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KVM: arm64: Get rid of HCRX_GUEST_FLAGS

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HCRX_GUEST_FLAGS gives random KVM hackers the impression that
they can stuff bits in this macro and unconditionally enable
features in the guest.

In general, this is wrong (we have been there with FEAT_MOPS,
and again with FEAT_TCRX).

Document that HCRX_EL2.SMPME is an exception rather than the rule,
and get rid of HCRX_GUEST_FLAGS.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/20240625130042.259175-3-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Marc Zyngier 2024-06-25 14:00:38 +01:00 committed by Oliver Upton
parent 9b58e665d6
commit a3ee9ce88b
2 changed files with 7 additions and 2 deletions
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1
arch/arm64/include/asm/kvm_arm.h
View File

@ -102,7 +102,6 @@
#define HCR_HOST_NVHE_PROTECTED_FLAGS (HCR_HOST_NVHE_FLAGS | HCR_TSC)
#define HCR_HOST_VHE_FLAGS (HCR_RW | HCR_TGE | HCR_E2H)
#define HCRX_GUEST_FLAGS (HCRX_EL2_SMPME)
#define HCRX_HOST_FLAGS (HCRX_EL2_MSCEn | HCRX_EL2_TCR2En | HCRX_EL2_EnFPM)
/* TCR_EL2 Registers bits */

8
arch/arm64/kvm/sys_regs.c
View File

@ -4062,7 +4062,13 @@ void kvm_init_sysreg(struct kvm_vcpu *vcpu)
vcpu->arch.hcr_el2 |= HCR_TTLBOS;
if (cpus_have_final_cap(ARM64_HAS_HCX)) {
vcpu->arch.hcrx_el2 = HCRX_GUEST_FLAGS;
/*
* In general, all HCRX_EL2 bits are gated by a feature.
* The only reason we can set SMPME without checking any
* feature is that its effects are not directly observable
* from the guest.
*/
vcpu->arch.hcrx_el2 = HCRX_EL2_SMPME;
if (kvm_has_feat(kvm, ID_AA64ISAR2_EL1, MOPS, IMP))
vcpu->arch.hcrx_el2 |= (HCRX_EL2_MSCEn | HCRX_EL2_MCE2);