[RFC PATCH 09/12] arm64: [HACK] Show extra info about SVE with --show-reg-list

[Dave Martin <Dave.Martin@arm.com>]

This patch prints out some information about the SVE configuration
when --show-reg=list is passed.

This is development hack only (as well as being an abuse of the
purpose of that option).

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
---
 arm/kvm-cpu.c | 111 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 110 insertions(+), 1 deletion(-)

diff --git a/arm/kvm-cpu.c b/arm/kvm-cpu.c
index 38a071b..80e7b79 100644
--- a/arm/kvm-cpu.c
+++ b/arm/kvm-cpu.c
@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <errno.h>
 #include <stddef.h>
 #include <stdio.h>
@@ -48,6 +49,112 @@ error:
 	return ret;
 }
 
+static int kvm_show_sve_info(struct kvm_cpu const *vcpu)
+{
+	int ret = 0;
+	u64 val;
+	struct kvm_one_reg r;
+	int have_sve;
+	u64 vls[9];
+	unsigned int i;
+
+	r.addr = (u64)&val;
+
+	r.id = ARM64_SYS_REG(3, 0, 0, 4, 0); /* ID_AA64PFR0_EL1 */
+	assert((r.id & KVM_REG_SIZE_MASK) == KVM_REG_SIZE_U64);
+	if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, &r)) {
+		perror("KVM_GET_ONE_REG(ID_AA64PFR0_EL1)");
+		goto error;
+	}
+
+	printf("ID_AA64PFR0_EL1:\t0x%lx\n", (unsigned long)val);
+
+	have_sve = !!((val >> 32) & 0xf);
+
+	r.id = ARM64_SYS_REG(3, 0, 0, 4, 4);
+	if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, &r)) {
+		if (errno != ENOENT || have_sve) {
+			perror("KVM_GET_ONE_REG(ID_AA64ZFR0_EL1)");
+			ret = -1;
+		}
+	} else {
+		if (!have_sve) {
+			puts("ID_AA64ZFR0_EL1 unexpectedly present");
+			ret = -1;
+		}
+
+		printf("ID_AA64ZFR0_EL1:\t0x%lx\n", (unsigned long)val);
+	}
+
+	r.id = ARM64_SYS_REG(3, 0, 1, 2, 0);
+	if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, &r)) {
+		if (errno != ENOENT || have_sve) {
+			perror("KVM_GET_ONE_REG(ZCR_EL1)");
+			ret = -1;
+		}
+	} else {
+		if (!have_sve) {
+			puts("ZCR_EL1 unexpectedly present");
+			ret = -1;
+		}
+
+		printf("ZCR_EL1:\t0x%lx\n", (unsigned long)val);
+	}
+
+	r.addr = (u64)&vls;
+	r.id = KVM_REG_ARM64_SVE_VLS;
+	assert(8 * (sizeof(vls) - sizeof(*vls)) == 512 &&
+	       (r.id & KVM_REG_SIZE_MASK) == KVM_REG_SIZE_U512);
+
+	/*
+	 * Write some canary data so we can see that the kernel writes
+	 * the expected amount:
+	 */
+	for (i = 0; i < sizeof(vls) / sizeof(*vls); ++i)
+		vls[i] = -7;
+
+	if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, &r)) {
+		if (errno != ENOENT || have_sve) {
+			perror("KVM_GET_ONE_REG(KVM_REG_ARM64_SVE_VLS)");
+			ret = -1;
+		}
+	} else {
+		char const *prefix = "";
+
+		if (!have_sve) {
+			puts("KVM_REG_ARM64_SVE_VLS unexpectedly present");
+			ret = -1;
+		}
+
+		if (vls[7] == (u64)-7) {
+			puts("KVM_REG_ARM64_SVE_VLS short read?");
+			ret = -1;
+		}
+
+		if (vls[8] != (u64)-7) {
+			puts("KVM_REG_ARM64_SVE_VLS overrun?");
+			ret = -1;
+		}
+
+		fputs("SVE VQs: ", stdout);
+
+		for (i = 0; i < 512; ++i)
+			if ((vls[i / 64] >> (i % 64)) & 1) {
+				printf("%s%lu", prefix, (unsigned long)i + 1);
+				prefix = ",";
+			}
+
+		putchar('\n');
+	}
+
+	fflush(stdout);
+
+	return ret;
+
+error:
+	return -1;
+}
+
 static int debug_fd;
 
 void kvm_cpu__set_debug_fd(int fd)
@@ -156,8 +263,10 @@ struct kvm_cpu *kvm_cpu__arch_init(struct kvm *kvm, unsigned long cpu_id)
 	if (err || target->init(vcpu))
 		die("Unable to initialise vcpu");
 
-	if (kvm->cfg.arch.show_reg_list)
+	if (kvm->cfg.arch.show_reg_list) {
+		kvm_show_sve_info(vcpu);
 		kvm_show_reg_list(vcpu);
+	}
 
 	coalesced_offset = ioctl(kvm->sys_fd, KVM_CHECK_EXTENSION,
 				 KVM_CAP_COALESCED_MMIO);
-- 
2.1.4


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