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authorMark Rutland <mark.rutland@arm.com>2019-08-06 18:57:37 +0300
committerMarc Zyngier <maz@kernel.org>2019-08-18 20:41:12 +0300
commit363de99b770500b2102e9375249726254fdeae8a (patch)
tree0aa87afbf97e2ce3bf5e69199639d05f4e5490c4 /arch
parent41108170d98069b34837c4512f93ef2ce651b812 (diff)
downloadlinux-363de99b770500b2102e9375249726254fdeae8a.tar.xz
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 <mark.rutland@arm.com> Cc: Christoffer Dall <christoffer.dall@arm.com> Reviewed-by: James Morse <james.morse@arm.com> Cc: Julien Thierry <julien.thierry.kdev@gmail.com> Cc: Suzuki K Poulose <suzuki.poulose@arm.com> Cc: kvmarm@lists.cs.columbia.edu Signed-off-by: Marc Zyngier <maz@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/kvm/hyp/tlb.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/arch/arm64/kvm/hyp/tlb.c b/arch/arm64/kvm/hyp/tlb.c
index d49a14497715..c466060b76d6 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);
}