[PATCH 02/11] Drivers: hv: Move hv_vp_assist_page to common files

[Naman Jain <namjain@linux.microsoft.com>]

Move the logic to initialize and export hv_vp_assist_page from x86
architecture code to Hyper-V common code to allow it to be used for
upcoming arm64 support in MSHV_VTL driver.
Note: This change also improves error handling - if VP assist page
allocation fails, hyperv_init() now returns early instead of
continuing with partial initialization.

Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
---
 arch/x86/hyperv/hv_init.c      | 88 +---------------------------------
 drivers/hv/hv_common.c         | 88 ++++++++++++++++++++++++++++++++++
 include/asm-generic/mshyperv.h |  4 ++
 include/hyperv/hvgdk_mini.h    |  2 +
 4 files changed, 95 insertions(+), 87 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 323adc93f2dc..75a98b5e451b 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -81,9 +81,6 @@ union hv_ghcb * __percpu *hv_ghcb_pg;
 /* Storage to save the hypercall page temporarily for hibernation */
 static void *hv_hypercall_pg_saved;
 
-struct hv_vp_assist_page **hv_vp_assist_page;
-EXPORT_SYMBOL_GPL(hv_vp_assist_page);
-
 static int hyperv_init_ghcb(void)
 {
 	u64 ghcb_gpa;
@@ -117,59 +114,12 @@ static int hyperv_init_ghcb(void)
 
 static int hv_cpu_init(unsigned int cpu)
 {
-	union hv_vp_assist_msr_contents msr = { 0 };
-	struct hv_vp_assist_page **hvp;
 	int ret;
 
 	ret = hv_common_cpu_init(cpu);
 	if (ret)
 		return ret;
 
-	if (!hv_vp_assist_page)
-		return 0;
-
-	hvp = &hv_vp_assist_page[cpu];
-	if (hv_root_partition()) {
-		/*
-		 * For root partition we get the hypervisor provided VP assist
-		 * page, instead of allocating a new page.
-		 */
-		rdmsrq(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
-		*hvp = memremap(msr.pfn << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT,
-				PAGE_SIZE, MEMREMAP_WB);
-	} else {
-		/*
-		 * The VP assist page is an "overlay" page (see Hyper-V TLFS's
-		 * Section 5.2.1 "GPA Overlay Pages"). Here it must be zeroed
-		 * out to make sure we always write the EOI MSR in
-		 * hv_apic_eoi_write() *after* the EOI optimization is disabled
-		 * in hv_cpu_die(), otherwise a CPU may not be stopped in the
-		 * case of CPU offlining and the VM will hang.
-		 */
-		if (!*hvp) {
-			*hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL | __GFP_ZERO);
-
-			/*
-			 * Hyper-V should never specify a VM that is a Confidential
-			 * VM and also running in the root partition. Root partition
-			 * is blocked to run in Confidential VM. So only decrypt assist
-			 * page in non-root partition here.
-			 */
-			if (*hvp && !ms_hyperv.paravisor_present && hv_isolation_type_snp()) {
-				WARN_ON_ONCE(set_memory_decrypted((unsigned long)(*hvp), 1));
-				memset(*hvp, 0, PAGE_SIZE);
-			}
-		}
-
-		if (*hvp)
-			msr.pfn = vmalloc_to_pfn(*hvp);
-
-	}
-	if (!WARN_ON(!(*hvp))) {
-		msr.enable = 1;
-		wrmsrq(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
-	}
-
 	/* Allow Hyper-V stimer vector to be injected from Hypervisor. */
 	if (ms_hyperv.misc_features & HV_STIMER_DIRECT_MODE_AVAILABLE)
 		apic_update_vector(cpu, HYPERV_STIMER0_VECTOR, true);
@@ -286,23 +236,6 @@ static int hv_cpu_die(unsigned int cpu)
 
 	hv_common_cpu_die(cpu);
 
-	if (hv_vp_assist_page && hv_vp_assist_page[cpu]) {
-		union hv_vp_assist_msr_contents msr = { 0 };
-		if (hv_root_partition()) {
-			/*
-			 * For root partition the VP assist page is mapped to
-			 * hypervisor provided page, and thus we unmap the
-			 * page here and nullify it, so that in future we have
-			 * correct page address mapped in hv_cpu_init.
-			 */
-			memunmap(hv_vp_assist_page[cpu]);
-			hv_vp_assist_page[cpu] = NULL;
-			rdmsrq(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
-			msr.enable = 0;
-		}
-		wrmsrq(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
-	}
-
 	if (hv_reenlightenment_cb == NULL)
 		return 0;
 
@@ -460,21 +393,6 @@ void __init hyperv_init(void)
 	if (hv_common_init())
 		return;
 
