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| author | Nicholas Piggin <npiggin@gmail.com> | 2020-02-26 03:35:25 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2020-04-01 13:42:12 +1100 |
| commit | 2babd6ea43edacfc1577432baa187a7d212f3f4f (patch) | |
| tree | 3c1e7f7df92915c79139b66761f6385883074d22 /arch/powerpc/kernel/exceptions-64s.S | |
| parent | 9d598f934470dc455dac01f0dcbebecf1604606f (diff) | |
| download | lwn-2babd6ea43edacfc1577432baa187a7d212f3f4f.tar.gz lwn-2babd6ea43edacfc1577432baa187a7d212f3f4f.zip | |
powerpc/64s/exception: Avoid touching the stack in hdecrementer
The hdec interrupt handler is reported to sometimes fire in Linux if
KVM leaves it pending after a guest exists. This is harmless, so there
is a no-op handler for it.
The interrupt handler currently uses the regular kernel stack. Change
this to avoid touching the stack entirely.
This should be the last place where the regular Linux stack can be
accessed with asynchronous interrupts (including PMI) soft-masked.
It might be possible to take advantage of this invariant, e.g., to
context switch the kernel stack SLB entry without clearing MSR[EE].
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200225173541.1549955-17-npiggin@gmail.com
Diffstat (limited to 'arch/powerpc/kernel/exceptions-64s.S')
| -rw-r--r-- | arch/powerpc/kernel/exceptions-64s.S | 25 |
1 files changed, 20 insertions, 5 deletions
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index da15ec4fc8cb..146afa0922fb 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -1507,6 +1507,8 @@ EXC_COMMON_BEGIN(decrementer_common) INT_DEFINE_BEGIN(hdecrementer) IVEC=0x980 IHSRR=EXC_HV + ISTACK=0 + IRECONCILE=0 IKVM_REAL=1 IKVM_VIRT=1 INT_DEFINE_END(hdecrementer) @@ -1518,11 +1520,24 @@ EXC_VIRT_BEGIN(hdecrementer, 0x4980, 0x80) GEN_INT_ENTRY hdecrementer, virt=1 EXC_VIRT_END(hdecrementer, 0x4980, 0x80) EXC_COMMON_BEGIN(hdecrementer_common) - GEN_COMMON hdecrementer - bl save_nvgprs - addi r3,r1,STACK_FRAME_OVERHEAD - bl hdec_interrupt - b ret_from_except + __GEN_COMMON_ENTRY hdecrementer + /* + * Hypervisor decrementer interrupts not caught by the KVM test + * shouldn't occur but are sometimes left pending on exit from a KVM + * guest. We don't need to do anything to clear them, as they are + * edge-triggered. + * + * Be careful to avoid touching the kernel stack. + */ + ld r10,PACA_EXGEN+EX_CTR(r13) + mtctr r10 + mtcrf 0x80,r9 + ld r9,PACA_EXGEN+EX_R9(r13) + ld r10,PACA_EXGEN+EX_R10(r13) + ld r11,PACA_EXGEN+EX_R11(r13) + ld r12,PACA_EXGEN+EX_R12(r13) + ld r13,PACA_EXGEN+EX_R13(r13) + HRFI_TO_KERNEL GEN_KVM hdecrementer |