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KVM: arm64: Avoid mismatched accesses to 'struct kvm_nvhe_init_params'

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When running with hVHE enabled, ___kvm_hyp_init() calls
__kvm_init_el2_state() on the CPU initialisation path during onlining
and resume from suspend.

In order to avoid clobbering the link register across this call, it is
stashed away in the 'tmp' member of 'struct kvm_nvhe_init_params',
however this save/restore operation is performed with the stage-1 MMU
disabled at EL2 and therefore gives rise to coherency problems because
the field is not aligned or padded to the CWG. For example, a cacheable
write to a physically-adjacent structure sharing the same cacheline
could lead to an eviction and subsequent write-back, overwriting the
saved LR while the incoming CPU is executing __kvm_init_el2_state().

Save the lr in far_el2 and remove the 'tmp' member from
'struct kvm_nvhe_init_params' altogether.

Cc: Oliver Upton <oupton@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Fixes: afa9b48f32 ("KVM: arm64: Shave a few bytes from the EL2 idmap code")
Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://patch.msgid.link/20260813131717.5885-1-will@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>
This commit is contained in:
Will Deacon 2026-08-13 14:17:16 +01:00 committed by Oliver Upton
parent a342faadc5
commit 028d8df0a1
3 changed files with 7 additions and 6 deletions
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1
arch/arm64/include/asm/kvm_asm.h
View File

@ -214,7 +214,6 @@ struct kvm_nvhe_init_params {
unsigned long hcr_el2;
unsigned long vttbr;
unsigned long vtcr;
unsigned long tmp;
};
/*

1
arch/arm64/kernel/asm-offsets.c
View File

@ -124,7 +124,6 @@ int main(void)
DEFINE(NVHE_INIT_HCR_EL2, offsetof(struct kvm_nvhe_init_params, hcr_el2));
DEFINE(NVHE_INIT_VTTBR, offsetof(struct kvm_nvhe_init_params, vttbr));
DEFINE(NVHE_INIT_VTCR, offsetof(struct kvm_nvhe_init_params, vtcr));
DEFINE(NVHE_INIT_TMP, offsetof(struct kvm_nvhe_init_params, tmp));
#endif
#ifdef CONFIG_CPU_PM
DEFINE(CPU_CTX_SP, offsetof(struct cpu_suspend_ctx, sp));

11
arch/arm64/kvm/hyp/nvhe/hyp-init.S
View File

@ -106,16 +106,19 @@ SYM_CODE_START_LOCAL(___kvm_hyp_init)
and x2, x1, x2
cbz x2, 1f
// hVHE: Replay the EL2 setup to account for the E2H bit
// TPIDR_EL2 is used to preserve x0 across the macro maze...
/*
* hVHE: Replay the EL2 setup to account for the E2H bit
* TPIDR_EL2 and FAR_EL2 are used to preserve x0 and LR across
* the macro maze...
*/
isb
msr tpidr_el2, x0
str lr, [x0, #NVHE_INIT_TMP]
msr far_el2, lr
bl __kvm_init_el2_state
mrs lr, far_el2
mrs x0, tpidr_el2
ldr lr, [x0, #NVHE_INIT_TMP]
1:
ldr x1, [x0, #NVHE_INIT_TPIDR_EL2]