  4 ++
 arch/x86/kvm/svm/avic.c    | 82 ++++++++++++++++++++++++++++----------
 arch/x86/kvm/svm/svm.c     |  6 +++
 arch/x86/kvm/svm/svm.h     |  1 +
 4 files changed, 73 insertions(+), 20 deletions(-)


base-commit: eb723766b1030a23c38adf2348b7c3d1409d11f0
-- 
2.48.1

[PATCH v2 1/2] KVM: SVM: Increase X2AVIC limit to 4096 vcpus

[Naveen N Rao (AMD)]

From: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>

Newer AMD platforms enhance x2AVIC feature to support up to 4096 vcpus.
This capatility is detected via CPUID_Fn8000000A_ECX[x2AVIC_EXT].

Modify the SVM driver to check the capability. If detected, extend bitmask
for guest max physical APIC ID to 0xFFF, increase maximum vcpu index to
4095, and increase the size of the Phyical APIC ID table from 4K to 32K in
order to accommodate up to 4096 entries.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
 arch/x86/include/asm/svm.h |  4 ++++
 arch/x86/kvm/svm/avic.c    | 42 ++++++++++++++++++++++++++------------
 2 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index 2b59b9951c90..2e9728cec242 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -268,6 +268,7 @@ enum avic_ipi_failure_cause {
 };
 
 #define AVIC_PHYSICAL_MAX_INDEX_MASK	GENMASK_ULL(8, 0)
+#define AVIC_PHYSICAL_MAX_INDEX_4K_MASK	GENMASK_ULL(11, 0)
 
 /*
  * For AVIC, the max index allowed for physical APIC ID table is 0xfe (254), as
@@ -277,11 +278,14 @@ enum avic_ipi_failure_cause {
 
 /*
  * For x2AVIC, the max index allowed for physical APIC ID table is 0x1ff (511).
+ * For extended x2AVIC, the max index allowed for physical APIC ID table is 0xfff (4095).
  */
 #define X2AVIC_MAX_PHYSICAL_ID		0x1FFUL
+#define X2AVIC_MAX_PHYSICAL_ID_4K	0xFFFUL
 
 static_assert((AVIC_MAX_PHYSICAL_ID & AVIC_PHYSICAL_MAX_INDEX_MASK) == AVIC_MAX_PHYSICAL_ID);
 static_assert((X2AVIC_MAX_PHYSICAL_ID & AVIC_PHYSICAL_MAX_INDEX_MASK) == X2AVIC_MAX_PHYSICAL_ID);
+static_assert((X2AVIC_MAX_PHYSICAL_ID_4K & AVIC_PHYSICAL_MAX_INDEX_4K_MASK) == X2AVIC_MAX_PHYSICAL_ID_4K);
 
 #define AVIC_HPA_MASK	~((0xFFFULL << 52) | 0xFFF)
 
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 65fd245a9953..4c940f4fd34d 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -38,9 +38,9 @@
  * size of the GATag is defined by hardware (32 bits), but is an opaque value
  * as far as hardware is concerned.
  */
-#define AVIC_VCPU_ID_MASK		AVIC_PHYSICAL_MAX_INDEX_MASK
+#define AVIC_VCPU_ID_MASK		AVIC_PHYSICAL_MAX_INDEX_4K_MASK
 
-#define AVIC_VM_ID_SHIFT		HWEIGHT32(AVIC_PHYSICAL_MAX_INDEX_MASK)
+#define AVIC_VM_ID_SHIFT		HWEIGHT32(AVIC_PHYSICAL_MAX_INDEX_4K_MASK)
 #define AVIC_VM_ID_MASK			(GENMASK(31, AVIC_VM_ID_SHIFT) >> AVIC_VM_ID_SHIFT)
 
 #define AVIC_GATAG_TO_VMID(x)		((x >> AVIC_VM_ID_SHIFT) & AVIC_VM_ID_MASK)
@@ -73,6 +73,9 @@ static u32 next_vm_id = 0;
 static bool next_vm_id_wrapped = 0;
 static DEFINE_SPINLOCK(svm_vm_data_hash_lock);
 bool x2avic_enabled;
+static bool x2avic_4k_vcpu_supported;
+static u64 x2avic_max_physical_id;
+static u64 avic_physical_max_index_mask;
 
