KVM: SVM: Add initial support for a VMGEXIT VMEXIT

SEV-ES adds a new VMEXIT reason code, VMGEXIT. Initial support for a
VMGEXIT includes mapping the GHCB based on the guest GPA, which is
obtained from a new VMCB field, and then validating the required inputs
for the VMGEXIT exit reason.

Since many of the VMGEXIT exit reasons correspond to existing VMEXIT
reasons, the information from the GHCB is copied into the VMCB control
exit code areas and KVM register areas. The standard exit handlers are
invoked, similar to standard VMEXIT processing. Before restarting the
vCPU, the GHCB is updated with any registers that have been updated by
the hypervisor.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <c6a4ed4294a369bd75c44d03bd7ce0f0c3840e50.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 284 insertions, 2 deletions

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 501adb43ece3..0244f4f244b4 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -18,6 +18,7 @@
 
 #include "x86.h"
 #include "svm.h"
+#include "cpuid.h"
 
 static int sev_flush_asids(void);
 static DECLARE_RWSEM(sev_deactivate_lock);
@@ -1257,11 +1258,226 @@ void sev_free_vcpu(struct kvm_vcpu *vcpu)
 	__free_page(virt_to_page(svm->vmsa));
 }
 
+static void dump_ghcb(struct vcpu_svm *svm)
+{
+	struct ghcb *ghcb = svm->ghcb;
+	unsigned int nbits;
+
+	/* Re-use the dump_invalid_vmcb module parameter */
+	if (!dump_invalid_vmcb) {
+		pr_warn_ratelimited("set kvm_amd.dump_invalid_vmcb=1 to dump internal KVM state.\n");
+		return;
+	}
+
+	nbits = sizeof(ghcb->save.valid_bitmap) * 8;
+
+	pr_err("GHCB (GPA=%016llx):\n", svm->vmcb->control.ghcb_gpa);
+	pr_err("%-20s%016llx is_valid: %u\n", "sw_exit_code",
+	       ghcb->save.sw_exit_code, ghcb_sw_exit_code_is_valid(ghcb));
+	pr_err("%-20s%016llx is_valid: %u\n", "sw_exit_info_1",
+	       ghcb->save.sw_exit_info_1, ghcb_sw_exit_info_1_is_valid(ghcb));
+	pr_err("%-20s%016llx is_valid: %u\n", "sw_exit_info_2",
+	       ghcb->save.sw_exit_info_2, ghcb_sw_exit_info_2_is_valid(ghcb));
+	pr_err("%-20s%016llx is_valid: %u\n", "sw_scratch",
+	       ghcb->save.sw_scratch, ghcb_sw_scratch_is_valid(ghcb));
+	pr_err("%-20s%*pb\n", "valid_bitmap", nbits, ghcb->save.valid_bitmap);
+}
+
+static void sev_es_sync_to_ghcb(struct vcpu_svm *svm)
+{
+	struct kvm_vcpu *vcpu = &svm->vcpu;
+	struct ghcb *ghcb = svm->ghcb;
+
+	/*
+	 * The GHCB protocol so far allows for the following data
+	 * to be returned:
+	 *   GPRs RAX, RBX, RCX, RDX
+	 *
+	 * Copy their values to the GHCB if they are dirty.
+	 */
+	if (kvm_register_is_dirty(vcpu, VCPU_REGS_RAX))
+		ghcb_set_rax(ghcb, vcpu->arch.regs[VCPU_REGS_RAX]);
+	if (kvm_register_is_dirty(vcpu, VCPU_REGS_RBX))
+		ghcb_set_rbx(ghcb, vcpu->arch.regs[VCPU_REGS_RBX]);
+	if (kvm_register_is_dirty(vcpu, VCPU_REGS_RCX))
+		ghcb_set_rcx(ghcb, vcpu->arch.regs[VCPU_REGS_RCX]);
+	if (kvm_register_is_dirty(vcpu, VCPU_REGS_RDX))
+		ghcb_set_rdx(ghcb, vcpu->arch.regs[VCPU_REGS_RDX]);
+}
+
+static void sev_es_sync_from_ghcb(struct vcpu_svm *svm)
+{
+	struct vmcb_control_area *control = &svm->vmcb->control;
+	struct kvm_vcpu *vcpu = &svm->vcpu;
+	struct ghcb *ghcb = svm->ghcb;
+	u64 exit_code;
+
+	/*
+	 * The GHCB protocol so far allows for the following data
+	 * to be supplied:
+	 *   GPRs RAX, RBX, RCX, RDX
+	 *   XCR0
+	 *   CPL
+	 *
+	 * VMMCALL allows the guest to provide extra registers. KVM also
+	 * expects RSI for hypercalls, so include that, too.
+	 *
+	 * Copy their values to the appropriate location if supplied.
+	 */
+	memset(vcpu->arch.regs, 0, sizeof(vcpu->arch.regs));
+
+	vcpu->arch.regs[VCPU_REGS_RAX] = ghcb_get_rax_if_valid(ghcb);
+	vcpu->arch.regs[VCPU_REGS_RBX] = ghcb_get_rbx_if_valid(ghcb);
