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authorMarc Zyngier <marc.zyngier@arm.com>2014-01-15 12:50:23 +0000
committerMarc Zyngier <marc.zyngier@arm.com>2014-03-03 01:15:22 +0000
commit9d218a1fcf4c6b759d442ef702842fae92e1ea61 (patch)
tree1d94bc1753a84945ef1d31c4e162c660829c2875 /arch/arm
parenta3c8bd31af260a17d626514f636849ee1cd1f63e (diff)
downloadop-kernel-dev-9d218a1fcf4c6b759d442ef702842fae92e1ea61.zip
op-kernel-dev-9d218a1fcf4c6b759d442ef702842fae92e1ea61.tar.gz
arm64: KVM: flush VM pages before letting the guest enable caches
When the guest runs with caches disabled (like in an early boot sequence, for example), all the writes are diectly going to RAM, bypassing the caches altogether. Once the MMU and caches are enabled, whatever sits in the cache becomes suddenly visible, which isn't what the guest expects. A way to avoid this potential disaster is to invalidate the cache when the MMU is being turned on. For this, we hook into the SCTLR_EL1 trapping code, and scan the stage-2 page tables, invalidating the pages/sections that have already been mapped in. Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Diffstat (limited to 'arch/arm')
-rw-r--r--arch/arm/include/asm/kvm_mmu.h2
-rw-r--r--arch/arm/kvm/mmu.c93
2 files changed, 95 insertions, 0 deletions
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 891afe7..eb85b81 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -155,6 +155,8 @@ static inline void coherent_cache_guest_page(struct kvm_vcpu *vcpu, hva_t hva,
#define kvm_flush_dcache_to_poc(a,l) __cpuc_flush_dcache_area((a), (l))
#define kvm_virt_to_phys(x) virt_to_idmap((unsigned long)(x))
+void stage2_flush_vm(struct kvm *kvm);
+
#endif /* !__ASSEMBLY__ */
#endif /* __ARM_KVM_MMU_H__ */
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index c1c08b2..d7e998c 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -187,6 +187,99 @@ static void unmap_range(struct kvm *kvm, pgd_t *pgdp,
}
}
+static void stage2_flush_ptes(struct kvm *kvm, pmd_t *pmd,
+ phys_addr_t addr, phys_addr_t end)
+{
+ pte_t *pte;
+
+ pte = pte_offset_kernel(pmd, addr);
+ do {
+ if (!pte_none(*pte)) {
+ hva_t hva = gfn_to_hva(kvm, addr >> PAGE_SHIFT);
+ kvm_flush_dcache_to_poc((void*)hva, PAGE_SIZE);
+ }
+ } while (pte++, addr += PAGE_SIZE, addr != end);
+}
+
+static void stage2_flush_pmds(struct kvm *kvm, pud_t *pud,
+ phys_addr_t addr, phys_addr_t end)
+{
+ pmd_t *pmd;
+ phys_addr_t next;
+
+ pmd = pmd_offset(pud, addr);
+ do {
+ next = kvm_pmd_addr_end(addr, end);
+ if (!pmd_none(*pmd)) {
+ if (kvm_pmd_huge(*pmd)) {
+ hva_t hva = gfn_to_hva(kvm, addr >> PAGE_SHIFT);
+ kvm_flush_dcache_to_poc((void*)hva, PMD_SIZE);
+ } else {
+ stage2_flush_ptes(kvm, pmd, addr, next);
+ }
+ }
+ } while (pmd++, addr = next, addr != end);
+}
+
+static void stage2_flush_puds(struct kvm *kvm, pgd_t *pgd,
+ phys_addr_t addr, phys_addr_t end)
+{
+ pud_t *pud;
+ phys_addr_t next;
+
+ pud = pud_offset(pgd, addr);
+ do {
+ next = kvm_pud_addr_end(addr, end);
+ if (!pud_none(*pud)) {
+ if (pud_huge(*pud)) {
+ hva_t hva = gfn_to_hva(kvm, addr >> PAGE_SHIFT);
+ kvm_flush_dcache_to_poc((void*)hva, PUD_SIZE);
+ } else {
+ stage2_flush_pmds(kvm, pud, addr, next);
+ }
+ }
+ } while (pud++, addr = next, addr != end);
+}
+
+static void stage2_flush_memslot(struct kvm *kvm,
+ struct kvm_memory_slot *memslot)
+{
+ phys_addr_t addr = memslot->base_gfn << PAGE_SHIFT;
+ phys_addr_t end = addr + PAGE_SIZE * memslot->npages;
+ phys_addr_t next;
+ pgd_t *pgd;
+
+ pgd = kvm->arch.pgd + pgd_index(addr);
+ do {
+ next = kvm_pgd_addr_end(addr, end);
+ stage2_flush_puds(kvm, pgd, addr, next);
+ } while (pgd++, addr = next, addr != end);
+}
+
+/**
+ * stage2_flush_vm - Invalidate cache for pages mapped in stage 2
+ * @kvm: The struct kvm pointer
+ *
+ * Go through the stage 2 page tables and invalidate any cache lines
+ * backing memory already mapped to the VM.
+ */
+void stage2_flush_vm(struct kvm *kvm)
+{
+ struct kvm_memslots *slots;
+ struct kvm_memory_slot *memslot;
+ int idx;
+
+ idx = srcu_read_lock(&kvm->srcu);
+ spin_lock(&kvm->mmu_lock);
+
+ slots = kvm_memslots(kvm);
+ kvm_for_each_memslot(memslot, slots)
+ stage2_flush_memslot(kvm, memslot);
+
+ spin_unlock(&kvm->mmu_lock);
+ srcu_read_unlock(&kvm->srcu, idx);
+}
+
/**
* free_boot_hyp_pgd - free HYP boot page tables
*
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