 /*
  * This is a wrapper of struct amd_iommu_ir_data.
@@ -87,7 +90,7 @@ static void avic_activate_vmcb(struct vcpu_svm *svm)
 	struct vmcb *vmcb = svm->vmcb01.ptr;
 
 	vmcb->control.int_ctl &= ~(AVIC_ENABLE_MASK | X2APIC_MODE_MASK);
-	vmcb->control.avic_physical_id &= ~AVIC_PHYSICAL_MAX_INDEX_MASK;
+	vmcb->control.avic_physical_id &= ~avic_physical_max_index_mask;
 
 	vmcb->control.int_ctl |= AVIC_ENABLE_MASK;
 
@@ -100,7 +103,7 @@ static void avic_activate_vmcb(struct vcpu_svm *svm)
 	 */
 	if (x2avic_enabled && apic_x2apic_mode(svm->vcpu.arch.apic)) {
 		vmcb->control.int_ctl |= X2APIC_MODE_MASK;
-		vmcb->control.avic_physical_id |= X2AVIC_MAX_PHYSICAL_ID;
+		vmcb->control.avic_physical_id |= x2avic_max_physical_id;
 		/* Disabling MSR intercept for x2APIC registers */
 		svm_set_x2apic_msr_interception(svm, false);
 	} else {
@@ -122,7 +125,7 @@ static void avic_deactivate_vmcb(struct vcpu_svm *svm)
 	struct vmcb *vmcb = svm->vmcb01.ptr;
 
 	vmcb->control.int_ctl &= ~(AVIC_ENABLE_MASK | X2APIC_MODE_MASK);
-	vmcb->control.avic_physical_id &= ~AVIC_PHYSICAL_MAX_INDEX_MASK;
+	vmcb->control.avic_physical_id &= ~avic_physical_max_index_mask;
 
 	/*
 	 * If running nested and the guest uses its own MSR bitmap, there
@@ -197,13 +200,15 @@ int avic_vm_init(struct kvm *kvm)
 	struct kvm_svm *k2;
 	struct page *p_page;
 	struct page *l_page;
-	u32 vm_id;
+	u32 vm_id, entries;
 
 	if (!enable_apicv)
 		return 0;
 
-	/* Allocating physical APIC ID table (4KB) */
-	p_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+	/* Allocating physical APIC ID table */
+	entries = x2avic_max_physical_id + 1;
+	p_page = alloc_pages(GFP_KERNEL_ACCOUNT | __GFP_ZERO,
+			     get_order(sizeof(u64) * entries));
 	if (!p_page)
 		goto free_avic;
 
@@ -266,7 +271,7 @@ static u64 *avic_get_physical_id_entry(struct kvm_vcpu *vcpu,
 	struct kvm_svm *kvm_svm = to_kvm_svm(vcpu->kvm);
 
 	if ((!x2avic_enabled && index > AVIC_MAX_PHYSICAL_ID) ||
-	    (index > X2AVIC_MAX_PHYSICAL_ID))
+	    (index > x2avic_max_physical_id))
 		return NULL;
 
 	avic_physical_id_table = page_address(kvm_svm->avic_physical_id_table_page);
@@ -281,7 +286,7 @@ static int avic_init_backing_page(struct kvm_vcpu *vcpu)
 	struct vcpu_svm *svm = to_svm(vcpu);
 
 	if ((!x2avic_enabled && id > AVIC_MAX_PHYSICAL_ID) ||
-	    (id > X2AVIC_MAX_PHYSICAL_ID))
+	    (id > x2avic_max_physical_id))
 		return -EINVAL;
 
 	if (!vcpu->arch.apic->regs)
@@ -493,7 +498,7 @@ int avic_incomplete_ipi_interception(struct kvm_vcpu *vcpu)
 	u32 icrh = svm->vmcb->control.exit_info_1 >> 32;
 	u32 icrl = svm->vmcb->control.exit_info_1;
 	u32 id = svm->vmcb->control.exit_info_2 >> 32;
-	u32 index = svm->vmcb->control.exit_info_2 & 0x1FF;
+	u32 index = svm->vmcb->control.exit_info_2 & avic_physical_max_index_mask;
 	struct kvm_lapic *apic = vcpu->arch.apic;
 
 	trace_kvm_avic_incomplete_ipi(vcpu->vcpu_id, icrh, icrl, id, index);
@@ -1218,8 +1223,19 @@ bool avic_hardware_setup(void)
 
