Commit 2843cae2 authored by Sebastian Ott's avatar Sebastian Ott Committed by Oliver Upton
Browse files

KVM: arm64: Treat CTR_EL0 as a VM feature ID register 



CTR_EL0 is currently handled as an invariant register, thus
guests will be presented with the host value of that register.

Add emulation for CTR_EL0 based on a per VM value. Userspace can
switch off DIC and IDC bits and reduce DminLine and IminLine sizes.
Naturally, ensure CTR_EL0 is trapped (HCR_EL2.TID2=1) any time that a
VM's CTR_EL0 differs from hardware.

Signed-off-by: default avatarSebastian Ott <sebott@redhat.com>
Reviewed-by: default avatarShaoqin Huang <shahuang@redhat.com>
Link: https://lore.kernel.org/r/20240619174036.483943-8-oliver.upton@linux.dev


Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent f1ff3fc5

arch/arm64/include/asm/kvm_host.h

+4 −0
Original line number Diff line number Diff line
@@ -329,6 +329,8 @@ struct kvm_arch { 
#define KVM_ARM_ID_REG_NUM	(IDREG_IDX(sys_reg(3, 0, 0, 7, 7)) + 1)

	u64 id_regs[KVM_ARM_ID_REG_NUM];



	u64 ctr_el0;



	/* Masks for VNCR-baked sysregs */

	struct kvm_sysreg_masks	*sysreg_masks;
@@ -1335,6 +1337,8 @@ static inline u64 *__vm_id_reg(struct kvm_arch *ka, u32 reg) 
	switch (reg) {

	case sys_reg(3, 0, 0, 1, 0) ... sys_reg(3, 0, 0, 7, 7):

		return &ka->id_regs[IDREG_IDX(reg)];

	case SYS_CTR_EL0:

		return &ka->ctr_el0;

	default:

		WARN_ON_ONCE(1);

		return NULL;

arch/arm64/kvm/sys_regs.c

+10 −10
Original line number Diff line number Diff line
@@ -1583,6 +1583,9 @@ static bool is_feature_id_reg(u32 encoding) 
 */

static inline bool is_vm_ftr_id_reg(u32 id)

{

	if (id == SYS_CTR_EL0)

		return true;



	return (sys_reg_Op0(id) == 3 && sys_reg_Op1(id) == 0 &&

		sys_reg_CRn(id) == 0 && sys_reg_CRm(id) >= 1 &&

		sys_reg_CRm(id) < 8);
@@ -1898,7 +1901,7 @@ static bool access_ctr(struct kvm_vcpu *vcpu, struct sys_reg_params *p, 
	if (p->is_write)

		return write_to_read_only(vcpu, p, r);



	p->regval = read_sanitised_ftr_reg(SYS_CTR_EL0);

	p->regval = kvm_read_vm_id_reg(vcpu->kvm, SYS_CTR_EL0);

	return true;

}
@@ -2487,7 +2490,10 @@ static const struct sys_reg_desc sys_reg_descs[] = { 
	{ SYS_DESC(SYS_CCSIDR2_EL1), undef_access },

	{ SYS_DESC(SYS_SMIDR_EL1), undef_access },

	{ SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 },

	{ SYS_DESC(SYS_CTR_EL0), access_ctr },

	ID_WRITABLE(CTR_EL0, CTR_EL0_DIC_MASK |

			     CTR_EL0_IDC_MASK |

			     CTR_EL0_DminLine_MASK |

			     CTR_EL0_IminLine_MASK),

	{ SYS_DESC(SYS_SVCR), undef_access },



	{ PMU_SYS_REG(PMCR_EL0), .access = access_pmcr, .reset = reset_pmcr,
@@ -3725,18 +3731,11 @@ FUNCTION_INVARIANT(midr_el1) 
FUNCTION_INVARIANT(revidr_el1)

FUNCTION_INVARIANT(aidr_el1)



static u64 get_ctr_el0(struct kvm_vcpu *v, const struct sys_reg_desc *r)

{

	((struct sys_reg_desc *)r)->val = read_sanitised_ftr_reg(SYS_CTR_EL0);

	return ((struct sys_reg_desc *)r)->val;

}



/* ->val is filled in by kvm_sys_reg_table_init() */

static struct sys_reg_desc invariant_sys_regs[] __ro_after_init = {

	{ SYS_DESC(SYS_MIDR_EL1), NULL, get_midr_el1 },

	{ SYS_DESC(SYS_REVIDR_EL1), NULL, get_revidr_el1 },

	{ SYS_DESC(SYS_AIDR_EL1), NULL, get_aidr_el1 },

	{ SYS_DESC(SYS_CTR_EL0), NULL, get_ctr_el0 },

};



static int get_invariant_sys_reg(u64 id, u64 __user *uaddr)
@@ -4086,7 +4085,8 @@ static void vcpu_set_hcr(struct kvm_vcpu *vcpu) 
		vcpu->arch.hcr_el2 |= HCR_FWB;



	if (cpus_have_final_cap(ARM64_HAS_EVT) &&

	    !cpus_have_final_cap(ARM64_MISMATCHED_CACHE_TYPE))

	    !cpus_have_final_cap(ARM64_MISMATCHED_CACHE_TYPE) &&

	    kvm_read_vm_id_reg(kvm, SYS_CTR_EL0) == read_sanitised_ftr_reg(SYS_CTR_EL0))

		vcpu->arch.hcr_el2 |= HCR_TID4;

	else

		vcpu->arch.hcr_el2 |= HCR_TID2;