Merge: SEV-SNP: kdump fixes

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/6960

JIRA: https://issues.redhat.com/browse/RHEL-10019

These changes allow the guest kernel to get a dump onto the local path
when running sev-snp guests.

Signed-off-by: Bandan Das <bsd@redhat.com>

Approved-by: Maxim Levitsky <mlevitsk@redhat.com>
Approved-by: John Allen <johnalle@redhat.com>
Approved-by: Thomas Huth <thuth@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Augusto Caringi <acaringi@redhat.com>

Author: caringi

arch/x86/coco/sev/core.c

@@ -1010,6 +1010,102 @@ void snp_accept_memory(phys_addr_t start, phys_addr_t end)
 	set_pages_state(vaddr, npages, SNP_PAGE_STATE_PRIVATE);
 }
 
+static int vmgexit_ap_control(u64 event, struct sev_es_save_area *vmsa, u32 apic_id)
+{
+	bool create = event != SVM_VMGEXIT_AP_DESTROY;
+	struct ghcb_state state;
+	unsigned long flags;
+	struct ghcb *ghcb;
+	int ret = 0;
+
+	local_irq_save(flags);
+
+	ghcb = __sev_get_ghcb(&state);
+
+	vc_ghcb_invalidate(ghcb);
+
+	if (create)
+		ghcb_set_rax(ghcb, vmsa->sev_features);
+
+	ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_CREATION);
+	ghcb_set_sw_exit_info_1(ghcb,
+				((u64)apic_id << 32)	|
+				((u64)snp_vmpl << 16)	|
+				event);
+	ghcb_set_sw_exit_info_2(ghcb, __pa(vmsa));
+
+	sev_es_wr_ghcb_msr(__pa(ghcb));
+	VMGEXIT();
+
+	if (!ghcb_sw_exit_info_1_is_valid(ghcb) ||
+	    lower_32_bits(ghcb->save.sw_exit_info_1)) {
+		pr_err("SNP AP %s error\n", (create ? "CREATE" : "DESTROY"));
+		ret = -EINVAL;
+	}
+
+	__sev_put_ghcb(&state);
+
+	local_irq_restore(flags);
+
+	return ret;
+}
+
+static int snp_set_vmsa(void *va, void *caa, int apic_id, bool make_vmsa)
+{
+	int ret;
+
+	if (snp_vmpl) {
+		struct svsm_call call = {};
+		unsigned long flags;
+
+		local_irq_save(flags);
+
+		call.caa = this_cpu_read(svsm_caa);
+		call.rcx = __pa(va);
+
+		if (make_vmsa) {
+			/* Protocol 0, Call ID 2 */
+			call.rax = SVSM_CORE_CALL(SVSM_CORE_CREATE_VCPU);
+			call.rdx = __pa(caa);
+			call.r8  = apic_id;
+		} else {
+			/* Protocol 0, Call ID 3 */
+			call.rax = SVSM_CORE_CALL(SVSM_CORE_DELETE_VCPU);
+		}
+
+		ret = svsm_perform_call_protocol(&call);
+
+		local_irq_restore(flags);
+	} else {
+		/*
+		 * If the kernel runs at VMPL0, it can change the VMSA
+		 * bit for a page using the RMPADJUST instruction.
+		 * However, for the instruction to succeed it must
+		 * target the permissions of a lesser privileged (higher
+		 * numbered) VMPL level, so use VMPL1.
+		 */
+		u64 attrs = 1;
+
+		if (make_vmsa)
+			attrs |= RMPADJUST_VMSA_PAGE_BIT;
+
+		ret = rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs);
+	}
+
+	return ret;
+}
+
+static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa, int apic_id)
+{
+	int err;
+
+	err = snp_set_vmsa(vmsa, NULL, apic_id, false);
+	if (err)
+		pr_err("clear VMSA page failed (%u), leaking page\n", err);
+	else
+		free_page((unsigned long)vmsa);
+}
+
 static void set_pte_enc(pte_t *kpte, int level, void *va)
 {
 	struct pte_enc_desc d = {
@@ -1056,7 +1152,8 @@ static void unshare_all_memory(void)
 			data = per_cpu(runtime_data, cpu);
 			ghcb = (unsigned long)&data->ghcb_page;
 
-			if (addr <= ghcb && ghcb <= addr + size) {
+			/* Handle the case of a huge page containing the GHCB page */
+			if (addr <= ghcb && ghcb < addr + size) {
 				skipped_addr = true;
 				break;
 			}
@@ -1106,11 +1203,70 @@ void snp_kexec_begin(void)
 		pr_warn("Failed to stop shared<->private conversions\n");
 }
 
+/*
+ * Shutdown all APs except the one handling kexec/kdump and clearing
+ * the VMSA tag on AP's VMSA pages as they are not being used as
+ * VMSA page anymore.
+ */
+static void shutdown_all_aps(void)
+{
+	struct sev_es_save_area *vmsa;
+	int apic_id, this_cpu, cpu;
+
+	this_cpu = get_cpu();
+
+	/*
+	 * APs are already in HLT loop when enc_kexec_finish() callback
+	 * is invoked.
+	 */
+	for_each_present_cpu(cpu) {
+		vmsa = per_cpu(sev_vmsa, cpu);
+
+		/*
+		 * The BSP or offlined APs do not have guest allocated VMSA
+		 * and there is no need  to clear the VMSA tag for this page.
+		 */
+		if (!vmsa)
+			continue;
+
+		/*
+		 * Cannot clear the VMSA tag for the currently running vCPU.
+		 */
+		if (this_cpu == cpu) {
+			unsigned long pa;
+			struct page *p;
+
+			pa = __pa(vmsa);
+			/*
+			 * Mark the VMSA page of the running vCPU as offline
+			 * so that is excluded and not touched by makedumpfile
+			 * while generating vmcore during kdump.
+			 */
+			p = pfn_to_online_page(pa >> PAGE_SHIFT);
+			if (p)
+				__SetPageOffline(p);
+			continue;
+		}
+
+		apic_id = cpuid_to_apicid[cpu];
+
+		/*
+		 * Issue AP destroy to ensure AP gets kicked out of guest mode
+		 * to allow using RMPADJUST to remove the VMSA tag on it's
+		 * VMSA page.
+		 */
+		vmgexit_ap_control(SVM_VMGEXIT_AP_DESTROY, vmsa, apic_id);
+		snp_cleanup_vmsa(vmsa, apic_id);
+	}
+
+	put_cpu();
+}
+
 void snp_kexec_finish(void)
 {
 	struct sev_es_runtime_data *data;
+	unsigned long size, addr;
 	unsigned int level, cpu;
-	unsigned long size;
 	struct ghcb *ghcb;
 	pte_t *pte;
 
