ARM: KVM: force cache clean on page fault when caches are off

commit 159793001d7d85af17855630c94f0a176848e16b upstream.

In order for a guest with caches disabled to observe data written
contained in a given page, we need to make sure that page is
committed to memory, and not just hanging in the cache (as guest
accesses are completely bypassing the cache until it decides to
enable it).

For this purpose, hook into the coherent_cache_guest_page
function and flush the region if the guest SCTLR
register doesn't show the MMU and caches as being enabled.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 0de650faf1af700c2958befdf1f3b6023747fb25..1de3a9b7bab6328e176a7b78f79a760b7c8281b8 100644 (file)
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -118,9 +118,18 @@ static inline void kvm_set_s2pte_writable(pte_t *pte)
 
 struct kvm;
 
+#define kvm_flush_dcache_to_poc(a,l)   __cpuc_flush_dcache_area((a), (l))
+
+static inline bool vcpu_has_cache_enabled(struct kvm_vcpu *vcpu)
+{
+       return (vcpu->arch.cp15[c1_SCTLR] & 0b101) == 0b101;
+}
+
 static inline void coherent_cache_guest_page(struct kvm_vcpu *vcpu, hva_t hva,
                                            unsigned long size)
 {
+       if (!vcpu_has_cache_enabled(vcpu))
+               kvm_flush_dcache_to_poc((void *)hva, size);
        /*
         * If we are going to insert an instruction page and the icache is
         * either VIPT or PIPT, there is a potential problem where the host
@@ -141,8 +150,6 @@ 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))
-
 void stage2_flush_vm(struct kvm *kvm);
 
 #endif /* !__ASSEMBLY__ */