Commit 56d77aa8 authored by Oliver Upton's avatar Oliver Upton
Browse files

KVM: arm64: Allow userspace to change ID_AA64ISAR{0-2}_EL1 



Almost all of the features described by the ISA registers have no KVM
involvement. Allow userspace to change the value of these registers with
a couple exceptions:

 - MOPS is not writable as KVM does not currently virtualize FEAT_MOPS.

 - The PAuth fields are not writable as KVM requires both address and
   generic authentication be enabled.

Co-developed-by: default avatarJing Zhang <jingzhangos@google.com>
Signed-off-by: default avatarJing Zhang <jingzhangos@google.com>
Reviewed-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231003230408.3405722-7-oliver.upton@linux.dev


Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent 9f9917bc

arch/arm64/kvm/sys_regs.c

+26 −12
Original line number Diff line number Diff line
@@ -1851,11 +1851,14 @@ static unsigned int elx2_visibility(const struct kvm_vcpu *vcpu, 
 * from userspace.

 */



/* sys_reg_desc initialiser for known cpufeature ID registers */

#define ID_SANITISED(name) {			\

#define ID_DESC(name)				\

	SYS_DESC(SYS_##name),			\

	.access	= access_id_reg,		\

	.get_user = get_id_reg,			\

	.get_user = get_id_reg			\



/* sys_reg_desc initialiser for known cpufeature ID registers */

#define ID_SANITISED(name) {			\

	ID_DESC(name),				\

	.set_user = set_id_reg,			\

	.visibility = id_visibility,		\

	.reset = kvm_read_sanitised_id_reg,	\
@@ -1864,15 +1867,22 @@ static unsigned int elx2_visibility(const struct kvm_vcpu *vcpu, 


/* sys_reg_desc initialiser for known cpufeature ID registers */

#define AA32_ID_SANITISED(name) {		\

	SYS_DESC(SYS_##name),			\

	.access	= access_id_reg,		\

	.get_user = get_id_reg,			\

	ID_DESC(name),				\

	.set_user = set_id_reg,			\

	.visibility = aa32_id_visibility,	\

	.reset = kvm_read_sanitised_id_reg,	\

	.val = 0,				\

}



/* sys_reg_desc initialiser for writable ID registers */

#define ID_WRITABLE(name, mask) {		\

	ID_DESC(name),				\

	.set_user = set_id_reg,			\

	.visibility = id_visibility,		\

	.reset = kvm_read_sanitised_id_reg,	\

	.val = mask,				\

}



/*

 * sys_reg_desc initialiser for architecturally unallocated cpufeature ID

 * register with encoding Op0=3, Op1=0, CRn=0, CRm=crm, Op2=op2
@@ -1894,9 +1904,7 @@ static unsigned int elx2_visibility(const struct kvm_vcpu *vcpu, 
 * RAZ for the guest.

 */

#define ID_HIDDEN(name) {			\

	SYS_DESC(SYS_##name),			\

	.access = access_id_reg,		\

	.get_user = get_id_reg,			\

	ID_DESC(name),				\

	.set_user = set_id_reg,			\

	.visibility = raz_visibility,		\

	.reset = kvm_read_sanitised_id_reg,	\
@@ -2075,9 +2083,15 @@ static const struct sys_reg_desc sys_reg_descs[] = { 
	ID_UNALLOCATED(5,7),



	/* CRm=6 */

	ID_SANITISED(ID_AA64ISAR0_EL1),

	ID_SANITISED(ID_AA64ISAR1_EL1),

	ID_SANITISED(ID_AA64ISAR2_EL1),

	ID_WRITABLE(ID_AA64ISAR0_EL1, ~ID_AA64ISAR0_EL1_RES0),

	ID_WRITABLE(ID_AA64ISAR1_EL1, ~(ID_AA64ISAR1_EL1_GPI |

					ID_AA64ISAR1_EL1_GPA |

					ID_AA64ISAR1_EL1_API |

					ID_AA64ISAR1_EL1_APA)),

	ID_WRITABLE(ID_AA64ISAR2_EL1, ~(ID_AA64ISAR2_EL1_RES0 |

					ID_AA64ISAR2_EL1_MOPS |

					ID_AA64ISAR2_EL1_APA3 |

					ID_AA64ISAR2_EL1_GPA3)),

	ID_UNALLOCATED(6,3),

	ID_UNALLOCATED(6,4),

	ID_UNALLOCATED(6,5),