KVM: arm64/sve: Add SVE support to register access ioctl interface

This patch adds the following registers for access via the
KVM_{GET,SET}_ONE_REG interface:

 * KVM_REG_ARM64_SVE_ZREG(n, i) (n = 0..31) (in 2048-bit slices)
 * KVM_REG_ARM64_SVE_PREG(n, i) (n = 0..15) (in 256-bit slices)
 * KVM_REG_ARM64_SVE_FFR(i) (in 256-bit slices)

In order to adapt gracefully to future architectural extensions,
the registers are logically divided up into slices as noted above:
the i parameter denotes the slice index.

This allows us to reserve space in the ABI for future expansion of
these registers.  However, as of today the architecture does not
permit registers to be larger than a single slice, so no code is
needed in the kernel to expose additional slices, for now.  The
code can be extended later as needed to expose them up to a maximum
of 32 slices (as carved out in the architecture itself) if they
really exist someday.

The registers are only visible for vcpus that have SVE enabled.
They are not enumerated by KVM_GET_REG_LIST on vcpus that do not
have SVE.

Accesses to the FPSIMD registers via KVM_REG_ARM_CORE is not
allowed for SVE-enabled vcpus: SVE-aware userspace can use the
KVM_REG_ARM64_SVE_ZREG() interface instead to access the same
register state.  This avoids some complex and pointless emulation
in the kernel to convert between the two views of these aliased
registers.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Tested-by: zhang.lei <zhang.lei@jp.fujitsu.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

1 files changed, 127 insertions, 12 deletions

diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 756d0d614993..736d8cb8dad7 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -19,8 +19,11 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/bits.h>
 #include <linux/errno.h>
 #include <linux/err.h>
+#include <linux/nospec.h>
+#include <linux/kernel.h>
 #include <linux/kvm_host.h>
 #include <linux/module.h>
 #include <linux/stddef.h>
@@ -30,9 +33,12 @@
 #include <kvm/arm_psci.h>
 #include <asm/cputype.h>
 #include <linux/uaccess.h>
+#include <asm/fpsimd.h>
 #include <asm/kvm.h>
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_coproc.h>
+#include <asm/kvm_host.h>
+#include <asm/sigcontext.h>
 
 #include "trace.h"
 
