Commit 52110aa9 authored by Dave Martin's avatar Dave Martin Committed by Marc Zyngier
Browse files

KVM: arm64/sve: Make register ioctl access errors more consistent 



Currently, the way error codes are generated when processing the
SVE register access ioctls in a bit haphazard.

This patch refactors the code so that the behaviour is more
consistent: now, -EINVAL should be returned only for unrecognised
register IDs or when some other runtime error occurs.  -ENOENT is
returned for register IDs that are recognised, but whose
corresponding register (or slice) does not exist for the vcpu.

To this end, in {get,set}_sve_reg() we now delegate the
vcpu_has_sve() check down into {get,set}_sve_vls() and
sve_reg_to_region().  The KVM_REG_ARM64_SVE_VLS special case is
picked off first, then sve_reg_to_region() plays the role of
exhaustively validating or rejecting the register ID and (where
accepted) computing the applicable register region as before.

sve_reg_to_region() is rearranged so that -ENOENT or -EPERM is not
returned prematurely, before checking whether reg->id is in a
recognised range.

-EPERM is now only returned when an attempt is made to access an
actually existing register slice on an unfinalized vcpu.

Fixes: e1c9c983 ("KVM: arm64/sve: Add SVE support to register access ioctl interface")
Fixes: 9033bba4 ("KVM: arm64/sve: Add pseudo-register for the guest's vector lengths")
Suggested-by: default avatarAndrew Jones <drjones@redhat.com>
Signed-off-by: default avatarDave Martin <Dave.Martin@arm.com>
Reviewed-by: default avatarAndrew Jones <drjones@redhat.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
parent f8d4635a

arch/arm64/kvm/guest.c

+31 −21
Original line number Diff line number Diff line
@@ -221,6 +221,9 @@ static int get_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg) 
	unsigned int max_vq, vq;

	u64 vqs[DIV_ROUND_UP(SVE_VQ_MAX - SVE_VQ_MIN + 1, 64)];



	if (!vcpu_has_sve(vcpu))

		return -ENOENT;



	if (WARN_ON(!sve_vl_valid(vcpu->arch.sve_max_vl)))

		return -EINVAL;
@@ -242,6 +245,9 @@ static int set_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg) 
	unsigned int max_vq, vq;

	u64 vqs[DIV_ROUND_UP(SVE_VQ_MAX - SVE_VQ_MIN + 1, 64)];



	if (!vcpu_has_sve(vcpu))

		return -ENOENT;



	if (kvm_arm_vcpu_sve_finalized(vcpu))

		return -EPERM; /* too late! */
@@ -304,7 +310,10 @@ struct sve_state_reg_region { 
	unsigned int upad;	/* extra trailing padding in user memory */

};



/* Get sanitised bounds for user/kernel SVE register copy */

/*

 * Validate SVE register ID and 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)
@@ -335,25 +344,30 @@ static int sve_reg_to_region(struct sve_state_reg_region *region, 
	/* Verify that we match the UAPI header: */

	BUILD_BUG_ON(SVE_NUM_SLICES != KVM_ARM64_SVE_MAX_SLICES);



	if ((reg->id & SVE_REG_SLICE_MASK) > 0)

	reg_num = (reg->id & SVE_REG_ID_MASK) >> SVE_REG_ID_SHIFT;



	if (reg->id >= zreg_id_min && reg->id <= zreg_id_max) {

		if (!vcpu_has_sve(vcpu) || (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) {

		if (!vcpu_has_sve(vcpu) || (reg->id & SVE_REG_SLICE_MASK) > 0)

			return -ENOENT;



		vq = sve_vq_from_vl(vcpu->arch.sve_max_vl);



		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;

		return -EINVAL;

	}



	sve_state_size = vcpu_sve_state_size(vcpu);
@@ -369,24 +383,22 @@ static int sve_reg_to_region(struct sve_state_reg_region *region, 


static int get_sve_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)

{

	int ret;

	struct sve_state_reg_region region;

	char __user *uptr = (char __user *)reg->addr;



	if (!vcpu_has_sve(vcpu))

		return -ENOENT;



	/* Handle the KVM_REG_ARM64_SVE_VLS pseudo-reg as a special case: */

	if (reg->id == KVM_REG_ARM64_SVE_VLS)

		return get_sve_vls(vcpu, reg);



	/* Otherwise, reg is an architectural SVE register... */

	/* Try to interpret reg ID as an architectural SVE register... */

	ret = sve_reg_to_region(&region, vcpu, reg);

	if (ret)

		return ret;



	if (!kvm_arm_vcpu_sve_finalized(vcpu))

		return -EPERM;



	if (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))
@@ -397,24 +409,22 @@ static int get_sve_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg) 


static int set_sve_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)

{

	int ret;

	struct sve_state_reg_region region;

	const char __user *uptr = (const char __user *)reg->addr;



	if (!vcpu_has_sve(vcpu))

		return -ENOENT;



	/* Handle the KVM_REG_ARM64_SVE_VLS pseudo-reg as a special case: */

	if (reg->id == KVM_REG_ARM64_SVE_VLS)

		return set_sve_vls(vcpu, reg);



	/* Otherwise, reg is an architectural SVE register... */

	/* Try to interpret reg ID as an architectural SVE register... */

	ret = sve_reg_to_region(&region, vcpu, reg);

	if (ret)

		return ret;



	if (!kvm_arm_vcpu_sve_finalized(vcpu))

		return -EPERM;



	if (sve_reg_to_region(&region, vcpu, reg))

		return -ENOENT;



	if (copy_from_user(vcpu->arch.sve_state + region.koffset, uptr,

			   region.klen))

		return -EFAULT;

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