arm64: Allow the user to select the max SVE vector length
Add a new flag, --sve-max-vl, which allows the user to specify an SVE
vector length for the VM. Just zero out unsupported VLs from what KVM
supports rather than cooking up the bitmap from scratch.
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240620165702.1134918-2-oliver.upton@linux.dev
Signed-off-by: Will Deacon <will@kernel.org>
diff --git a/arm/aarch64/include/kvm/kvm-config-arch.h b/arm/aarch64/include/kvm/kvm-config-arch.h
index eae8080..642fe67 100644
--- a/arm/aarch64/include/kvm/kvm-config-arch.h
+++ b/arm/aarch64/include/kvm/kvm-config-arch.h
@@ -2,6 +2,7 @@
#define KVM__KVM_CONFIG_ARCH_H
int vcpu_affinity_parser(const struct option *opt, const char *arg, int unset);
+int sve_vl_parser(const struct option *opt, const char *arg, int unset);
#define ARM_OPT_ARCH_RUN(cfg) \
OPT_BOOLEAN('\0', "aarch32", &(cfg)->aarch32_guest, \
@@ -19,7 +20,10 @@
"Specify random seed for Kernel Address Space " \
"Layout Randomization (KASLR)"), \
OPT_BOOLEAN('\0', "no-pvtime", &(cfg)->no_pvtime, "Disable" \
- " stolen time"),
+ " stolen time"), \
+ OPT_CALLBACK('\0', "sve-max-vl", NULL, "vector length", \
+ "Specify the max SVE vector length (in bits) for " \
+ "all vCPUs", sve_vl_parser, kvm),
#include "arm-common/kvm-config-arch.h"
#endif /* KVM__KVM_CONFIG_ARCH_H */
diff --git a/arm/aarch64/kvm-cpu.c b/arm/aarch64/kvm-cpu.c
index c8be10b..7b6061a 100644
--- a/arm/aarch64/kvm-cpu.c
+++ b/arm/aarch64/kvm-cpu.c
@@ -3,6 +3,7 @@
#include "kvm/virtio.h"
#include <asm/ptrace.h>
+#include <linux/bitops.h>
#define COMPAT_PSR_F_BIT 0x00000040
#define COMPAT_PSR_I_BIT 0x00000080
@@ -154,16 +155,66 @@
init->features[0] |= 1UL << KVM_ARM_VCPU_SVE;
}
+int sve_vl_parser(const struct option *opt, const char *arg, int unset)
+{
+ struct kvm *kvm = opt->ptr;
+ unsigned long val;
+ unsigned int vq;
+
+ errno = 0;
+ val = strtoull(arg, NULL, 10);
+ if (errno == ERANGE)
+ die("SVE vector length too large: %s", arg);
+
+ if (!val || (val & (val - 1)))
+ die("SVE vector length isn't power of 2: %s", arg);
+
+ vq = val / 128;
+ if (vq > KVM_ARM64_SVE_VQ_MAX || vq < KVM_ARM64_SVE_VQ_MIN)
+ die("SVE vector length out of range: %s", arg);
+
+ kvm->cfg.arch.sve_max_vq = vq;
+ return 0;
+}
+
+static int vcpu_configure_sve(struct kvm_cpu *vcpu)
+{
+ unsigned int max_vq = vcpu->kvm->cfg.arch.sve_max_vq;
+ int feature = KVM_ARM_VCPU_SVE;
+
+ if (max_vq) {
+ unsigned long vls[KVM_ARM64_SVE_VLS_WORDS];
+ struct kvm_one_reg reg = {
+ .id = KVM_REG_ARM64_SVE_VLS,
+ .addr = (u64)&vls,
+ };
+ unsigned int vq;
+
+ if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®))
+ die_perror("KVM_GET_ONE_REG failed (KVM_ARM64_SVE_VLS)");
+
+ if (!test_bit(max_vq - KVM_ARM64_SVE_VQ_MIN, vls))
+ die("SVE vector length (%u) not supported", max_vq * 128);
+
+ for (vq = KVM_ARM64_SVE_VQ_MAX; vq > max_vq; vq--)
+ clear_bit(vq - KVM_ARM64_SVE_VQ_MIN, vls);
+
+ if (ioctl(vcpu->vcpu_fd, KVM_SET_ONE_REG, ®))
+ die_perror("KVM_SET_ONE_REG failed (KVM_ARM64_SVE_VLS)");
+ }
+
+ if (ioctl(vcpu->vcpu_fd, KVM_ARM_VCPU_FINALIZE, &feature)) {
+ pr_err("KVM_ARM_VCPU_FINALIZE: %s", strerror(errno));
+ return -1;
+ }
+
+ return 0;
+}
+
int kvm_cpu__configure_features(struct kvm_cpu *vcpu)
{
- if (kvm__supports_extension(vcpu->kvm, KVM_CAP_ARM_SVE)) {
- int feature = KVM_ARM_VCPU_SVE;
-
- if (ioctl(vcpu->vcpu_fd, KVM_ARM_VCPU_FINALIZE, &feature)) {
- pr_err("KVM_ARM_VCPU_FINALIZE: %s", strerror(errno));
- return -1;
- }
- }
+ if (kvm__supports_extension(vcpu->kvm, KVM_CAP_ARM_SVE))
+ return vcpu_configure_sve(vcpu);
return 0;
}
diff --git a/arm/include/arm-common/kvm-config-arch.h b/arm/include/arm-common/kvm-config-arch.h
index 23a7486..4722d8f 100644
--- a/arm/include/arm-common/kvm-config-arch.h
+++ b/arm/include/arm-common/kvm-config-arch.h
@@ -13,7 +13,8 @@
u64 kaslr_seed;
enum irqchip_type irqchip;
u64 fw_addr;
- bool no_pvtime;
+ unsigned int sve_max_vq;
+ bool no_pvtime;
};
int irqchip_parser(const struct option *opt, const char *arg, int unset);
