[svsm-devel] [PATCH v3 06/14] x86/sev: Use the SVSM to create a vCPU when not in VMPL0

[Tom Lendacky]

Using the RMPADJUST instruction, the VSMA attribute can only be changed
at VMPL0. An SVSM will be present when running at VMPL1 or a lower
privilege level.

When an SVSM is present, use the SVSM_CORE_CREATE_VCPU call or the
SVSM_CORE_DESTROY_VCPU call to perform VMSA attribute changes. Use the
VMPL level supplied by the SVSM within the VMSA and when starting the
AP.

Signed-off-by: Tom Lendacky <thomas.lendacky at amd.com>
---
 arch/x86/include/asm/sev.h |  2 ++
 arch/x86/kernel/sev.c      | 60 +++++++++++++++++++++++++++++++++-----
 2 files changed, 54 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 204f0a4857d6..d7be613b7372 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -229,6 +229,8 @@ struct svsm_call {
 #define SVSM_CORE_CALL(x)		((0ULL << 32) | (x))
 #define SVSM_CORE_REMAP_CA		0
 #define SVSM_CORE_PVALIDATE		1
+#define SVSM_CORE_CREATE_VCPU		2
+#define SVSM_CORE_DELETE_VCPU		3
 
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 extern void __sev_es_ist_enter(struct pt_regs *regs);
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index d3e182d69d65..ea8b43a0f01b 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -1016,7 +1016,7 @@ void snp_accept_memory(phys_addr_t start, phys_addr_t end)
 	set_pages_state(vaddr, npages, SNP_PAGE_STATE_PRIVATE);
 }
 
-static int snp_set_vmsa(void *va, bool vmsa)
+static int base_snp_set_vmsa(void *va, bool vmsa)
 {
 	u64 attrs;
 
@@ -1034,6 +1034,40 @@ static int snp_set_vmsa(void *va, bool vmsa)
 	return rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs);
 }
 
+static int svsm_snp_set_vmsa(void *va, void *caa, int apic_id, bool vmsa)
+{
+	struct svsm_call call = {};
+	unsigned long flags;
+	int ret;
+
+	local_irq_save(flags);
+
+	call.caa = this_cpu_read(svsm_caa);
+	call.rcx = __pa(va);
+
+	if (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_protocol(&call);
+
+	local_irq_restore(flags);
+
+	return ret;
+}
+
+static int snp_set_vmsa(void *va, void *caa, int apic_id, bool vmsa)
+{
+	return vmpl ? svsm_snp_set_vmsa(va, caa, apic_id, vmsa)
+		    : base_snp_set_vmsa(va, vmsa);
+}
+
 #define __ATTR_BASE		(SVM_SELECTOR_P_MASK | SVM_SELECTOR_S_MASK)
 #define INIT_CS_ATTRIBS		(__ATTR_BASE | SVM_SELECTOR_READ_MASK | SVM_SELECTOR_CODE_MASK)
 #define INIT_DS_ATTRIBS		(__ATTR_BASE | SVM_SELECTOR_WRITE_MASK)
@@ -1065,11 +1099,11 @@ static void *snp_alloc_vmsa_page(void)
 	return page_address(p + 1);
 }
 
-static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa)
+static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa, int apic_id)
 {
 	int err;
 
-	err = snp_set_vmsa(vmsa, false);
+	err = snp_set_vmsa(vmsa, NULL, apic_id, false);
 	if (err)
 		pr_err("clear VMSA page failed (%u), leaking page\n", err);
 	else
@@ -1080,6 +1114,7 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
 {
 	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;
@@ -1126,6 +1161,12 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
 	if (!vmsa)
 		return -ENOMEM;
 
+	/*
+	 * If an SVSM is present, then the SVSM CAA per-CPU variable will
+	 * have a value, otherwise it will be NULL.
+	 */
+	caa = per_cpu(svsm_caa, cpu);
+
 	/* CR4 should maintain the MCE value */
 	cr4 = native_read_cr4() & X86_CR4_MCE;
 
@@ -1173,11 +1214,11 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
 	 *   VMPL level
 	 *   SEV_FEATURES (matches the SEV STATUS MSR right shifted 2 bits)
 	 */
-	vmsa->vmpl		= 0;
+	vmsa->vmpl		= vmpl;
 	vmsa->sev_features	= sev_status >> 2;
 
 	/* Switch the page over to a VMSA page now that it is initialized */
-	ret = snp_set_vmsa(vmsa, true);
+	ret = snp_set_vmsa(vmsa, caa, apic_id, true);
 	if (ret) {
 		pr_err("set VMSA page failed (%u)\n", ret);
 		free_page((unsigned long)vmsa);
@@ -1193,7 +1234,10 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
 	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) | SVM_VMGEXIT_AP_CREATE);
+	ghcb_set_sw_exit_info_1(ghcb,
+				((u64)apic_id << 32)	|
+				((u64)vmpl << 16)	|
+				SVM_VMGEXIT_AP_CREATE);
 	ghcb_set_sw_exit_info_2(ghcb, __pa(vmsa));
 
 	sev_es_wr_ghcb_msr(__pa(ghcb));
@@ -1211,13 +1255,13 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
 
 	/* Perform cleanup if there was an error */
 	if (ret) {
-		snp_cleanup_vmsa(vmsa);
+		snp_cleanup_vmsa(vmsa, apic_id);
 		vmsa = NULL;
 	}
 
 	/* Free up any previous VMSA page */
 	if (cur_vmsa)
-		snp_cleanup_vmsa(cur_vmsa);
+		snp_cleanup_vmsa(cur_vmsa, apic_id);
 
 	/* Record the current VMSA page */
 	per_cpu(sev_vmsa, cpu) = vmsa;
-- 
2.43.2