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powerpc/watchpoint: Workaround P10 DD1 issue with VSX-32 byte instructions

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[ Upstream commit 3d2ffcdd2a982e8bbe65fa0f94fb21bf304c281e ]

POWER10 DD1 has an issue where it generates watchpoint exceptions when
it shouldn't. The conditions where this occur are:

 - octword op
 - ending address of DAWR range is less than starting address of op
 - those addresses need to be in the same or in two consecutive 512B
   blocks
 - 'op address + 64B' generates an address that has a carry into bit
   52 (crosses 2K boundary)

Handle such spurious exception by considering them as extraneous and
emulating/single-steeping instruction without generating an event.

[ravi: Fixed build warning reported by lkp@intel.com]
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201106045650.278987-1-ravi.bangoria@linux.ibm.com
Stable-dep-of: 27646b2e02b0 ("powerpc/watchpoints: Annotate atomic context in more places")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Ravi Bangoria 2020-11-06 10:26:50 +05:30 committed by Greg Kroah-Hartman
parent d021ba1142
commit 2641aa3f56
1 changed files with 65 additions and 2 deletions
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67
arch/powerpc/kernel/hw_breakpoint.c
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@ -504,6 +504,11 @@ static bool is_larx_stcx_instr(int type)
return type == LARX || type == STCX;
}
static bool is_octword_vsx_instr(int type, int size)
{
return ((type == LOAD_VSX || type == STORE_VSX) && size == 32);
}
/*
* We've failed in reliably handling the hw-breakpoint. Unregister
* it and throw a warning message to let the user know about it.
@ -554,6 +559,58 @@ static bool stepping_handler(struct pt_regs *regs, struct perf_event **bp,
return true;
}
static void handle_p10dd1_spurious_exception(struct arch_hw_breakpoint **info,
int *hit, unsigned long ea)
{
int i;
unsigned long hw_end_addr;
/*
* Handle spurious exception only when any bp_per_reg is set.
* Otherwise this might be created by xmon and not actually a
* spurious exception.
*/
for (i = 0; i < nr_wp_slots(); i++) {
if (!info[i])
continue;
hw_end_addr = ALIGN(info[i]->address + info[i]->len, HW_BREAKPOINT_SIZE);
/*
* Ending address of DAWR range is less than starting
* address of op.
*/
if ((hw_end_addr - 1) >= ea)
continue;
/*
* Those addresses need to be in the same or in two
* consecutive 512B blocks;
*/
if (((hw_end_addr - 1) >> 10) != (ea >> 10))
continue;
/*
* 'op address + 64B' generates an address that has a
* carry into bit 52 (crosses 2K boundary).
*/
if ((ea & 0x800) == ((ea + 64) & 0x800))
continue;
break;
}
if (i == nr_wp_slots())
return;
for (i = 0; i < nr_wp_slots(); i++) {
if (info[i]) {
hit[i] = 1;
info[i]->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
}
}
}
int hw_breakpoint_handler(struct die_args *args)
{
bool err = false;
@ -612,8 +669,14 @@ int hw_breakpoint_handler(struct die_args *args)
goto reset;
if (!nr_hit) {
rc = NOTIFY_DONE;
goto out;
/* Workaround for Power10 DD1 */
if (!IS_ENABLED(CONFIG_PPC_8xx) && mfspr(SPRN_PVR) == 0x800100 &&
is_octword_vsx_instr(type, size)) {
handle_p10dd1_spurious_exception(info, hit, ea);
} else {
rc = NOTIFY_DONE;
goto out;
}
}
/*