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KVM: arm64: Classify CPTR_EL2 as a SR_LOC_SPECIAL register

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It may not be obvious unless you look at it closely, but CPTR_EL2
is treated very differently from other registers. It is one the
registers that, despite looking very similar between EL1 and EL2
when E2H==1, have RES0 bits that get in the way.

Make it clear that CPTR_EL2 is odd by classifying it as SR_LOC_SPECIAL,
just like CNTHCTL_EL2 (and for the same reasons). This makes it
possible to use vcpu_read_sys_reg() with it, and will be necessary
once we support FEAT_NV2P1.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Reviewed-by: Yuan Yao <yaoyuan@linux.alibaba.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://patch.msgid.link/20260730071022.296811-7-maz@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>
This commit is contained in:
Marc Zyngier 2026-07-30 08:09:59 +01:00 committed by Oliver Upton
parent fed0a1e87c
commit 0b72c40600
2 changed files with 19 additions and 3 deletions
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2
arch/arm64/include/asm/kvm_emulate.h
View File

@ -617,7 +617,7 @@ static __always_inline void kvm_incr_pc(struct kvm_vcpu *vcpu)
*/
static inline u64 vcpu_sanitised_cptr_el2(const struct kvm_vcpu *vcpu)
{
u64 cptr = __vcpu_sys_reg(vcpu, CPTR_EL2);
u64 cptr = vcpu_read_sys_reg(vcpu, CPTR_EL2);
if (!vcpu_el2_e2h_is_set(vcpu))
cptr = translate_cptr_el2_to_cpacr_el1(cptr);

20
arch/arm64/kvm/sys_regs.c
View File

@ -183,8 +183,6 @@ static void locate_register(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg,
switch (reg) {
MAPPED_EL2_SYSREG(SCTLR_EL2, SCTLR_EL1,
translate_sctlr_el2_to_sctlr_el1 );
MAPPED_EL2_SYSREG(CPTR_EL2, CPACR_EL1,
translate_cptr_el2_to_cpacr_el1 );
MAPPED_EL2_SYSREG(TTBR0_EL2, TTBR0_EL1,
translate_ttbr0_el2_to_ttbr0_el1 );
MAPPED_EL2_SYSREG(TTBR1_EL2, TTBR1_EL1, NULL );
@ -210,6 +208,19 @@ static void locate_register(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg,
loc->loc = ((is_hyp_ctxt(vcpu) && vcpu_el2_e2h_is_set(vcpu)) ?
SR_LOC_SPECIAL : SR_LOC_MEMORY);
break;
case CPTR_EL2:
/*
* CPTR_EL2 is just as special, and needs a certain amount
* of handholding. It always lives in memory, due to being
* heavily trapped thanks to CPACR_EL1.TCPAC being RES0.
* FEAT_NV2p1 fixes this.
*/
locate_mapped_el2_register(vcpu, CPTR_EL2, CPACR_EL1,
translate_cptr_el2_to_cpacr_el1,
loc);
if (is_hyp_ctxt(vcpu) && vcpu_el2_e2h_is_set(vcpu))
loc->loc = SR_LOC_SPECIAL;
break;
default:
loc->loc = locate_direct_register(vcpu, reg);
}
@ -314,6 +325,8 @@ u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, enum vcpu_sysreg reg)
val &= CNTKCTL_VALID_BITS;
val |= __vcpu_sys_reg(vcpu, reg) & ~CNTKCTL_VALID_BITS;
return val;
case CPTR_EL2:
return __vcpu_sys_reg(vcpu, reg);
default:
WARN_ON_ONCE(1);
}
@ -359,6 +372,9 @@ void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, enum vcpu_sysreg reg)
*/
write_sysreg_el1(val, SYS_CNTKCTL);
break;
case CPTR_EL2:
write_sysreg_el1(val, SYS_CPACR);
break;
default:
WARN_ON_ONCE(1);
}