[PATCH v4 7/7] stm32mp: don't map the reserved region with no-map property

[Patrick Delaunay]

No more map the reserved region with "no-map" property by marking
the corresponding TLB entries with invalid entry (=0) to avoid
speculative access.

The device tree parsing done in lmb_init_and_reserve() takes a
long time when it is executed without data cache, so it is called in
enable_caches() before to disable it.

This patch fixes an issue where predictive read access on secure DDR
OP-TEE reserved area are caught by firewall.

  Series-cc: marex
  Series-cc: pch
  Series-cc: marek.bykowski at gmail.com
  Series-cc: Ard Biesheuvel <ardb at kernel.org>
  Series-cc: Etienne Carriere <etienne.carriere at linaro.org>

Signed-off-by: Patrick Delaunay <patrick.delaunay at foss.st.com>
---

(no changes since v3)

Changes in v3:
- call lmb_init_and_reserve when data cache is activated in enable_caches()
- drop v2 patch "arm: cache: cp15: don't map the reserved region
  with no-map property"

Changes in v2:
- NEW: update in stm32mp specific MMU setup functions

 arch/arm/mach-stm32mp/cpu.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-stm32mp/cpu.c b/arch/arm/mach-stm32mp/cpu.c
index 8115d58b19..592bfd413d 100644
--- a/arch/arm/mach-stm32mp/cpu.c
+++ b/arch/arm/mach-stm32mp/cpu.c
@@ -12,6 +12,7 @@
 #include <env.h>
 #include <init.h>
 #include <log.h>
+#include <lmb.h>
 #include <misc.h>
 #include <net.h>
 #include <asm/io.h>
@@ -90,6 +91,8 @@
  */
 u8 early_tlb[PGTABLE_SIZE] __section(".data") __aligned(0x4000);
 
+struct lmb lmb;
+
 #if !defined(CONFIG_SPL) || defined(CONFIG_SPL_BUILD)
 #ifndef CONFIG_TFABOOT
 static void security_init(void)
@@ -221,6 +224,8 @@ void dram_bank_mmu_setup(int bank)
 	int	i;
 	phys_addr_t start;
 	phys_size_t size;
+	bool use_lmb = false;
+	enum dcache_option option;
 
 	if (IS_ENABLED(CONFIG_SPL_BUILD)) {
 		start = ALIGN_DOWN(STM32_SYSRAM_BASE, MMU_SECTION_SIZE);
@@ -229,6 +234,7 @@ void dram_bank_mmu_setup(int bank)
 		/* bd->bi_dram is available only after relocation */
 		start = bd->bi_dram[bank].start;
 		size =  bd->bi_dram[bank].size;
+		use_lmb = true;
 	} else {
 		/* mark cacheable and executable the beggining of the DDR */
 		start = STM32_DDR_BASE;
@@ -237,8 +243,12 @@ void dram_bank_mmu_setup(int bank)
 
 	for (i = start >> MMU_SECTION_SHIFT;
 	     i < (start >> MMU_SECTION_SHIFT) + (size >> MMU_SECTION_SHIFT);
-	     i++)
-		set_section_dcache(i, DCACHE_DEFAULT_OPTION);
+	     i++) {
+		option = DCACHE_DEFAULT_OPTION;
+		if (use_lmb && lmb_is_reserved_flags(&lmb, i << MMU_SECTION_SHIFT, LMB_NOMAP))
+			option = 0; /* INVALID ENTRY in TLB */
+		set_section_dcache(i, option);
+	}
 }
 /*
  * initialize the MMU and activate cache in SPL or in U-Boot pre-reloc stage
@@ -302,6 +312,9 @@ int arch_cpu_init(void)
 
 void enable_caches(void)
 {
+	/* parse device tree when data cache is still activated */
+	lmb_init_and_reserve(&lmb, gd->bd, (void *)gd->fdt_blob);
+
 	/* I-cache is already enabled in start.S: icache_enable() not needed */
 
 	/* deactivate the data cache, early enabled in arch_cpu_init() */
-- 
2.17.1