From 363de99b770500b2102e9375249726254fdeae8a Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Tue, 6 Aug 2019 16:57:37 +0100 Subject: [PATCH] arm64/kvm: Remove VMID rollover I-cache maintenance For VPIPT I-caches, we need I-cache maintenance on VMID rollover to avoid an ABA problem. Consider a single vCPU VM, with a pinned stage-2, running with an idmap VA->IPA and idmap IPA->PA. If we don't do maintenance on rollover: // VMID A Writes insn X to PA 0xF Invalidates PA 0xF (for VMID A) I$ contains [{A,F}->X] [VMID ROLLOVER] // VMID B Writes insn Y to PA 0xF Invalidates PA 0xF (for VMID B) I$ contains [{A,F}->X, {B,F}->Y] [VMID ROLLOVER] // VMID A I$ contains [{A,F}->X, {B,F}->Y] Unexpectedly hits stale I$ line {A,F}->X. However, for PIPT and VIPT I-caches, the VMID doesn't affect lookup or constrain maintenance. Given the VMID doesn't affect PIPT and VIPT I-caches, and given VMID rollover is independent of changes to stage-2 mappings, I-cache maintenance cannot be necessary on VMID rollover for PIPT or VIPT I-caches. This patch removes the maintenance on rollover for VIPT and PIPT I-caches. At the same time, the unnecessary colons are removed from the asm statement to make it more legible. Signed-off-by: Mark Rutland Cc: Christoffer Dall Reviewed-by: James Morse Cc: Julien Thierry Cc: Suzuki K Poulose Cc: kvmarm@lists.cs.columbia.edu Signed-off-by: Marc Zyngier --- arch/arm64/kvm/hyp/tlb.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hyp/tlb.c b/arch/arm64/kvm/hyp/tlb.c index d49a144..c466060 100644 --- a/arch/arm64/kvm/hyp/tlb.c +++ b/arch/arm64/kvm/hyp/tlb.c @@ -193,6 +193,18 @@ void __hyp_text __kvm_flush_vm_context(void) { dsb(ishst); __tlbi(alle1is); - asm volatile("ic ialluis" : : ); + + /* + * VIPT and PIPT caches are not affected by VMID, so no maintenance + * is necessary across a VMID rollover. + * + * VPIPT caches constrain lookup and maintenance to the active VMID, + * so we need to invalidate lines with a stale VMID to avoid an ABA + * race after multiple rollovers. + * + */ + if (icache_is_vpipt()) + asm volatile("ic ialluis"); + dsb(ish); } -- 2.7.4