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KVM: arm64: Flush external_mdscr_el1 to the pKVM hyp vCPU

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flush_debug_state() propagates the guest's debug_owner and the
owner-selected debug register state to the hyp vCPU, but not
external_mdscr_el1. While the host owns the debug registers, the world
switch loads MDSCR_EL1 from external_mdscr_el1 (ctxt_mdscr_el1()),
where the host's KDE/MDE/SS bits live. A non-protected guest under
KVM_GUESTDBG_USE_HW or single-step therefore runs with MDSCR_EL1.MDE/SS
clear in hardware, and its watchpoints, breakpoints and single-step
never fire.

Propagate external_mdscr_el1 to the hyp vCPU alongside the host-owned
debug state.

Fixes: 4ad3a0b87f ("KVM: arm64: Don't hijack guest context MDSCR_EL1")
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20260726143643.303456-2-fuad.tabba@linux.dev
Signed-off-by: Oliver Upton <oupton@kernel.org>
This commit is contained in:
Fuad Tabba 2026-07-26 15:36:42 +01:00 committed by Oliver Upton
parent 81b2d03f8c
commit 119a9a23fb
1 changed files with 8 additions and 2 deletions
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10
arch/arm64/kvm/hyp/nvhe/hyp-main.c
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@ -108,10 +108,16 @@ static void flush_debug_state(struct pkvm_hyp_vcpu *hyp_vcpu)
hyp_vcpu->vcpu.arch.debug_owner = host_vcpu->arch.debug_owner;
if (kvm_guest_owns_debug_regs(&hyp_vcpu->vcpu))
if (kvm_guest_owns_debug_regs(&hyp_vcpu->vcpu)) {
hyp_vcpu->vcpu.arch.vcpu_debug_state = host_vcpu->arch.vcpu_debug_state;
else if (kvm_host_owns_debug_regs(&hyp_vcpu->vcpu))
} else if (kvm_host_owns_debug_regs(&hyp_vcpu->vcpu)) {
hyp_vcpu->vcpu.arch.external_debug_state = host_vcpu->arch.external_debug_state;
/*
* The world switch loads MDSCR_EL1 from external_mdscr_el1
* (ctxt_mdscr_el1()).
*/
hyp_vcpu->vcpu.arch.external_mdscr_el1 = host_vcpu->arch.external_mdscr_el1;
}
}
static void sync_debug_state(struct pkvm_hyp_vcpu *hyp_vcpu)