Re: [PATCH 07/11] powerpc/64s: Add support for RFI flush of L1-D cache
From: Joel Stanley <joel@jms.id.au>
Date: 2018-01-09 07:03:07
Also in:
lkml
On Mon, Jan 8, 2018 at 8:54 AM, Michael Ellerman [off-list ref] wrote:
On some CPUs we can prevent the Meltdown vulnerability by flushing the L1-D cache on exit from kernel to user mode, and from hypervisor to guest.
Super minor nitpicks below. Don't let this hold up your work.
quoted hunk ↗ jump to hunk
--- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S@@ -1449,6 +1449,88 @@ masked_##_H##interrupt: \ b .; \ MASKED_DEC_HANDLER(_H) +TRAMP_REAL_BEGIN(rfi_flush_fallback) + SET_SCRATCH0(r13); + GET_PACA(r13); + std r9,PACA_EXRFI+EX_R9(r13) + std r10,PACA_EXRFI+EX_R10(r13) + std r11,PACA_EXRFI+EX_R11(r13) + std r12,PACA_EXRFI+EX_R12(r13) + std r8,PACA_EXRFI+EX_R13(r13) + mfctr r9 + ld r10,PACA_RFI_FLUSH_FALLBACK_AREA(r13) + ld r11,PACA_L1D_FLUSH_SETS(r13) + ld r12,PACA_L1D_FLUSH_CONGRUENCE(r13) + /* + * The load adresses are at staggered offsets within cachelines, + * which suits some pipelines better (on others it should not + * hurt.
Nit: missing ) on the last line.
+ */ + addi r12,r12,8 + mtctr r11 + DCBT_STOP_ALL_STREAM_IDS(r11) /* Stop prefetch streams */ +
quoted hunk ↗ jump to hunk
--- a/arch/powerpc/lib/feature-fixups.c +++ b/arch/powerpc/lib/feature-fixups.c@@ -116,6 +116,47 @@ void do_feature_fixups(unsigned long value, void *fixup_start, void *fixup_end) } } +#ifdef CONFIG_PPC_BOOK3S_64 +void do_rfi_flush_fixups(enum l1d_flush_type types) +{ + unsigned int instrs[3], *dest; + long *start, *end; + int i; + + start = PTRRELOC(&__start___rfi_flush_fixup), + end = PTRRELOC(&__stop___rfi_flush_fixup); + + instrs[0] = 0x60000000; /* nop */ + instrs[1] = 0x60000000; /* nop */ + instrs[2] = 0x60000000; /* nop */ + + if (types & L1D_FLUSH_FALLBACK)
This looked a bit confusing on first read. Do we ever get
L1D_FLUSH_FALLBACK and the other types? If not, could it be made
clearer?
if ( types & L1D_FLUSH_FALLBACK)
/* stuff */
else
/* other types */
+ /* b .+16 to fallback flush */
+ instrs[0] = 0x48000010;
+
+ i = 0;
+ if (types & L1D_FLUSH_ORI) {
+ instrs[i++] = 0x63ff0000; /* ori 31,31,0 speculation barrier */
+ instrs[i++] = 0x63de0000; /* ori 30,30,0 L1d flush*/
+ }
+
+ if (types & L1D_FLUSH_MTTRIG)
+ instrs[i++] = 0x7c12dba6; /* mtspr TRIG2,r0 (SPR #882) */
+
+ for (i = 0; start < end; start++, i++) {
+ dest = (void *)start + *start;
+
+ pr_devel("patching dest %lx\n", (unsigned long)dest);
+
+ patch_instruction(dest, instrs[0]);
+ patch_instruction(dest + 1, instrs[1]);
+ patch_instruction(dest + 2, instrs[2]);
+ }
+
+ printk(KERN_DEBUG "rfi-flush: patched %d locations\n", i);
+}
+#endif /* CONFIG_PPC_BOOK3S_64 */
+
void do_lwsync_fixups(unsigned long value, void *fixup_start, void *fixup_end)
{
long *start, *end;
--
2.14.3