+	vcpu->arch.regs[VCPU_REGS_RCX] = ghcb_get_rcx_if_valid(ghcb);
+	vcpu->arch.regs[VCPU_REGS_RDX] = ghcb_get_rdx_if_valid(ghcb);
+	vcpu->arch.regs[VCPU_REGS_RSI] = ghcb_get_rsi_if_valid(ghcb);
+
+	svm->vmcb->save.cpl = ghcb_get_cpl_if_valid(ghcb);
+
+	if (ghcb_xcr0_is_valid(ghcb)) {
+		vcpu->arch.xcr0 = ghcb_get_xcr0(ghcb);
+		kvm_update_cpuid_runtime(vcpu);
+	}
+
+	/* Copy the GHCB exit information into the VMCB fields */
+	exit_code = ghcb_get_sw_exit_code(ghcb);
+	control->exit_code = lower_32_bits(exit_code);
+	control->exit_code_hi = upper_32_bits(exit_code);
+	control->exit_info_1 = ghcb_get_sw_exit_info_1(ghcb);
+	control->exit_info_2 = ghcb_get_sw_exit_info_2(ghcb);
+
+	/* Clear the valid entries fields */
+	memset(ghcb->save.valid_bitmap, 0, sizeof(ghcb->save.valid_bitmap));
+}
+
+static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
+{
+	struct kvm_vcpu *vcpu;
+	struct ghcb *ghcb;
+	u64 exit_code = 0;
+
+	ghcb = svm->ghcb;
+
+	/* Only GHCB Usage code 0 is supported */
+	if (ghcb->ghcb_usage)
+		goto vmgexit_err;
+
+	/*
+	 * Retrieve the exit code now even though is may not be marked valid
+	 * as it could help with debugging.
+	 */
+	exit_code = ghcb_get_sw_exit_code(ghcb);
+
+	if (!ghcb_sw_exit_code_is_valid(ghcb) ||
+	    !ghcb_sw_exit_info_1_is_valid(ghcb) ||
+	    !ghcb_sw_exit_info_2_is_valid(ghcb))
+		goto vmgexit_err;
+
+	switch (ghcb_get_sw_exit_code(ghcb)) {
+	case SVM_EXIT_READ_DR7:
+		break;
+	case SVM_EXIT_WRITE_DR7:
+		if (!ghcb_rax_is_valid(ghcb))
+			goto vmgexit_err;
+		break;
+	case SVM_EXIT_RDTSC:
+		break;
+	case SVM_EXIT_RDPMC:
+		if (!ghcb_rcx_is_valid(ghcb))
+			goto vmgexit_err;
+		break;
+	case SVM_EXIT_CPUID:
+		if (!ghcb_rax_is_valid(ghcb) ||
+		    !ghcb_rcx_is_valid(ghcb))
+			goto vmgexit_err;
+		if (ghcb_get_rax(ghcb) == 0xd)
+			if (!ghcb_xcr0_is_valid(ghcb))
+				goto vmgexit_err;
+		break;
+	case SVM_EXIT_INVD:
+		break;
+	case SVM_EXIT_IOIO:
+		if (!(ghcb_get_sw_exit_info_1(ghcb) & SVM_IOIO_TYPE_MASK))
+			if (!ghcb_rax_is_valid(ghcb))
+				goto vmgexit_err;
+		break;
+	case SVM_EXIT_MSR:
+		if (!ghcb_rcx_is_valid(ghcb))
+			goto vmgexit_err;
+		if (ghcb_get_sw_exit_info_1(ghcb)) {
+			if (!ghcb_rax_is_valid(ghcb) ||
+			    !ghcb_rdx_is_valid(ghcb))
+				goto vmgexit_err;
+		}
+		break;
+	case SVM_EXIT_VMMCALL:
+		if (!ghcb_rax_is_valid(ghcb) ||
+		    !ghcb_cpl_is_valid(ghcb))
+			goto vmgexit_err;
+		break;
+	case SVM_EXIT_RDTSCP:
+		break;
+	case SVM_EXIT_WBINVD:
+		break;
+	case SVM_EXIT_MONITOR:
+		if (!ghcb_rax_is_valid(ghcb) ||
+		    !ghcb_rcx_is_valid(ghcb) ||
+		    !ghcb_rdx_is_valid(ghcb))
+			goto vmgexit_err;
+		break;
+	case SVM_EXIT_MWAIT:
+		if (!ghcb_rax_is_valid(ghcb) ||
+		    !ghcb_rcx_is_valid(ghcb))
+			goto vmgexit_err;
+		break;
+	case SVM_VMGEXIT_UNSUPPORTED_EVENT:
+		break;
+	default:
+		goto vmgexit_err;
+	}
+
+	return 0;
+
+vmgexit_err:
+	vcpu = &svm->vcpu;
+
+	if (ghcb->ghcb_usage) {
+		vcpu_unimpl(vcpu, "vmgexit: ghcb usage %#x is not valid\n",
+			    ghcb->ghcb_usage);
+	} else {
+		vcpu_unimpl(vcpu, "vmgexit: exit reason %#llx is not valid\n",
+			    exit_code);
+		dump_ghcb(svm);
+	}
+
+	vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+	vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
+	vcpu->run->internal.ndata = 2;
+	vcpu->run->internal.data[0] = exit_code;
+	vcpu->run->internal.data[1] = vcpu->arch.last_vmentry_cpu;
+
+	return -EINVAL;
+}
+
+static void pre_sev_es_run(struct vcpu_svm *svm)
+{
+	if (!svm->ghcb)
+		return;
+
+	sev_es_sync_to_ghcb(svm);
+
+	kvm_vcpu_unmap(&svm->vcpu, &svm->ghcb_map, true);
+	svm->ghcb = NULL;
+}
+
 void pre_sev_run(struct vcpu_svm *svm, int cpu)
 {
 	struct svm_cpu_data *sd = per_cpu(svm_data, cpu);
 	int asid = sev_get_asid(svm->vcpu.kvm);
 
