KVM: arm64: Provide __flush_dcache_area at EL2

We will need to do cache maintenance at EL2 soon, so compile a copy of
__flush_dcache_area at EL2, and provide a copy of arm64_ftr_reg_ctrel0
as it is needed by the read_ctr macro.
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210319100146.1149909-15-qperret@google.com

arch/arm64/include/asm/kvm_cpufeature.h

@@ -19,4 +19,6 @@
 #define DEFINE_KVM_HYP_CPU_FTR_REG(name) BUILD_BUG()
 #endif
 
+DECLARE_KVM_HYP_CPU_FTR_REG(arm64_ftr_reg_ctrel0);
+
 #endif

arch/arm64/kvm/hyp/nvhe/Makefile

@@ -13,7 +13,8 @@ lib-objs := clear_page.o copy_page.o memcpy.o memset.o
 lib-objs := $(addprefix ../../../lib/, $(lib-objs))
 
 obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
-	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o stub.o page_alloc.o
+	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o stub.o page_alloc.o \
+	 cache.o
 obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
 	 ../fpsimd.o ../hyp-entry.o ../exception.o
 obj-y += $(lib-objs)

arch/arm64/kvm/hyp/nvhe/cache.S

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Code copied from arch/arm64/mm/cache.S.
+ */
+
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+#include <asm/alternative.h>
+
+SYM_FUNC_START_PI(__flush_dcache_area)
+	dcache_by_line_op civac, sy, x0, x1, x2, x3
+	ret
+SYM_FUNC_END_PI(__flush_dcache_area)

arch/arm64/kvm/hyp/nvhe/hyp-smp.c

@@ -5,9 +5,15 @@
  */
 
 #include <asm/kvm_asm.h>
+#include <asm/kvm_cpufeature.h>
 #include <asm/kvm_hyp.h>
 #include <asm/kvm_mmu.h>
 
+/*
+ * Copies of the host's CPU features registers holding sanitized values.
+ */
+DEFINE_KVM_HYP_CPU_FTR_REG(arm64_ftr_reg_ctrel0);
+
 /*
  * nVHE copy of data structures tracking available CPU cores.
  * Only entries for CPUs that were online at KVM init are populated.

arch/arm64/kvm/sys_regs.c

@@ -2783,6 +2783,7 @@ struct __ftr_reg_copy_entry {
 	u32			sys_id;
 	struct arm64_ftr_reg	*dst;
 } hyp_ftr_regs[] __initdata = {
+	CPU_FTR_REG_HYP_COPY(SYS_CTR_EL0, arm64_ftr_reg_ctrel0),
 };
 
 void __init setup_kvm_el2_caps(void)