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: sta...@vger.kernel.org # 5.9+ which also have flush L1D patch backport
Cc: Daniel Axtens <d...@axtens.net>
Reported-by: Tulio Magno Quites Machado Filho <tul...@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
This applies to stable kernels 5.9+ (with scv support), which have
backported commit f79643787e0a0 ("powerpc/64s: flush L1D on kernel entry")
which was upstreamed in 5.10 but was backported. Maybe only 5.10 if
there will be no more 5.9 kernels.
arch/powerpc/include/asm/exception-64s.h | 13 ++++++++++++
arch/powerpc/include/asm/feature-fixups.h | 10 ++++++++++
arch/powerpc/kernel/entry_64.S | 2 +-
arch/powerpc/kernel/exceptions-64s.S | 19 ++++++++++++++++++
arch/powerpc/kernel/vmlinux.lds.S | 7 +++++++
arch/powerpc/lib/feature-fixups.c | 24 ++++++++++++++++++++---
6 files changed, 71 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/include/asm/exception-64s.h
b/arch/powerpc/include/asm/exception-64s.h
index 1d32b174ab6a..c1a8aac01cf9 100644
--- 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 f6d2acb57425..ac605fc369c4 100644
--- 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 aa1af139d947..33ddfeef4fe9 100644
--- 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 e02ad6fefa46..6e53f7638737 100644
--- 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 0318ba436f34..377f5f8b1514 100644
--- 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 47821055b94c..1fd31b4b0e13 100644
--- 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" :
--
2.23.0