 	/* AVIC is a prerequisite for x2AVIC. */
 	x2avic_enabled = boot_cpu_has(X86_FEATURE_X2AVIC);
-	if (x2avic_enabled)
-		pr_info("x2AVIC enabled\n");
+	if (x2avic_enabled) {
+		x2avic_4k_vcpu_supported = !!(cpuid_ecx(0x8000000a) & 0x40);
+		if (x2avic_4k_vcpu_supported) {
+			x2avic_max_physical_id = X2AVIC_MAX_PHYSICAL_ID_4K;
+			avic_physical_max_index_mask = AVIC_PHYSICAL_MAX_INDEX_4K_MASK;
+		} else {
+			x2avic_max_physical_id = X2AVIC_MAX_PHYSICAL_ID;
+			avic_physical_max_index_mask = AVIC_PHYSICAL_MAX_INDEX_MASK;
+		}
+
+		pr_info("x2AVIC enabled%s\n",
+			x2avic_4k_vcpu_supported ? " (w/ 4K-vcpu)" : "");
+	}
 
 	amd_iommu_register_ga_log_notifier(&avic_ga_log_notifier);
 
-- 
2.48.1

[PATCH v2 2/2] KVM: SVM: Limit AVIC physical max index based on configured max_vcpu_ids

[Naveen N Rao (AMD)]

KVM allows VMMs to specify the maximum possible APIC ID for a virtual
machine through KVM_CAP_MAX_VCPU_ID capability so as to limit data
structures related to APIC/x2APIC. Utilize the same to set the AVIC
physical max index in the VMCB, similar to VMX. This helps hardware
limit the number of entries to be scanned in the physical APIC ID table
speeding up IPI broadcasts for virtual machines with smaller number of
vcpus.

The minimum allocation required for the Physical APIC ID table is one 4k
page supporting up to 512 entries. With AVIC support for 4096 vcpus
though, it is sufficient to only allocate memory to accommodate the
AVIC physical max index that will be programmed into the VMCB. Limit
memory allocated for the Physical APIC ID table accordingly.

Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
---
 arch/x86/kvm/svm/avic.c | 54 ++++++++++++++++++++++++++++++-----------
 arch/x86/kvm/svm/svm.c  |  6 +++++
 arch/x86/kvm/svm/svm.h  |  1 +
 3 files changed, 47 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 4c940f4fd34d..e6ec3bcb1e37 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -85,6 +85,17 @@ struct amd_svm_iommu_ir {
 	void *data;		/* Storing pointer to struct amd_ir_data */
 };
 
+static inline u32 avic_get_max_physical_id(struct kvm *kvm, bool x2apic_mode)
+{
+	u32 avic_max_physical_id = x2apic_mode ? x2avic_max_physical_id : AVIC_MAX_PHYSICAL_ID;
+
+	/*
+	 * Assume vcpu_id is the same as APIC ID. Per KVM_CAP_MAX_VCPU_ID, max_vcpu_ids
+	 * represents the max APIC ID for this vm, rather than the max vcpus.
+	 */
+	return min(kvm->arch.max_vcpu_ids - 1, avic_max_physical_id);
+}
+
 static void avic_activate_vmcb(struct vcpu_svm *svm)
 {
 	struct vmcb *vmcb = svm->vmcb01.ptr;
@@ -103,7 +114,7 @@ static void avic_activate_vmcb(struct vcpu_svm *svm)
 	 */
 	if (x2avic_enabled && apic_x2apic_mode(svm->vcpu.arch.apic)) {
 		vmcb->control.int_ctl |= X2APIC_MODE_MASK;
-		vmcb->control.avic_physical_id |= x2avic_max_physical_id;
+		vmcb->control.avic_physical_id |= avic_get_max_physical_id(svm->vcpu.kvm, true);
 		/* Disabling MSR intercept for x2APIC registers */
 		svm_set_x2apic_msr_interception(svm, false);
 	} else {
@@ -114,7 +125,7 @@ static void avic_activate_vmcb(struct vcpu_svm *svm)
 		kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, &svm->vcpu);
 
