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| author | Marc Zyngier <marc.zyngier@arm.com> | 2018-04-06 14:27:28 +0300 |
|---|---|---|
| committer | Marc Zyngier <marc.zyngier@arm.com> | 2018-07-09 13:37:41 +0300 |
| commit | e48d53a91f6e90873e21a5ca5e8c0d7a9f8936a4 (patch) | |
| tree | 8226aa3bd5ae8eefb39ad90d66fff26917bd747b /virt | |
| parent | 1e4b044d22517cae7047c99038abb444423243ca (diff) | |
| download | linux-e48d53a91f6e90873e21a5ca5e8c0d7a9f8936a4.tar.xz | |
arm64: KVM: Add support for Stage-2 control of memory types and cacheability
Up to ARMv8.3, the combinaison of Stage-1 and Stage-2 attributes
results in the strongest attribute of the two stages. This means
that the hypervisor has to perform quite a lot of cache maintenance
just in case the guest has some non-cacheable mappings around.
ARMv8.4 solves this problem by offering a different mode (FWB) where
Stage-2 has total control over the memory attribute (this is limited
to systems where both I/O and instruction fetches are coherent with
the dcache). This is achieved by having a different set of memory
attributes in the page tables, and a new bit set in HCR_EL2.
On such a system, we can then safely sidestep any form of dcache
management.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Diffstat (limited to 'virt')
| -rw-r--r-- | virt/kvm/arm/mmu.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c index 1d90d79706bd..ea7314296ad1 100644 --- a/virt/kvm/arm/mmu.c +++ b/virt/kvm/arm/mmu.c @@ -196,6 +196,10 @@ static void clear_stage2_pmd_entry(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr * This is why right after unmapping a page/section and invalidating * the corresponding TLBs, we call kvm_flush_dcache_p*() to make sure * the IO subsystem will never hit in the cache. + * + * This is all avoided on systems that have ARM64_HAS_STAGE2_FWB, as + * we then fully enforce cacheability of RAM, no matter what the guest + * does. */ static void unmap_stage2_ptes(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr, phys_addr_t end) |