[RFC PATCH v1 04/21] RISC-V: ACPI: Enhance acpi_os_ioremap with MMIO remapping

Sunil V L
2023-08-03T18:00:37Z

Enhance the acpi_os_ioremap() to support opregions in MMIO
space. Also, have strict checks using EFI memory map
to allow remapping the RAM similar to arm64.

Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
---
arch/riscv/Kconfig | 1 +
arch/riscv/kernel/acpi.c | 86 +++++++++++++++++++++++++++++++++++++++-
2 files changed, 86 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 318f62a0a187..e19f32c12a68 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -38,6 +38,7 @@ config RISCV
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAS_UBSAN_SANITIZE_ALL
select ARCH_HAS_VDSO_DATA
+ select ARCH_KEEP_MEMBLOCK
select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
select ARCH_STACKWALK
diff --git a/arch/riscv/kernel/acpi.c b/arch/riscv/kernel/acpi.c
index 56cb2c986c48..aa4433bca6d9 100644
--- a/arch/riscv/kernel/acpi.c
+++ b/arch/riscv/kernel/acpi.c
@@ -17,6 +17,7 @@
#include <linux/io.h>
#include <linux/pci.h>
#include <linux/efi.h>
+#include <linux/memblock.h>

int acpi_noirq = 1; /* skip ACPI IRQ initialization */
int acpi_disabled = 1;
@@ -217,7 +218,90 @@ void __init __acpi_unmap_table(void __iomem *map, unsigned long size)

void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size)
{
- return (void __iomem *)memremap(phys, size, MEMREMAP_WB);
+ efi_memory_desc_t *md, *region = NULL;
+ pgprot_t prot;
+
+ if (WARN_ON_ONCE(!efi_enabled(EFI_MEMMAP)))
+ return NULL;
+
+ for_each_efi_memory_desc(md) {
+ u64 end = md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT);
+
+ if (phys < md->phys_addr || phys >= end)
+ continue;
+
+ if (phys + size > end) {
+ pr_warn(FW_BUG "requested region covers multiple EFI memory regions\n");
+ return NULL;
+ }
+ region = md;
+ break;
+ }
+
+ /*
+ * It is fine for AML to remap regions that are not represented in the
+ * EFI memory map at all, as it only describes normal memory, and MMIO
+ * regions that require a virtual mapping to make them accessible to
+ * the EFI runtime services.
+ */
+ prot = PAGE_KERNEL_IO;
+ if (region) {
+ switch (region->type) {
+ case EFI_LOADER_CODE:
+ case EFI_LOADER_DATA:
+ case EFI_BOOT_SERVICES_CODE:
+ case EFI_BOOT_SERVICES_DATA:
+ case EFI_CONVENTIONAL_MEMORY:
+ case EFI_PERSISTENT_MEMORY:
+ if (memblock_is_map_memory(phys) ||
+ !memblock_is_region_memory(phys, size)) {
+ pr_warn(FW_BUG "requested region covers kernel memory @ %p\n",
+ &phys);
+ return NULL;
+ }
+
+ /*
+ * Mapping kernel memory is permitted if the region in
+ * question is covered by a single memblock with the
+ * NOMAP attribute set: this enables the use of ACPI
+ * table overrides passed via initramfs.
+ * This particular use case only requires read access.
+ */
+ fallthrough;
+
+ case EFI_RUNTIME_SERVICES_CODE:
+ /*
+ * This would be unusual, but not problematic per se,
+ * as long as we take care not to create a writable
+ * mapping for executable code.
+ */
+ prot = PAGE_KERNEL_RO;
+ break;
+
+ case EFI_ACPI_RECLAIM_MEMORY:
+ /*
+ * ACPI reclaim memory is used to pass firmware tables
+ * and other data that is intended for consumption by
+ * the OS only, which may decide it wants to reclaim
+ * that memory and use it for something else. We never
+ * do that, but we usually add it to the linear map
+ * anyway, in which case we should use the existing
+ * mapping.
+ */
+ if (memblock_is_map_memory(phys))
+ return (void __iomem *)__va(phys);
+ fallthrough;
+
+ default:
+ if (region->attribute & EFI_MEMORY_WB)
+ prot = PAGE_KERNEL;
+ else if ((region->attribute & EFI_MEMORY_WC) ||
+ (region->attribute & EFI_MEMORY_WT))
+ prot = pgprot_writecombine(PAGE_KERNEL);
+ }
+ }
+
+ return ioremap_prot(phys, size, pgprot_val(prot));
}

#ifdef CONFIG_PCI
--
2.39.2