From 02949f36bc7b723944bf754b71cfdf75e5e36f44 Mon Sep 17 00:00:00 2001 From: Quentin Perret Date: Tue, 23 Apr 2024 16:05:14 +0100 Subject: [PATCH] KVM: arm64: Avoid BUG-ing from the host abort path Under certain circumstances __get_fault_info() may resolve the faulting address using the AT instruction. Given that this is being done outside of the host lock critical section, it is racy and the resolution via AT may fail. We currently BUG() in this situation, which is obviously less than ideal. Moving the address resolution to the critical section may have a performance impact, so let's keep it where it is, but bail out and return to the host to try a second time. Signed-off-by: Quentin Perret Signed-off-by: Fuad Tabba Acked-by: Oliver Upton Link: https://lore.kernel.org/r/20240423150538.2103045-7-tabba@google.com Signed-off-by: Marc Zyngier --- arch/arm64/kvm/hyp/nvhe/mem_protect.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 861c76021a250..caba3e4bd09e8 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -533,7 +533,13 @@ void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt) int ret = 0; esr = read_sysreg_el2(SYS_ESR); - BUG_ON(!__get_fault_info(esr, &fault)); + if (!__get_fault_info(esr, &fault)) { + /* + * We've presumably raced with a page-table change which caused + * AT to fail, try again. + */ + return; + } addr = (fault.hpfar_el2 & HPFAR_MASK) << 8; ret = host_stage2_idmap(addr); -- 2.30.2