@@ -200,6 +206,115 @@ out:
 	return err;
 }
 
+#define SVE_REG_SLICE_SHIFT	0
+#define SVE_REG_SLICE_BITS	5
+#define SVE_REG_ID_SHIFT	(SVE_REG_SLICE_SHIFT + SVE_REG_SLICE_BITS)
+#define SVE_REG_ID_BITS		5
+
+#define SVE_REG_SLICE_MASK					\
+	GENMASK(SVE_REG_SLICE_SHIFT + SVE_REG_SLICE_BITS - 1,	\
+		SVE_REG_SLICE_SHIFT)
+#define SVE_REG_ID_MASK							\
+	GENMASK(SVE_REG_ID_SHIFT + SVE_REG_ID_BITS - 1, SVE_REG_ID_SHIFT)
+
+#define SVE_NUM_SLICES (1 << SVE_REG_SLICE_BITS)
+
+#define KVM_SVE_ZREG_SIZE KVM_REG_SIZE(KVM_REG_ARM64_SVE_ZREG(0, 0))
+#define KVM_SVE_PREG_SIZE KVM_REG_SIZE(KVM_REG_ARM64_SVE_PREG(0, 0))
+
+/* Bounds of a single SVE register slice within vcpu->arch.sve_state */
+struct sve_state_reg_region {
+	unsigned int koffset;	/* offset into sve_state in kernel memory */
+	unsigned int klen;	/* length in kernel memory */
+	unsigned int upad;	/* extra trailing padding in user memory */
+};
+
+/* Get sanitised bounds for user/kernel SVE register copy */
+static int sve_reg_to_region(struct sve_state_reg_region *region,
+			     struct kvm_vcpu *vcpu,
+			     const struct kvm_one_reg *reg)
+{
+	/* reg ID ranges for Z- registers */
+	const u64 zreg_id_min = KVM_REG_ARM64_SVE_ZREG(0, 0);
+	const u64 zreg_id_max = KVM_REG_ARM64_SVE_ZREG(SVE_NUM_ZREGS - 1,
+						       SVE_NUM_SLICES - 1);
+
+	/* reg ID ranges for P- registers and FFR (which are contiguous) */
+	const u64 preg_id_min = KVM_REG_ARM64_SVE_PREG(0, 0);
+	const u64 preg_id_max = KVM_REG_ARM64_SVE_FFR(SVE_NUM_SLICES - 1);
+
+	unsigned int vq;
+	unsigned int reg_num;
+
+	unsigned int reqoffset, reqlen; /* User-requested offset and length */
+	unsigned int maxlen; /* Maxmimum permitted length */
+
+	size_t sve_state_size;
+
+	/* Only the first slice ever exists, for now: */
+	if ((reg->id & SVE_REG_SLICE_MASK) != 0)
+		return -ENOENT;
+
+	vq = sve_vq_from_vl(vcpu->arch.sve_max_vl);
+
+	reg_num = (reg->id & SVE_REG_ID_MASK) >> SVE_REG_ID_SHIFT;
+
+	if (reg->id >= zreg_id_min && reg->id <= zreg_id_max) {
+		reqoffset = SVE_SIG_ZREG_OFFSET(vq, reg_num) -
+				SVE_SIG_REGS_OFFSET;
+		reqlen = KVM_SVE_ZREG_SIZE;
+		maxlen = SVE_SIG_ZREG_SIZE(vq);
+	} else if (reg->id >= preg_id_min && reg->id <= preg_id_max) {
+		reqoffset = SVE_SIG_PREG_OFFSET(vq, reg_num) -
+				SVE_SIG_REGS_OFFSET;
+		reqlen = KVM_SVE_PREG_SIZE;
+		maxlen = SVE_SIG_PREG_SIZE(vq);
+	} else {
+		return -ENOENT;
+	}
+
+	sve_state_size = vcpu_sve_state_size(vcpu);
+	if (!sve_state_size)
+		return -EINVAL;
+
+	region->koffset = array_index_nospec(reqoffset, sve_state_size);
+	region->klen = min(maxlen, reqlen);
+	region->upad = reqlen - region->klen;
+
+	return 0;
+}
+
+static int get_sve_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
+{
+	struct sve_state_reg_region region;
+	char __user *uptr = (char __user *)reg->addr;
+
+	if (!vcpu_has_sve(vcpu) || sve_reg_to_region(&region, vcpu, reg))
+		return -ENOENT;
+
+	if (copy_to_user(uptr, vcpu->arch.sve_state + region.koffset,
+			 region.klen) ||
+	    clear_user(uptr + region.klen, region.upad))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int set_sve_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
+{
+	struct sve_state_reg_region region;
+	const char __user *uptr = (const char __user *)reg->addr;
+
+	if (!vcpu_has_sve(vcpu) || sve_reg_to_region(&region, vcpu, reg))
+		return -ENOENT;
+
+	if (copy_from_user(vcpu->arch.sve_state + region.koffset, uptr,
+			   region.klen))
+		return -EFAULT;
+
+	return 0;
+}
+
 int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
 {
 	return -EINVAL;
@@ -346,12 +461,12 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	if ((reg->id & ~KVM_REG_SIZE_MASK) >> 32 != KVM_REG_ARM64 >> 32)
 		return -EINVAL;
 
-	/* Register group 16 means we want a core register. */
-	if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
-		return get_core_reg(vcpu, reg);
-
-	if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_FW)
-		return kvm_arm_get_fw_reg(vcpu, reg);
+	switch (reg->id & KVM_REG_ARM_COPROC_MASK) {
+	case KVM_REG_ARM_CORE:	return get_core_reg(vcpu, reg);
+	case KVM_REG_ARM_FW:	return kvm_arm_get_fw_reg(vcpu, reg);
+	case KVM_REG_ARM64_SVE:	return get_sve_reg(vcpu, reg);
+	default: break; /* fall through */
+	}
 
 	if (is_timer_reg(reg->id))
 		return get_timer_reg(vcpu, reg);
@@ -365,12 +480,12 @@ int kvm_arm_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	if ((reg->id & ~KVM_REG_SIZE_MASK) >> 32 != KVM_REG_ARM64 >> 32)
 		return -EINVAL;
 
-	/* Register group 16 means we set a core register. */
-	if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
-		return set_core_reg(vcpu, reg);
-
-	if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_FW)
-		return kvm_arm_set_fw_reg(vcpu, reg);
+	switch (reg->id & KVM_REG_ARM_COPROC_MASK) {
+	case KVM_REG_ARM_CORE:	return set_core_reg(vcpu, reg);
+	case KVM_REG_ARM_FW:	return kvm_arm_set_fw_reg(vcpu, reg);
+	case KVM_REG_ARM64_SVE:	return set_sve_reg(vcpu, reg);
+	default: break; /* fall through */
+	}
 
 	if (is_timer_reg(reg->id))
 		return set_timer_reg(vcpu, reg);