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KVM: arm64: Don't evaluate HCR_EL2.NV nor HFGITR_EL2.ERET on ERET fast path

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We currently avoid using the ERET fast path if the guest has HCR_EL2.NV
set. This is an odd check, as NV doesn't mean much if HCR_EL2.TGE==1.

Similarly, evaluating HFGITR_EL2.ERET makes little sense, as
this only applies to the nested context, while the ERET fast-path
is purely for the benefit of L1.

Replace these bizarre checks with is_nested_ctxt() which makes a lot
more sense: if we are running an L2, the ERET trap must go to L1.

Fixes: dd0717a998 ("KVM: arm64: nv: Fast-track 'InHost' exception returns")
Reviewed-by: Yuan Yao <yaoyuan@linux.alibaba.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://patch.msgid.link/20260730071022.296811-8-maz@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>
This commit is contained in:
Marc Zyngier 2026-07-30 08:10:00 +01:00 committed by Oliver Upton
parent 0b72c40600
commit c938c826c1
1 changed files with 7 additions and 5 deletions
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12
arch/arm64/kvm/hyp/vhe/switch.c
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@ -344,13 +344,15 @@ static bool kvm_hyp_handle_eret(struct kvm_vcpu *vcpu, u64 *exit_code)
* if this is a VHE guest hypervisor returning to its own
* userspace, or the hypervisor performing a local exception
* return. No need to save/restore registers, no need to
* switch S2 MMU. Just do the canonical ERET.
* switch S2 MMU. Just do the canonical ERET unless we are in
* nested context.
*
* Unless the trap has to be forwarded further down the line,
* of course...
* Note that this is made possible because KVM itself never traps
* ERET when running an L2. The consequence is that any ERET trap is
* the result of HCR_EL2 or HFGITR_EL2 programming by L1 for its own
* guest, and the exception must be forwarded to L1.
*/
if ((__vcpu_sys_reg(vcpu, HCR_EL2) & HCR_NV) ||
(__vcpu_sys_reg(vcpu, HFGITR_EL2) & HFGITR_EL2_ERET))
if (is_nested_ctxt(vcpu))
return false;
spsr = read_sysreg_el1(SYS_SPSR);