 		/* For xAVIC and hybrid-xAVIC modes */
-		vmcb->control.avic_physical_id |= AVIC_MAX_PHYSICAL_ID;
+		vmcb->control.avic_physical_id |= avic_get_max_physical_id(svm->vcpu.kvm, false);
 		/* Enabling MSR intercept for x2APIC registers */
 		svm_set_x2apic_msr_interception(svm, true);
 	}
@@ -174,6 +185,12 @@ int avic_ga_log_notifier(u32 ga_tag)
 	return 0;
 }
 
+static inline int avic_get_physical_id_table_order(struct kvm *kvm)
+{
+	/* Limit to the maximum physical ID supported in x2avic mode */
+	return get_order((avic_get_max_physical_id(kvm, true) + 1) * sizeof(u64));
+}
+
 void avic_vm_destroy(struct kvm *kvm)
 {
 	unsigned long flags;
@@ -185,7 +202,8 @@ void avic_vm_destroy(struct kvm *kvm)
 	if (kvm_svm->avic_logical_id_table_page)
 		__free_page(kvm_svm->avic_logical_id_table_page);
 	if (kvm_svm->avic_physical_id_table_page)
-		__free_page(kvm_svm->avic_physical_id_table_page);
+		__free_pages(kvm_svm->avic_physical_id_table_page,
+			     avic_get_physical_id_table_order(kvm));
 
 	spin_lock_irqsave(&svm_vm_data_hash_lock, flags);
 	hash_del(&kvm_svm->hnode);
@@ -198,22 +216,12 @@ int avic_vm_init(struct kvm *kvm)
 	int err = -ENOMEM;
 	struct kvm_svm *kvm_svm = to_kvm_svm(kvm);
 	struct kvm_svm *k2;
-	struct page *p_page;
 	struct page *l_page;
-	u32 vm_id, entries;
+	u32 vm_id;
 
 	if (!enable_apicv)
 		return 0;
 
-	/* Allocating physical APIC ID table */
-	entries = x2avic_max_physical_id + 1;
-	p_page = alloc_pages(GFP_KERNEL_ACCOUNT | __GFP_ZERO,
-			     get_order(sizeof(u64) * entries));
-	if (!p_page)
-		goto free_avic;
-
-	kvm_svm->avic_physical_id_table_page = p_page;
-
 	/* Allocating logical APIC ID table (4KB) */
 	l_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
 	if (!l_page)
@@ -264,6 +272,24 @@ void avic_init_vmcb(struct vcpu_svm *svm, struct vmcb *vmcb)
 		avic_deactivate_vmcb(svm);
 }
 
+int avic_alloc_physical_id_table(struct kvm *kvm)
+{
+	struct kvm_svm *kvm_svm = to_kvm_svm(kvm);
+	struct page *p_page;
+
+	if (kvm_svm->avic_physical_id_table_page || !enable_apicv || !irqchip_in_kernel(kvm))
+		return 0;
+
+	p_page = alloc_pages(GFP_KERNEL_ACCOUNT | __GFP_ZERO,
+			     avic_get_physical_id_table_order(kvm));
+	if (!p_page)
+		return -ENOMEM;
+
+	kvm_svm->avic_physical_id_table_page = p_page;
+
+	return 0;
+}
+
 static u64 *avic_get_physical_id_entry(struct kvm_vcpu *vcpu,
 				       unsigned int index)
 {
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 7640a84e554a..19b9ebea4773 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1423,6 +1423,11 @@ void svm_switch_vmcb(struct vcpu_svm *svm, struct kvm_vmcb_info *target_vmcb)
 	svm->vmcb = target_vmcb->ptr;
 }
 
+static int svm_vcpu_precreate(struct kvm *kvm)
+{
+	return avic_alloc_physical_id_table(kvm);
+}
+
 static int svm_vcpu_create(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm;
@@ -5009,6 +5014,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
 	.emergency_disable_virtualization_cpu = svm_emergency_disable_virtualization_cpu,
 	.has_emulated_msr = svm_has_emulated_msr,
 
