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author | Will Deacon <will.deacon@arm.com> | 2017-03-10 20:32:25 +0000 |
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committer | Catalin Marinas <catalin.marinas@arm.com> | 2017-03-20 16:25:45 +0000 |
commit | 87da236ebc711644dcff2339ee5b854f1abf1fca (patch) | |
tree | 73da290dd0092c7b537ee5c77476bd9d216bcf53 /arch/arm64/kvm | |
parent | dda288d7e4f605632dc6e19c69063f1725056208 (diff) | |
download | linux-stable-87da236ebc711644dcff2339ee5b854f1abf1fca.tar.gz linux-stable-87da236ebc711644dcff2339ee5b854f1abf1fca.tar.bz2 linux-stable-87da236ebc711644dcff2339ee5b854f1abf1fca.zip |
arm64: KVM: Add support for VPIPT I-caches
A VPIPT I-cache has two main properties:
1. Lines allocated into the cache are tagged by VMID and a lookup can
only hit lines that were allocated with the current VMID.
2. I-cache invalidation from EL1/0 only invalidates lines that match the
current VMID of the CPU doing the invalidation.
This can cause issues with non-VHE configurations, where the host runs
at EL1 and wants to invalidate I-cache entries for a guest running with
a different VMID. VHE is not affected, because the host runs at EL2 and
I-cache invalidation applies as expected.
This patch solves the problem by invalidating the I-cache when unmapping
a page at stage 2 on a system with a VPIPT I-cache but not running with
VHE enabled. Hopefully this is an obscure enough configuration that the
overhead isn't anything to worry about, although it does mean that the
by-range I-cache invalidation currently performed when mapping at stage
2 can be elided on such systems, because the I-cache will be clean for
the guest VMID following a rollover event.
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/kvm')
-rw-r--r-- | arch/arm64/kvm/hyp/tlb.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/arch/arm64/kvm/hyp/tlb.c b/arch/arm64/kvm/hyp/tlb.c index 9e1d2b75eecd..73464a96c365 100644 --- a/arch/arm64/kvm/hyp/tlb.c +++ b/arch/arm64/kvm/hyp/tlb.c @@ -94,6 +94,28 @@ void __hyp_text __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa) dsb(ish); isb(); + /* + * If the host is running at EL1 and we have a VPIPT I-cache, + * then we must perform I-cache maintenance at EL2 in order for + * it to have an effect on the guest. Since the guest cannot hit + * I-cache lines allocated with a different VMID, we don't need + * to worry about junk out of guest reset (we nuke the I-cache on + * VMID rollover), but we do need to be careful when remapping + * executable pages for the same guest. This can happen when KSM + * takes a CoW fault on an executable page, copies the page into + * a page that was previously mapped in the guest and then needs + * to invalidate the guest view of the I-cache for that page + * from EL1. To solve this, we invalidate the entire I-cache when + * unmapping a page from a guest if we have a VPIPT I-cache but + * the host is running at EL1. As above, we could do better if + * we had the VA. + * + * The moral of this story is: if you have a VPIPT I-cache, then + * you should be running with VHE enabled. + */ + if (!has_vhe() && icache_is_vpipt()) + __flush_icache_all(); + __tlb_switch_to_host()(kvm); } |