Merge tag 'riscv/for-v5.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V fixes from Paul Walmsley:

 - Ensure that exclusive-load reservations are terminated after system
   call or exception handling. This primarily affects QEMU, which does
   not expire load reservations.

 - Fix an issue primarily affecting RV32 platforms that can cause the DT
   header to be corrupted, causing boot failures.

* tag 'riscv/for-v5.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  riscv: Fix memblock reservation for device tree blob
  RISC-V: Clear load reservations while restoring hart contexts

3 files changed, 32 insertions, 2 deletions

diff --git a/arch/riscv/include/asm/asm.h b/arch/riscv/include/asm/asm.h
index 5a02b7d50940..9c992a88d858 100644
--- a/arch/riscv/include/asm/asm.h
+++ b/arch/riscv/include/asm/asm.h
@@ -22,6 +22,7 @@
 
 #define REG_L		__REG_SEL(ld, lw)
 #define REG_S		__REG_SEL(sd, sw)
+#define REG_SC		__REG_SEL(sc.d, sc.w)
 #define SZREG		__REG_SEL(8, 4)
 #define LGREG		__REG_SEL(3, 2)
 
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index da7aa88113c2..2d592da1e776 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -98,7 +98,26 @@ _save_context:
  */
 	.macro RESTORE_ALL
 	REG_L a0, PT_SSTATUS(sp)
-	REG_L a2, PT_SEPC(sp)
+	/*
+	 * The current load reservation is effectively part of the processor's
+	 * state, in the sense that load reservations cannot be shared between
+	 * different hart contexts.  We can't actually save and restore a load
+	 * reservation, so instead here we clear any existing reservation --
+	 * it's always legal for implementations to clear load reservations at
+	 * any point (as long as the forward progress guarantee is kept, but
+	 * we'll ignore that here).
+	 *
+	 * Dangling load reservations can be the result of taking a trap in the
+	 * middle of an LR/SC sequence, but can also be the result of a taken
+	 * forward branch around an SC -- which is how we implement CAS.  As a
+	 * result we need to clear reservations between the last CAS and the
+	 * jump back to the new context.  While it is unlikely the store
+	 * completes, implementations are allowed to expand reservations to be
+	 * arbitrarily large.
+	 */
+	REG_L  a2, PT_SEPC(sp)
+	REG_SC x0, a2, PT_SEPC(sp)
+
 	csrw CSR_SSTATUS, a0
 	csrw CSR_SEPC, a2
 
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index f0ba71304b6e..83f7d12042fb 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -11,6 +11,7 @@
 #include <linux/swap.h>
 #include <linux/sizes.h>
 #include <linux/of_fdt.h>
+#include <linux/libfdt.h>
 
 #include <asm/fixmap.h>
 #include <asm/tlbflush.h>
@@ -82,6 +83,8 @@ disable:
 }
 #endif /* CONFIG_BLK_DEV_INITRD */
 
+static phys_addr_t dtb_early_pa __initdata;
+
 void __init setup_bootmem(void)
 {
 	struct memblock_region *reg;
@@ -117,7 +120,12 @@ void __init setup_bootmem(void)
 	setup_initrd();
 #endif /* CONFIG_BLK_DEV_INITRD */
 
-	early_init_fdt_reserve_self();
+	/*
+	 * Avoid using early_init_fdt_reserve_self() since __pa() does
+	 * not work for DTB pointers that are fixmap addresses
+	 */
+	memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
+
 	early_init_fdt_scan_reserved_mem();
 	memblock_allow_resize();
 	memblock_dump_all();
@@ -393,6 +401,8 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 
 	/* Save pointer to DTB for early FDT parsing */
 	dtb_early_va = (void *)fix_to_virt(FIX_FDT) + (dtb_pa & ~PAGE_MASK);
+	/* Save physical address for memblock reservation */
+	dtb_early_pa = dtb_pa;
 }
 
 static void __init setup_vm_final(void)