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authorMarc Zyngier <marc.zyngier@arm.com>2018-04-06 14:27:28 +0300
committerMarc Zyngier <marc.zyngier@arm.com>2018-07-09 13:37:41 +0300
commite48d53a91f6e90873e21a5ca5e8c0d7a9f8936a4 (patch)
tree8226aa3bd5ae8eefb39ad90d66fff26917bd747b /virt/kvm
parent1e4b044d22517cae7047c99038abb444423243ca (diff)
downloadlinux-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/kvm')
-rw-r--r--virt/kvm/arm/mmu.c4
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)