@@ -1120,6 +1276,8 @@ void snp_kexec_finish(void)
 	if (!IS_ENABLED(CONFIG_KEXEC_CORE))
 		return;
 
+	shutdown_all_aps();
+
 	unshare_all_memory();
 
 	/*
@@ -1136,54 +1294,11 @@ void snp_kexec_finish(void)
 		ghcb = &data->ghcb_page;
 		pte = lookup_address((unsigned long)ghcb, &level);
 		size = page_level_size(level);
-		set_pte_enc(pte, level, (void *)ghcb);
-		snp_set_memory_private((unsigned long)ghcb, (size / PAGE_SIZE));
-	}
-}
-
-static int snp_set_vmsa(void *va, void *caa, int apic_id, bool make_vmsa)
-{
-	int ret;
-
-	if (snp_vmpl) {
-		struct svsm_call call = {};
-		unsigned long flags;
-
-		local_irq_save(flags);
-
-		call.caa = this_cpu_read(svsm_caa);
-		call.rcx = __pa(va);
-
-		if (make_vmsa) {
-			/* Protocol 0, Call ID 2 */
-			call.rax = SVSM_CORE_CALL(SVSM_CORE_CREATE_VCPU);
-			call.rdx = __pa(caa);
-			call.r8  = apic_id;
-		} else {
-			/* Protocol 0, Call ID 3 */
-			call.rax = SVSM_CORE_CALL(SVSM_CORE_DELETE_VCPU);
-		}
-
-		ret = svsm_perform_call_protocol(&call);
-
-		local_irq_restore(flags);
-	} else {
-		/*
-		 * If the kernel runs at VMPL0, it can change the VMSA
-		 * bit for a page using the RMPADJUST instruction.
-		 * However, for the instruction to succeed it must
-		 * target the permissions of a lesser privileged (higher
-		 * numbered) VMPL level, so use VMPL1.
-		 */
-		u64 attrs = 1;
-
-		if (make_vmsa)
-			attrs |= RMPADJUST_VMSA_PAGE_BIT;
-
-		ret = rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs);
+		/* Handle the case of a huge page containing the GHCB page */
+		addr = (unsigned long)ghcb & page_level_mask(level);
+		set_pte_enc(pte, level, (void *)addr);
+		snp_set_memory_private(addr, (size / PAGE_SIZE));
 	}
-
-	return ret;
 }
 
 #define __ATTR_BASE		(SVM_SELECTOR_P_MASK | SVM_SELECTOR_S_MASK)
@@ -1217,24 +1332,10 @@ static void *snp_alloc_vmsa_page(void)
 	return page_address(p + 1);
 }
 
-static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa, int apic_id)
-{
-	int err;
-
-	err = snp_set_vmsa(vmsa, NULL, apic_id, false);
-	if (err)
-		pr_err("clear VMSA page failed (%u), leaking page\n", err);
-	else
-		free_page((unsigned long)vmsa);
-}
-
 static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip, unsigned int cpu)
 {
 	struct sev_es_save_area *cur_vmsa, *vmsa;
-	struct ghcb_state state;
 	struct svsm_ca *caa;
-	unsigned long flags;
-	struct ghcb *ghcb;
 	u8 sipi_vector;
 	int ret;
 	u64 cr4;
@@ -1333,33 +1434,7 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip, unsigned
 	}
 
 	/* Issue VMGEXIT AP Creation NAE event */
-	local_irq_save(flags);
-
-	ghcb = __sev_get_ghcb(&state);
-
-	vc_ghcb_invalidate(ghcb);
-	ghcb_set_rax(ghcb, vmsa->sev_features);
-	ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_AP_CREATION);
-	ghcb_set_sw_exit_info_1(ghcb,
-				((u64)apic_id << 32)	|
-				((u64)snp_vmpl << 16)	|
-				SVM_VMGEXIT_AP_CREATE);
-	ghcb_set_sw_exit_info_2(ghcb, __pa(vmsa));
-
-	sev_es_wr_ghcb_msr(__pa(ghcb));
-	VMGEXIT();
-
-	if (!ghcb_sw_exit_info_1_is_valid(ghcb) ||
-	    lower_32_bits(ghcb->save.sw_exit_info_1)) {
-		pr_err("SNP AP Creation error\n");
-		ret = -EINVAL;
-	}
-
-	__sev_put_ghcb(&state);
-
-	local_irq_restore(flags);
-
-	/* Perform cleanup if there was an error */
+	ret = vmgexit_ap_control(SVM_VMGEXIT_AP_CREATE, vmsa, apic_id);
 	if (ret) {
 		snp_cleanup_vmsa(vmsa, apic_id);
 		vmsa = NULL;