+	.vcpu_precreate = svm_vcpu_precreate,
 	.vcpu_create = svm_vcpu_create,
 	.vcpu_free = svm_vcpu_free,
 	.vcpu_reset = svm_vcpu_reset,
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 9d7cdb8fbf87..68687c3bcce7 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -696,6 +696,7 @@ bool avic_hardware_setup(void);
 int avic_ga_log_notifier(u32 ga_tag);
 void avic_vm_destroy(struct kvm *kvm);
 int avic_vm_init(struct kvm *kvm);
+int avic_alloc_physical_id_table(struct kvm *kvm);
 void avic_init_vmcb(struct vcpu_svm *svm, struct vmcb *vmcb);
 int avic_incomplete_ipi_interception(struct kvm_vcpu *vcpu);
 int avic_unaccelerated_access_interception(struct kvm_vcpu *vcpu);
-- 
2.48.1

Re: [PATCH v2 2/2] KVM: SVM: Limit AVIC physical max index based on configured max_vcpu_ids

[kernel test robot]

Hi Naveen,

kernel test robot noticed the following build errors:

[auto build test ERROR on eb723766b1030a23c38adf2348b7c3d1409d11f0]

url:    https://github.com/intel-lab-lkp/linux/commits/Naveen-N-Rao-AMD/KVM-SVM-Increase-X2AVIC-limit-to-4096-vcpus/20250203-144127
base:   eb723766b1030a23c38adf2348b7c3d1409d11f0
patch link:    https://lore.kernel.org/r/b79610c60de53048f3fda942fd45973c4ab1de97.1738563890.git.naveen%40kernel.org
patch subject: [PATCH v2 2/2] KVM: SVM: Limit AVIC physical max index based on configured max_vcpu_ids
config: x86_64-buildonly-randconfig-003-20250203 (https://download.01.org/0day-ci/archive/20250203/202502031922.dBj76pSx-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250203/202502031922.dBj76pSx-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502031922.dBj76pSx-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from arch/x86/include/asm/kvm_host.h:31,
                    from include/linux/kvm_host.h:45,
                    from arch/x86/kvm/svm/avic.c:20:
>> arch/x86/include/asm/apic.h:258:34: error: expected ')' before numeric constant
     258 | #define x2apic_mode             (0)
         |                                  ^
   arch/x86/kvm/svm/avic.c:88:66: note: in expansion of macro 'x2apic_mode'
      88 | static inline u32 avic_get_max_physical_id(struct kvm *kvm, bool x2apic_mode)
         |                                                                  ^~~~~~~~~~~
   arch/x86/kvm/svm/avic.c: In function 'avic_activate_vmcb':
>> arch/x86/kvm/svm/avic.c:117:51: error: implicit declaration of function 'avic_get_max_physical_id' [-Werror=implicit-function-declaration]
     117 |                 vmcb->control.avic_physical_id |= avic_get_max_physical_id(svm->vcpu.kvm, true);
         |                                                   ^~~~~~~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors


vim +/avic_get_max_physical_id +117 arch/x86/kvm/svm/avic.c

    98	
    99	static void avic_activate_vmcb(struct vcpu_svm *svm)
   100	{
   101		struct vmcb *vmcb = svm->vmcb01.ptr;
   102	
   103		vmcb->control.int_ctl &= ~(AVIC_ENABLE_MASK | X2APIC_MODE_MASK);
   104		vmcb->control.avic_physical_id &= ~avic_physical_max_index_mask;
   105	
   106		vmcb->control.int_ctl |= AVIC_ENABLE_MASK;
   107	
   108		/*
   109		 * Note: KVM supports hybrid-AVIC mode, where KVM emulates x2APIC MSR
   110		 * accesses, while interrupt injection to a running vCPU can be
   111		 * achieved using AVIC doorbell.  KVM disables the APIC access page
   112		 * (deletes the memslot) if any vCPU has x2APIC enabled, thus enabling
   113		 * AVIC in hybrid mode activates only the doorbell mechanism.
   114		 */
   115		if (x2avic_enabled && apic_x2apic_mode(svm->vcpu.arch.apic)) {
   116			vmcb->control.int_ctl |= X2APIC_MODE_MASK;
 > 117			vmcb->control.avic_physical_id |= avic_get_max_physical_id(svm->vcpu.kvm, true);
   118			/* Disabling MSR intercept for x2APIC registers */
   119			svm_set_x2apic_msr_interception(svm, false);
   120		} else {
   121			/*
   122			 * Flush the TLB, the guest may have inserted a non-APIC
   123			 * mapping into the TLB while AVIC was disabled.
   124			 */
   125			kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, &svm->vcpu);
   126	
   127			/* For xAVIC and hybrid-xAVIC modes */
   128			vmcb->control.avic_physical_id |= avic_get_max_physical_id(svm->vcpu.kvm, false);
   129			/* Enabling MSR intercept for x2APIC registers */
   130			svm_set_x2apic_msr_interception(svm, true);
   131		}
   132	}
   133	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v2 2/2] KVM: SVM: Limit AVIC physical max index based on configured max_vcpu_ids

