powerpc/64s: fix scv entry fallback flush vs interrupt

The L1D flush fallback functions are not recoverable vs interrupts,
yet the scv entry flush runs with MSR[EE]=1. This can result in a
timer (soft-NMI) or MCE or SRESET interrupt hitting here and overwriting
the EXRFI save area, which ends up corrupting userspace registers for
scv return.

Fix this by disabling RI and EE for the scv entry fallback flush.

Fixes: f79643787e0a0 ("powerpc/64s: flush L1D on kernel entry")
Cc: stable@vger.kernel.org # 5.9+ which also have flush L1D patch backport
Reported-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210111062408.287092-1-npiggin@gmail.com

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 1d32b174ab6aec3fb5403c11bddd7f938a78c2e8..c1a8aac01cf91d2917e923044cef69886f6eb367 100644 (file)
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -63,6 +63,12 @@
        nop;                                                            \
        nop;
 
+#define SCV_ENTRY_FLUSH_SLOT                                           \
+       SCV_ENTRY_FLUSH_FIXUP_SECTION;                                  \
+       nop;                                                            \
+       nop;                                                            \
+       nop;
+
 /*
  * r10 must be free to use, r13 must be paca
  */
@@ -70,6 +76,13 @@
        STF_ENTRY_BARRIER_SLOT;                                         \
        ENTRY_FLUSH_SLOT
 
+/*
+ * r10, ctr must be free to use, r13 must be paca
+ */
+#define SCV_INTERRUPT_TO_KERNEL                                                \
+       STF_ENTRY_BARRIER_SLOT;                                         \
+       SCV_ENTRY_FLUSH_SLOT
+
 /*
  * Macros for annotating the expected destination of (h)rfid
  *

diff --git a/arch/powerpc/include/asm/feature-fixups.h b/arch/powerpc/include/asm/feature-fixups.h
index f6d2acb574252e4810c8cff1455b23cf8cb2cedf..ac605fc369c42326d8537d0be9239e41dc937c6f 100644 (file)
--- a/arch/powerpc/include/asm/feature-fixups.h
+++ b/arch/powerpc/include/asm/feature-fixups.h
@@ -240,6 +240,14 @@ label##3:                                          \
        FTR_ENTRY_OFFSET 957b-958b;                     \
        .popsection;
 
+#define SCV_ENTRY_FLUSH_FIXUP_SECTION                  \
+957:                                                   \
+       .pushsection __scv_entry_flush_fixup,"a";       \
+       .align 2;                                       \
+958:                                                   \
+       FTR_ENTRY_OFFSET 957b-958b;                     \
+       .popsection;
+
 #define RFI_FLUSH_FIXUP_SECTION                                \
 951:                                                   \
        .pushsection __rfi_flush_fixup,"a";             \
@@ -273,10 +281,12 @@ label##3:                                         \
 
 extern long stf_barrier_fallback;
 extern long entry_flush_fallback;
+extern long scv_entry_flush_fallback;
 extern long __start___stf_entry_barrier_fixup, __stop___stf_entry_barrier_fixup;
 extern long __start___stf_exit_barrier_fixup, __stop___stf_exit_barrier_fixup;
 extern long __start___uaccess_flush_fixup, __stop___uaccess_flush_fixup;
 extern long __start___entry_flush_fixup, __stop___entry_flush_fixup;
+extern long __start___scv_entry_flush_fixup, __stop___scv_entry_flush_fixup;
 extern long __start___rfi_flush_fixup, __stop___rfi_flush_fixup;
 extern long __start___barrier_nospec_fixup, __stop___barrier_nospec_fixup;
 extern long __start__btb_flush_fixup, __stop__btb_flush_fixup;

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index aa1af139d947297fdac16126fdb7b48d4d189a2b..33ddfeef4fe9ed4a8eb13f38964cc195e896d7c4 100644 (file)
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -75,7 +75,7 @@ BEGIN_FTR_SECTION
        bne     .Ltabort_syscall
 END_FTR_SECTION_IFSET(CPU_FTR_TM)
 #endif
-       INTERRUPT_TO_KERNEL
+       SCV_INTERRUPT_TO_KERNEL
        mr      r10,r1
        ld      r1,PACAKSAVE(r13)
        std     r10,0(r1)

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index e02ad6fefa46cc4232199fddac38353c5433246b..6e53f76387374bc7f0485246bbc018f7ed21947f 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -2993,6 +2993,25 @@ TRAMP_REAL_BEGIN(entry_flush_fallback)
        ld      r11,PACA_EXRFI+EX_R11(r13)
        blr
 