-	/*
-	 * The VP assist page is useless to a TDX guest: the only use we
-	 * would have for it is lazy EOI, which can not be used with TDX.
-	 */
-	if (hv_isolation_type_tdx())
-		hv_vp_assist_page = NULL;
-	else
-		hv_vp_assist_page = kzalloc_objs(*hv_vp_assist_page, nr_cpu_ids);
-	if (!hv_vp_assist_page) {
-		ms_hyperv.hints &= ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
-
-		if (!hv_isolation_type_tdx())
-			goto common_free;
-	}
-
 	if (ms_hyperv.paravisor_present && hv_isolation_type_snp()) {
 		/* Negotiate GHCB Version. */
 		if (!hv_ghcb_negotiate_protocol())
@@ -483,7 +401,7 @@ void __init hyperv_init(void)
 
 		hv_ghcb_pg = alloc_percpu(union hv_ghcb *);
 		if (!hv_ghcb_pg)
-			goto free_vp_assist_page;
+			goto free_ghcb_page;
 	}
 
 	cpuhp = cpuhp_setup_state(CPUHP_AP_HYPERV_ONLINE, "x86/hyperv_init:online",
@@ -613,10 +531,6 @@ void __init hyperv_init(void)
 	cpuhp_remove_state(CPUHP_AP_HYPERV_ONLINE);
 free_ghcb_page:
 	free_percpu(hv_ghcb_pg);
-free_vp_assist_page:
-	kfree(hv_vp_assist_page);
-	hv_vp_assist_page = NULL;
-common_free:
 	hv_common_free();
 }
 
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 6b67ac616789..d1ebc0ebd08f 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -28,7 +28,9 @@
 #include <linux/slab.h>
 #include <linux/dma-map-ops.h>
 #include <linux/set_memory.h>
+#include <linux/vmalloc.h>
 #include <hyperv/hvhdk.h>
+#include <hyperv/hvgdk.h>
 #include <asm/mshyperv.h>
 
 u64 hv_current_partition_id = HV_PARTITION_ID_SELF;
@@ -78,6 +80,8 @@ static struct ctl_table_header *hv_ctl_table_hdr;
 u8 * __percpu *hv_synic_eventring_tail;
 EXPORT_SYMBOL_GPL(hv_synic_eventring_tail);
 
+struct hv_vp_assist_page **hv_vp_assist_page;
+EXPORT_SYMBOL_GPL(hv_vp_assist_page);
 /*
  * Hyper-V specific initialization and shutdown code that is
  * common across all architectures.  Called from architecture
@@ -92,6 +96,9 @@ void __init hv_common_free(void)
 	if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE)
 		hv_kmsg_dump_unregister();
 
+	kfree(hv_vp_assist_page);
+	hv_vp_assist_page = NULL;
+
 	kfree(hv_vp_index);
 	hv_vp_index = NULL;
 
@@ -394,6 +401,23 @@ int __init hv_common_init(void)
 	for (i = 0; i < nr_cpu_ids; i++)
 		hv_vp_index[i] = VP_INVAL;
 
+	/*
+	 * The VP assist page is useless to a TDX guest: the only use we
+	 * would have for it is lazy EOI, which can not be used with TDX.
+	 */
+	if (hv_isolation_type_tdx()) {
+		hv_vp_assist_page = NULL;
+	} else {
+		hv_vp_assist_page = kzalloc_objs(*hv_vp_assist_page, nr_cpu_ids);
+		if (!hv_vp_assist_page) {
+#ifdef CONFIG_X86_64
+			ms_hyperv.hints &= ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
+#endif
+			hv_common_free();
+			return -ENOMEM;
+		}
+	}
+
 	return 0;
 }
 
@@ -471,6 +495,8 @@ void __init ms_hyperv_late_init(void)
 
 int hv_common_cpu_init(unsigned int cpu)
 {
+	union hv_vp_assist_msr_contents msr = { 0 };
+	struct hv_vp_assist_page **hvp;
 	void **inputarg, **outputarg;
 	u8 **synic_eventring_tail;
 	u64 msr_vp_index;
@@ -542,6 +568,50 @@ int hv_common_cpu_init(unsigned int cpu)
 			ret = -ENOMEM;
 	}
 