[kernel test robot]

Hi Naveen,

kernel test robot noticed the following build warnings:

[auto build test WARNING on eb723766b1030a23c38adf2348b7c3d1409d11f0]

url:    https://github.com/intel-lab-lkp/linux/commits/Naveen-N-Rao-AMD/KVM-SVM-Increase-X2AVIC-limit-to-4096-vcpus/20250203-144127
base:   eb723766b1030a23c38adf2348b7c3d1409d11f0
patch link:    https://lore.kernel.org/r/b79610c60de53048f3fda942fd45973c4ab1de97.1738563890.git.naveen%40kernel.org
patch subject: [PATCH v2 2/2] KVM: SVM: Limit AVIC physical max index based on configured max_vcpu_ids
config: x86_64-randconfig-008-20250203 (https://download.01.org/0day-ci/archive/20250204/202502040135.UzvbMEPC-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250204/202502040135.UzvbMEPC-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502040135.UzvbMEPC-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from arch/x86/kvm/svm/avic.c:20:
   In file included from include/linux/kvm_host.h:16:
   In file included from include/linux/mm.h:2223:
   include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     518 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
   arch/x86/kvm/svm/avic.c:88:66: error: expected ')'
      88 | static inline u32 avic_get_max_physical_id(struct kvm *kvm, bool x2apic_mode)
         |                                                                  ^
   arch/x86/include/asm/apic.h:258:23: note: expanded from macro 'x2apic_mode'
     258 | #define x2apic_mode             (0)
         |                                  ^
   arch/x86/kvm/svm/avic.c:88:66: note: to match this '('
   arch/x86/include/asm/apic.h:258:22: note: expanded from macro 'x2apic_mode'
     258 | #define x2apic_mode             (0)
         |                                 ^
>> arch/x86/kvm/svm/avic.c:88:66: warning: omitting the parameter name in a function definition is a C23 extension [-Wc23-extensions]
      88 | static inline u32 avic_get_max_physical_id(struct kvm *kvm, bool x2apic_mode)
         |                                                                  ^
   arch/x86/include/asm/apic.h:258:23: note: expanded from macro 'x2apic_mode'
     258 | #define x2apic_mode             (0)
         |                                  ^
   2 warnings and 1 error generated.


vim +88 arch/x86/kvm/svm/avic.c

    87	
  > 88	static inline u32 avic_get_max_physical_id(struct kvm *kvm, bool x2apic_mode)
    89	{
    90		u32 avic_max_physical_id = x2apic_mode ? x2avic_max_physical_id : AVIC_MAX_PHYSICAL_ID;
    91	
    92		/*
    93		 * Assume vcpu_id is the same as APIC ID. Per KVM_CAP_MAX_VCPU_ID, max_vcpu_ids
    94		 * represents the max APIC ID for this vm, rather than the max vcpus.
    95		 */
    96		return min(kvm->arch.max_vcpu_ids - 1, avic_max_physical_id);
    97	}
    98	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v2 2/2] KVM: SVM: Limit AVIC physical max index based on configured max_vcpu_ids

[kernel test robot]

Hi Naveen,

kernel test robot noticed the following build errors:

[auto build test ERROR on eb723766b1030a23c38adf2348b7c3d1409d11f0]

url:    https://github.com/intel-lab-lkp/linux/commits/Naveen-N-Rao-AMD/KVM-SVM-Increase-X2AVIC-limit-to-4096-vcpus/20250203-144127
base:   eb723766b1030a23c38adf2348b7c3d1409d11f0
patch link:    https://lore.kernel.org/r/b79610c60de53048f3fda942fd45973c4ab1de97.1738563890.git.naveen%40kernel.org
patch subject: [PATCH v2 2/2] KVM: SVM: Limit AVIC physical max index based on configured max_vcpu_ids
config: x86_64-randconfig-008-20250203 (https://download.01.org/0day-ci/archive/20250204/202502040421.WqVoesZI-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250204/202502040421.WqVoesZI-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502040421.WqVoesZI-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from arch/x86/kvm/svm/avic.c:20:
   In file included from include/linux/kvm_host.h:16:
   In file included from include/linux/mm.h:2223:
   include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     518 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
>> arch/x86/kvm/svm/avic.c:88:66: error: expected ')'
      88 | static inline u32 avic_get_max_physical_id(struct kvm *kvm, bool x2apic_mode)
         |                                                                  ^
   arch/x86/include/asm/apic.h:258:23: note: expanded from macro 'x2apic_mode'
     258 | #define x2apic_mode             (0)
         |                                  ^
   arch/x86/kvm/svm/avic.c:88:66: note: to match this '('
   arch/x86/include/asm/apic.h:258:22: note: expanded from macro 'x2apic_mode'
     258 | #define x2apic_mode             (0)
         |                                 ^
   arch/x86/kvm/svm/avic.c:88:66: warning: omitting the parameter name in a function definition is a C23 extension [-Wc23-extensions]
      88 | static inline u32 avic_get_max_physical_id(struct kvm *kvm, bool x2apic_mode)
         |                                                                  ^
   arch/x86/include/asm/apic.h:258:23: note: expanded from macro 'x2apic_mode'
     258 | #define x2apic_mode             (0)
         |                                  ^
   2 warnings and 1 error generated.


vim +88 arch/x86/kvm/svm/avic.c

    87	
  > 88	static inline u32 avic_get_max_physical_id(struct kvm *kvm, bool x2apic_mode)
    89	{
    90		u32 avic_max_physical_id = x2apic_mode ? x2avic_max_physical_id : AVIC_MAX_PHYSICAL_ID;
    91	
    92		/*
    93		 * Assume vcpu_id is the same as APIC ID. Per KVM_CAP_MAX_VCPU_ID, max_vcpu_ids
    94		 * represents the max APIC ID for this vm, rather than the max vcpus.
    95		 */
    96		return min(kvm->arch.max_vcpu_ids - 1, avic_max_physical_id);
    97	}
    98	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH v2 2/2] KVM: SVM: Limit AVIC physical max index based on configured max_vcpu_ids

[Vasant Hegde]