+/*
+ * The SCV entry flush happens with interrupts enabled, so it must disable
+ * to prevent EXRFI being clobbered by NMIs (e.g., soft_nmi_common). r10
+ * (containing LR) does not need to be preserved here because scv entry
+ * puts 0 in the pt_regs, CTR can be clobbered for the same reason.
+ */
+TRAMP_REAL_BEGIN(scv_entry_flush_fallback)
+       li      r10,0
+       mtmsrd  r10,1
+       lbz     r10,PACAIRQHAPPENED(r13)
+       ori     r10,r10,PACA_IRQ_HARD_DIS
+       stb     r10,PACAIRQHAPPENED(r13)
+       std     r11,PACA_EXRFI+EX_R11(r13)
+       L1D_DISPLACEMENT_FLUSH
+       ld      r11,PACA_EXRFI+EX_R11(r13)
+       li      r10,MSR_RI
+       mtmsrd  r10,1
+       blr
+
 TRAMP_REAL_BEGIN(rfi_flush_fallback)
        SET_SCRATCH0(r13);
        GET_PACA(r13);

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 4ab426b8b0e02276423241b25d2386eedc24b90e..72fa3c00229a56ebfab492c563a2678c8fbc8bc2 100644 (file)
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -145,6 +145,13 @@ SECTIONS
                __stop___entry_flush_fixup = .;
        }
 
+       . = ALIGN(8);
+       __scv_entry_flush_fixup : AT(ADDR(__scv_entry_flush_fixup) - LOAD_OFFSET) {
+               __start___scv_entry_flush_fixup = .;
+               *(__scv_entry_flush_fixup)
+               __stop___scv_entry_flush_fixup = .;
+       }
+
        . = ALIGN(8);
        __stf_exit_barrier_fixup : AT(ADDR(__stf_exit_barrier_fixup) - LOAD_OFFSET) {
                __start___stf_exit_barrier_fixup = .;

diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c
index 47821055b94c933851a3a213f25238707bbc3d9a..1fd31b4b0e139e36715f49fbd2928f5384d6ed3b 100644 (file)
--- a/arch/powerpc/lib/feature-fixups.c
+++ b/arch/powerpc/lib/feature-fixups.c
@@ -290,9 +290,6 @@ void do_entry_flush_fixups(enum l1d_flush_type types)
        long *start, *end;
        int i;
 
-       start = PTRRELOC(&__start___entry_flush_fixup);
-       end = PTRRELOC(&__stop___entry_flush_fixup);
-
        instrs[0] = 0x60000000; /* nop */
        instrs[1] = 0x60000000; /* nop */
        instrs[2] = 0x60000000; /* nop */
@@ -312,6 +309,8 @@ void do_entry_flush_fixups(enum l1d_flush_type types)
        if (types & L1D_FLUSH_MTTRIG)
                instrs[i++] = 0x7c12dba6; /* mtspr TRIG2,r0 (SPR #882) */
 
+       start = PTRRELOC(&__start___entry_flush_fixup);
+       end = PTRRELOC(&__stop___entry_flush_fixup);
        for (i = 0; start < end; start++, i++) {
                dest = (void *)start + *start;
 
@@ -328,6 +327,25 @@ void do_entry_flush_fixups(enum l1d_flush_type types)
                patch_instruction((struct ppc_inst *)(dest + 2), ppc_inst(instrs[2]));
        }
 
+       start = PTRRELOC(&__start___scv_entry_flush_fixup);
+       end = PTRRELOC(&__stop___scv_entry_flush_fixup);
+       for (; start < end; start++, i++) {
+               dest = (void *)start + *start;
+
+               pr_devel("patching dest %lx\n", (unsigned long)dest);
+
+               patch_instruction((struct ppc_inst *)dest, ppc_inst(instrs[0]));
+
+               if (types == L1D_FLUSH_FALLBACK)
+                       patch_branch((struct ppc_inst *)(dest + 1), (unsigned long)&scv_entry_flush_fallback,
+                                    BRANCH_SET_LINK);
+               else
+                       patch_instruction((struct ppc_inst *)(dest + 1), ppc_inst(instrs[1]));
+
+               patch_instruction((struct ppc_inst *)(dest + 2), ppc_inst(instrs[2]));
+       }
+
+
        printk(KERN_DEBUG "entry-flush: patched %d locations (%s flush)\n", i,
                (types == L1D_FLUSH_NONE)       ? "no" :
                (types == L1D_FLUSH_FALLBACK)   ? "fallback displacement" :