linux-stable.git/arch/powerpc/kernel/interrupt.c, branch linux-5.14.y

powerpc/64s/interrupt: Fix check_return_regs_valid() false positive

2021-11-17T10:04:50+00:00

commit 4a5cb51f3db4be547225a4bce7a43d41b231382b upstream.

The check_return_regs_valid() can cause a false positive if the return
regs are marked as norestart and they are an HSRR type interrupt,
because the low bit in the bottom of regs->trap causes interrupt type
matching to fail.

This can occcur for example on bare metal with a HV privileged doorbell
interrupt that causes a signal, but do_signal returns early because
get_signal() fails, and takes the "No signal to deliver" path. In this
case no signal was delivered so the return location is not changed so
return SRRs are not invalidated, yet set_trap_norestart is called, which
messes up the match. Building go-1.16.6 is known to reproduce this.

Fix it by using the TRAP() accessor which masks out the low bit.

Fixes: 6eaaf9de3599 ("powerpc/64s/interrupt: Check and fix srr_valid without crashing")
Cc: stable@vger.kernel.org # v5.14+
Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20211026122531.3599918-1-npiggin@gmail.com
Signed-off-by: Greg Kroah-Hartman

powerpc/64s: system call rfscv workaround for TM bugs

2021-09-22T10:39:22+00:00

commit ae7aaecc3f2f78b76ab3a8d6178610f55aadfa56 upstream.

The rfscv instruction does not work correctly with the fake-suspend mode
in POWER9, which can end up with the hypervisor restoring an incorrect
checkpoint.

Work around this by setting the _TIF_RESTOREALL flag if a system call
returns to a transaction active state, causing rfid to be used instead
of rfscv to return, which will do the right thing. The contents of the
registers are irrelevant because they will be overwritten in this case
anyway.

Fixes: 7fa95f9adaee7 ("powerpc/64s: system call support for scv/rfscv instructions")
Reported-by: Eirik Fuller 
Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210908101718.118522-1-npiggin@gmail.com
Signed-off-by: Greg Kroah-Hartman

powerpc/64s: system call scv tabort fix for corrupt irq soft-mask state

2021-09-22T10:39:20+00:00

commit b871895b148256f1721bc565d803860242755a0b upstream.

If a system call is made with a transaction active, the kernel
immediately aborts it and returns. scv system calls disable irqs even
earlier in their interrupt handler, and tabort_syscall does not fix this
up.

This can result in irq soft-mask state being messed up on the next
kernel entry, and crashing at BUG_ON(arch_irq_disabled_regs(regs)) in
the kernel exit handlers, or possibly worse.

This can't easily be fixed in asm because at this point an async irq may
have hit, which is soft-masked and marked pending. The pending interrupt
has to be replayed before returning to userspace. The fix is to move the
tabort_syscall code to C in the main syscall handler, and just skip the
system call but otherwise return as usual, which will take care of the
pending irqs. This also does a bunch of other things including possible
signal delivery to the process, but the doomed transaction should still
be aborted when it is eventually returned to.

The sc system call path is changed to use the new C function as well to
reduce code and path differences. This slows down how quickly system
calls are aborted when called while a transaction is active, which could
potentially impact TM performance. But making any system call is already
bad for performance, and TM is on the way out, so go with simpler over
faster.

Fixes: 7fa95f9adaee7 ("powerpc/64s: system call support for scv/rfscv instructions")
Reported-by: Eirik Fuller 
Signed-off-by: Nicholas Piggin 
[mpe: Use #ifdef rather than IS_ENABLED() to fix build error on 32-bit]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210903125707.1601269-1-npiggin@gmail.com
Signed-off-by: Greg Kroah-Hartman

powerpc/64e: remove implicit soft-masking and interrupt exit restart logic

2021-06-30T12:21:20+00:00

The implicit soft-masking to speed up interrupt return was going to be
used by 64e as well, but it has not been extensively tested on that
platform and is not considered ready. It was intended to be disabled
before merge. Disable it for now.

Most of the restart code is common with 64s, so with more correctness
and performance testing this could be re-enabled again by adding the
extra soft-mask checks to interrupt handlers and flipping
exit_must_hard_disable().

Fixes: 9d1988ca87dd ("powerpc/64: treat low kernel text as irqs soft-masked")
Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210630074621.2109197-4-npiggin@gmail.com

powerpc/interrupt: Use names in check_return_regs_valid()

2021-06-26T00:59:21+00:00

trap->regs == 0x3000 is trap_is_scv()

trap 0x500 is INTERRUPT_EXTERNAL

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/d48bf0184a1de185eb0ed3282247f8a294710674.1624632537.git.christophe.leroy@csgroup.eu

powerpc/interrupt: Also use exit_must_hard_disable() on PPC32

2021-06-25T23:43:34+00:00

Reduce #ifdefs a bit by making exit_must_hard_disable() return
true on PPC32.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/52531029563c1fc823b790058e799d0ca71b028c.1624631463.git.christophe.leroy@csgroup.eu

powerpc/64s/interrupt: Check and fix srr_valid without crashing

2021-06-24T14:06:57+00:00

The PPC_RFI_SRR_DEBUG check added by patch "powerpc/64s: avoid reloading
(H)SRR registers if they are still valid" has a few deficiencies. It
does not fix the actual problem, it's not enabled by default, and it
causes a program check interrupt which can cause more difficulties.

However there are a lot of paths which may clobber SRRs or change return
regs, and difficult to have a high confidence that all paths are covered
without wider testing.

Add a relatively low overhead always-enabled check that catches most
such cases, reports once, and fixes it so the kernel can continue.

Signed-off-by: Nicholas Piggin 
[mpe: Rebase, use switch & INT names, squash in race fix from Nick]
Signed-off-by: Michael Ellerman

powerpc/interrupt: Remove prep_irq_for_user_exit()

2021-06-24T14:06:57+00:00

prep_irq_for_user_exit() has only one caller, squash it
inside that caller.

Signed-off-by: Christophe Leroy 
Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210617155116.2167984-18-npiggin@gmail.com

powerpc/interrupt: Refactor prep_irq_for_{user/kernel_enabled}_exit()

2021-06-24T14:06:57+00:00

prep_irq_for_user_exit() is a superset of
prep_irq_for_kernel_enabled_exit().

Rename prep_irq_for_kernel_enabled_exit() as prep_irq_for_enabled_exit()
and have prep_irq_for_user_exit() use it.

Signed-off-by: Christophe Leroy 
Signed-off-by: Nicholas Piggin 
Reviewed-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210617155116.2167984-17-npiggin@gmail.com

powerpc/interrupt: Interchange prep_irq_for_{kernel_enabled/user}_exit()

2021-06-24T14:06:57+00:00

prep_irq_for_user_exit() is a superset of
prep_irq_for_kernel_enabled_exit(). In order to allow refactoring in
following patch, interchange the two. This will allow
prep_irq_for_user_exit() to call a renamed version of
prep_irq_for_kernel_enabled_exit().

Signed-off-by: Christophe Leroy 
Signed-off-by: Nicholas Piggin 
Reviewed-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210617155116.2167984-16-npiggin@gmail.com