+	if (!hv_vp_assist_page)
+		return ret;
+
+	hvp = &hv_vp_assist_page[cpu];
+	if (hv_root_partition()) {
+		/*
+		 * For root partition we get the hypervisor provided VP assist
+		 * page, instead of allocating a new page.
+		 */
+		msr.as_uint64 = hv_get_msr(HV_SYN_REG_VP_ASSIST_PAGE);
+		*hvp = memremap(msr.pfn << HV_VP_ASSIST_PAGE_ADDRESS_SHIFT,
+				PAGE_SIZE, MEMREMAP_WB);
+	} else {
+		/*
+		 * The VP assist page is an "overlay" page (see Hyper-V TLFS's
+		 * Section 5.2.1 "GPA Overlay Pages"). Here it must be zeroed
+		 * out to make sure we always write the EOI MSR in
+		 * hv_apic_eoi_write() *after* the EOI optimization is disabled
+		 * in hv_cpu_die(), otherwise a CPU may not be stopped in the
+		 * case of CPU offlining and the VM will hang.
+		 */
+		if (!*hvp) {
+			*hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL | __GFP_ZERO);
+
+			/*
+			 * Hyper-V should never specify a VM that is a Confidential
+			 * VM and also running in the root partition. Root partition
+			 * is blocked to run in Confidential VM. So only decrypt assist
+			 * page in non-root partition here.
+			 */
+			if (*hvp && !ms_hyperv.paravisor_present && hv_isolation_type_snp()) {
+				WARN_ON_ONCE(set_memory_decrypted((unsigned long)(*hvp), 1));
+				memset(*hvp, 0, PAGE_SIZE);
+			}
+		}
+
+		if (*hvp)
+			msr.pfn = vmalloc_to_pfn(*hvp);
+	}
+	if (!WARN_ON(!(*hvp))) {
+		msr.enable = 1;
+		hv_set_msr(HV_SYN_REG_VP_ASSIST_PAGE, msr.as_uint64);
+	}
+
 	return ret;
 }
 
@@ -566,6 +636,24 @@ int hv_common_cpu_die(unsigned int cpu)
 		*synic_eventring_tail = NULL;
 	}
 
+	if (hv_vp_assist_page && hv_vp_assist_page[cpu]) {
+		union hv_vp_assist_msr_contents msr = { 0 };
+
+		if (hv_root_partition()) {
+			/*
+			 * For root partition the VP assist page is mapped to
+			 * hypervisor provided page, and thus we unmap the
+			 * page here and nullify it, so that in future we have
+			 * correct page address mapped in hv_cpu_init.
+			 */
+			memunmap(hv_vp_assist_page[cpu]);
+			hv_vp_assist_page[cpu] = NULL;
+			msr.as_uint64 = hv_get_msr(HV_SYN_REG_VP_ASSIST_PAGE);
+			msr.enable = 0;
+		}
+		hv_set_msr(HV_SYN_REG_VP_ASSIST_PAGE, msr.as_uint64);
+	}
+
 	return 0;
 }
 
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index d37b68238c97..108f135d4fd9 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -25,6 +25,7 @@
 #include <linux/nmi.h>
 #include <asm/ptrace.h>
 #include <hyperv/hvhdk.h>
+#include <hyperv/hvgdk.h>
 
 #define VTPM_BASE_ADDRESS 0xfed40000
 
@@ -299,6 +300,8 @@ do { \
 #define hv_status_debug(status, fmt, ...) \
 	hv_status_printk(debug, status, fmt, ##__VA_ARGS__)
 
+extern struct hv_vp_assist_page **hv_vp_assist_page;
+
 const char *hv_result_to_string(u64 hv_status);
 int hv_result_to_errno(u64 status);
 void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die);
@@ -377,6 +380,7 @@ static inline int hv_deposit_memory(u64 partition_id, u64 status)
 	return hv_deposit_memory_node(NUMA_NO_NODE, partition_id, status);
 }
 
+#define HV_VP_ASSIST_PAGE_ADDRESS_SHIFT	12
 #if IS_ENABLED(CONFIG_HYPERV_VTL_MODE)
 u8 __init get_vtl(void);
 #else
diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
index 056ef7b6b360..be697ddb211a 100644
--- a/include/hyperv/hvgdk_mini.h
+++ b/include/hyperv/hvgdk_mini.h
@@ -149,6 +149,7 @@ struct hv_u128 {
 #define HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT	12
 #define HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_MASK	\
 		(~((1ull << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT) - 1))
+#define HV_SYN_REG_VP_ASSIST_PAGE              (HV_X64_MSR_VP_ASSIST_PAGE)
 
 /* Hyper-V Enlightened VMCS version mask in nested features CPUID */
 #define HV_X64_ENLIGHTENED_VMCS_VERSION		0xff
@@ -1185,6 +1186,7 @@ enum hv_register_name {
 
 #define HV_MSR_STIMER0_CONFIG	(HV_REGISTER_STIMER0_CONFIG)
 #define HV_MSR_STIMER0_COUNT	(HV_REGISTER_STIMER0_COUNT)
+#define HV_SYN_REG_VP_ASSIST_PAGE    (HV_REGISTER_VP_ASSIST_PAGE)
 
 #endif /* CONFIG_ARM64 */
 
-- 
2.43.0