+	/* Perform any SEV-ES pre-run actions */
+	pre_sev_es_run(svm);
+
 	/* Assign the asid allocated with this SEV guest */
 	svm->asid = asid;
 
@@ -1279,3 +1495,59 @@ void pre_sev_run(struct vcpu_svm *svm, int cpu)
 	svm->vmcb->control.tlb_ctl = TLB_CONTROL_FLUSH_ASID;
 	vmcb_mark_dirty(svm->vmcb, VMCB_ASID);
 }
+
+static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
+{
+	return -EINVAL;
+}
+
+int sev_handle_vmgexit(struct vcpu_svm *svm)
+{
+	struct vmcb_control_area *control = &svm->vmcb->control;
+	u64 ghcb_gpa, exit_code;
+	struct ghcb *ghcb;
+	int ret;
+
+	/* Validate the GHCB */
+	ghcb_gpa = control->ghcb_gpa;
+	if (ghcb_gpa & GHCB_MSR_INFO_MASK)
+		return sev_handle_vmgexit_msr_protocol(svm);
+
+	if (!ghcb_gpa) {
+		vcpu_unimpl(&svm->vcpu, "vmgexit: GHCB gpa is not set\n");
+		return -EINVAL;
+	}
+
+	if (kvm_vcpu_map(&svm->vcpu, ghcb_gpa >> PAGE_SHIFT, &svm->ghcb_map)) {
+		/* Unable to map GHCB from guest */
+		vcpu_unimpl(&svm->vcpu, "vmgexit: error mapping GHCB [%#llx] from guest\n",
+			    ghcb_gpa);
+		return -EINVAL;
+	}
+
+	svm->ghcb = svm->ghcb_map.hva;
+	ghcb = svm->ghcb_map.hva;
+
+	exit_code = ghcb_get_sw_exit_code(ghcb);
+
+	ret = sev_es_validate_vmgexit(svm);
+	if (ret)
+		return ret;
+
+	sev_es_sync_from_ghcb(svm);
+	ghcb_set_sw_exit_info_1(ghcb, 0);
+	ghcb_set_sw_exit_info_2(ghcb, 0);
+
+	ret = -EINVAL;
+	switch (exit_code) {
+	case SVM_VMGEXIT_UNSUPPORTED_EVENT:
+		vcpu_unimpl(&svm->vcpu,
+			    "vmgexit: unsupported event - exit_info_1=%#llx, exit_info_2=%#llx\n",
+			    control->exit_info_1, control->exit_info_2);
+		break;
+	default:
+		ret = svm_invoke_exit_handler(svm, exit_code);
+	}
+
+	return ret;
+}
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 06ea34d61924..310de05d2479 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -194,7 +194,7 @@ module_param(sev, int, 0444);
 int sev_es = IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT);
 module_param(sev_es, int, 0444);
 