Hi Naveen,


On 2/3/2025 12:07 PM, Naveen N Rao (AMD) wrote:
> KVM allows VMMs to specify the maximum possible APIC ID for a virtual
> machine through KVM_CAP_MAX_VCPU_ID capability so as to limit data
> structures related to APIC/x2APIC. Utilize the same to set the AVIC
> physical max index in the VMCB, similar to VMX. This helps hardware
> limit the number of entries to be scanned in the physical APIC ID table
> speeding up IPI broadcasts for virtual machines with smaller number of
> vcpus.
> 
> The minimum allocation required for the Physical APIC ID table is one 4k
> page supporting up to 512 entries. With AVIC support for 4096 vcpus
> though, it is sufficient to only allocate memory to accommodate the
> AVIC physical max index that will be programmed into the VMCB. Limit
> memory allocated for the Physical APIC ID table accordingly.
> 
> Signed-off-by: Naveen N Rao (AMD) <naveen@kernel.org>
> ---
>  arch/x86/kvm/svm/avic.c | 54 ++++++++++++++++++++++++++++++-----------
>  arch/x86/kvm/svm/svm.c  |  6 +++++
>  arch/x86/kvm/svm/svm.h  |  1 +
>  3 files changed, 47 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index 4c940f4fd34d..e6ec3bcb1e37 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -85,6 +85,17 @@ struct amd_svm_iommu_ir {
>  	void *data;		/* Storing pointer to struct amd_ir_data */
>  };
>  
> +static inline u32 avic_get_max_physical_id(struct kvm *kvm, bool x2apic_mode)
> +{
> +	u32 avic_max_physical_id = x2apic_mode ? x2avic_max_physical_id : AVIC_MAX_PHYSICAL_ID;
> +
> +	/*
> +	 * Assume vcpu_id is the same as APIC ID. Per KVM_CAP_MAX_VCPU_ID, max_vcpu_ids
> +	 * represents the max APIC ID for this vm, rather than the max vcpus.
> +	 */
> +	return min(kvm->arch.max_vcpu_ids - 1, avic_max_physical_id);
> +}
> +
>  static void avic_activate_vmcb(struct vcpu_svm *svm)
>  {
>  	struct vmcb *vmcb = svm->vmcb01.ptr;
> @@ -103,7 +114,7 @@ static void avic_activate_vmcb(struct vcpu_svm *svm)
>  	 */
>  	if (x2avic_enabled && apic_x2apic_mode(svm->vcpu.arch.apic)) {
>  		vmcb->control.int_ctl |= X2APIC_MODE_MASK;
> -		vmcb->control.avic_physical_id |= x2avic_max_physical_id;
> +		vmcb->control.avic_physical_id |= avic_get_max_physical_id(svm->vcpu.kvm, true);
>  		/* Disabling MSR intercept for x2APIC registers */
>  		svm_set_x2apic_msr_interception(svm, false);
>  	} else {
> @@ -114,7 +125,7 @@ static void avic_activate_vmcb(struct vcpu_svm *svm)
>  		kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, &svm->vcpu);
>  
>  		/* For xAVIC and hybrid-xAVIC modes */
> -		vmcb->control.avic_physical_id |= AVIC_MAX_PHYSICAL_ID;
> +		vmcb->control.avic_physical_id |= avic_get_max_physical_id(svm->vcpu.kvm, false);
>  		/* Enabling MSR intercept for x2APIC registers */
>  		svm_set_x2apic_msr_interception(svm, true);
>  	}
> @@ -174,6 +185,12 @@ int avic_ga_log_notifier(u32 ga_tag)
>  	return 0;
>  }
>  
> +static inline int avic_get_physical_id_table_order(struct kvm *kvm)
> +{
> +	/* Limit to the maximum physical ID supported in x2avic mode */
> +	return get_order((avic_get_max_physical_id(kvm, true) + 1) * sizeof(u64));
> +}
> +
>  void avic_vm_destroy(struct kvm *kvm)
>  {
>  	unsigned long flags;
> @@ -185,7 +202,8 @@ void avic_vm_destroy(struct kvm *kvm)
>  	if (kvm_svm->avic_logical_id_table_page)
>  		__free_page(kvm_svm->avic_logical_id_table_page);
>  	if (kvm_svm->avic_physical_id_table_page)
> -		__free_page(kvm_svm->avic_physical_id_table_page);
> +		__free_pages(kvm_svm->avic_physical_id_table_page,
> +			     avic_get_physical_id_table_order(kvm));

Move this hunk to previous patch (1/2) ?

Rest looks good.

-Vasant

Re: [PATCH v2 2/2] KVM: SVM: Limit AVIC physical max index based on configured max_vcpu_ids

[Naveen N Rao]

Hi Vasant,

On Wed, Feb 05, 2025 at 12:18:29PM +0530, Vasant Hegde wrote:
> Hi Naveen,
> 
> 
> On 2/3/2025 12:07 PM, Naveen N Rao (AMD) wrote:

<snip>

> >  void avic_vm_destroy(struct kvm *kvm)
> >  {
> >  	unsigned long flags;
> > @@ -185,7 +202,8 @@ void avic_vm_destroy(struct kvm *kvm)
> >  	if (kvm_svm->avic_logical_id_table_page)
> >  		__free_page(kvm_svm->avic_logical_id_table_page);
> >  	if (kvm_svm->avic_physical_id_table_page)
> > -		__free_page(kvm_svm->avic_physical_id_table_page);
> > +		__free_pages(kvm_svm->avic_physical_id_table_page,
> > +			     avic_get_physical_id_table_order(kvm));
> 
> Move this hunk to previous patch (1/2) ?
> 
> Rest looks good.

Sure, thanks for the review!


- Naveen