-static bool __read_mostly dump_invalid_vmcb = 0;
+bool __read_mostly dump_invalid_vmcb;
 module_param(dump_invalid_vmcb, bool, 0644);
 
 static u8 rsm_ins_bytes[] = "\x0f\xaa";
@@ -2977,6 +2977,7 @@ static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = {
 	[SVM_EXIT_RSM]                          = rsm_interception,
 	[SVM_EXIT_AVIC_INCOMPLETE_IPI]		= avic_incomplete_ipi_interception,
 	[SVM_EXIT_AVIC_UNACCELERATED_ACCESS]	= avic_unaccelerated_access_interception,
+	[SVM_EXIT_VMGEXIT]			= sev_handle_vmgexit,
 };
 
 static void dump_vmcb(struct kvm_vcpu *vcpu)
@@ -3018,6 +3019,7 @@ static void dump_vmcb(struct kvm_vcpu *vcpu)
 	pr_err("%-20s%lld\n", "nested_ctl:", control->nested_ctl);
 	pr_err("%-20s%016llx\n", "nested_cr3:", control->nested_cr3);
 	pr_err("%-20s%016llx\n", "avic_vapic_bar:", control->avic_vapic_bar);
+	pr_err("%-20s%016llx\n", "ghcb:", control->ghcb_gpa);
 	pr_err("%-20s%08x\n", "event_inj:", control->event_inj);
 	pr_err("%-20s%08x\n", "event_inj_err:", control->event_inj_err);
 	pr_err("%-20s%lld\n", "virt_ext:", control->virt_ext);
@@ -3114,7 +3116,7 @@ static int svm_handle_invalid_exit(struct kvm_vcpu *vcpu, u64 exit_code)
 	return -EINVAL;
 }
 
-static int svm_invoke_exit_handler(struct vcpu_svm *svm, u64 exit_code)
+int svm_invoke_exit_handler(struct vcpu_svm *svm, u64 exit_code)
 {
 	if (svm_handle_invalid_exit(&svm->vcpu, exit_code))
 		return 0;
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index abfe53d6b3dc..89bcb26977e5 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -17,6 +17,7 @@
 
 #include <linux/kvm_types.h>
 #include <linux/kvm_host.h>
+#include <linux/bits.h>
 
 #include <asm/svm.h>
 
@@ -172,6 +173,7 @@ struct vcpu_svm {
 	/* SEV-ES support */
 	struct vmcb_save_area *vmsa;
 	struct ghcb *ghcb;
+	struct kvm_host_map ghcb_map;
 };
 
 struct svm_cpu_data {
@@ -390,6 +392,7 @@ static inline bool gif_set(struct vcpu_svm *svm)
 
 extern int sev;
 extern int sev_es;
+extern bool dump_invalid_vmcb;
 
 u32 svm_msrpm_offset(u32 msr);
 u32 *svm_vcpu_alloc_msrpm(void);
@@ -405,6 +408,7 @@ bool svm_smi_blocked(struct kvm_vcpu *vcpu);
 bool svm_nmi_blocked(struct kvm_vcpu *vcpu);
 bool svm_interrupt_blocked(struct kvm_vcpu *vcpu);
 void svm_set_gif(struct vcpu_svm *svm, bool value);
+int svm_invoke_exit_handler(struct vcpu_svm *svm, u64 exit_code);
 
 /* nested.c */
 
@@ -510,6 +514,9 @@ void svm_vcpu_unblocking(struct kvm_vcpu *vcpu);
 
 /* sev.c */
 
+#define GHCB_MSR_INFO_POS		0
+#define GHCB_MSR_INFO_MASK		(BIT_ULL(12) - 1)
+
 extern unsigned int max_sev_asid;
 
 static inline bool svm_sev_enabled(void)
@@ -527,5 +534,6 @@ void pre_sev_run(struct vcpu_svm *svm, int cpu);
 void __init sev_hardware_setup(void);
 void sev_hardware_teardown(void);
 void sev_free_vcpu(struct kvm_vcpu *vcpu);
+int sev_handle_vmgexit(struct vcpu_svm *svm);
 
 #endif