[PATCH 4.19 54/85] arm64: KVM: regmap: Fix unexpected switch fall-through

Greg Kroah-Hartman
2019-08-22T17:27:25Z

From: Anders Roxell <anders.roxell@linaro.org>

commit 3d584a3c85d6fe2cf878f220d4ad7145e7f89218 upstream.

When fall-through warnings was enabled by default, commit d93512ef0f0e
("Makefile: Globally enable fall-through warning"), the following
warnings was starting to show up:

In file included from ../arch/arm64/include/asm/kvm_emulate.h:19,
from ../arch/arm64/kvm/regmap.c:13:
../arch/arm64/kvm/regmap.c: In function ‘vcpu_write_spsr32’:
../arch/arm64/include/asm/kvm_hyp.h:31:3: warning: this statement may fall
through [-Wimplicit-fallthrough=]
asm volatile(ALTERNATIVE(__msr_s(r##nvh, "%x0"), \
^~~
../arch/arm64/include/asm/kvm_hyp.h:46:31: note: in expansion of macro ‘write_sysreg_elx’
#define write_sysreg_el1(v,r) write_sysreg_elx(v, r, _EL1, _EL12)
^~~~~~~~~~~~~~~~
../arch/arm64/kvm/regmap.c:180:3: note: in expansion of macro ‘write_sysreg_el1’
write_sysreg_el1(v, SYS_SPSR);
^~~~~~~~~~~~~~~~
../arch/arm64/kvm/regmap.c:181:2: note: here
case KVM_SPSR_ABT:
^~~~
In file included from ../arch/arm64/include/asm/cputype.h:132,
from ../arch/arm64/include/asm/cache.h:8,
from ../include/linux/cache.h:6,
from ../include/linux/printk.h:9,
from ../include/linux/kernel.h:15,
from ../include/asm-generic/bug.h:18,
from ../arch/arm64/include/asm/bug.h:26,
from ../include/linux/bug.h:5,
from ../include/linux/mmdebug.h:5,
from ../include/linux/mm.h:9,
from ../arch/arm64/kvm/regmap.c:11:
../arch/arm64/include/asm/sysreg.h:837:2: warning: this statement may fall
through [-Wimplicit-fallthrough=]
asm volatile("msr " __stringify(r) ", %x0" \
^~~
../arch/arm64/kvm/regmap.c:182:3: note: in expansion of macro ‘write_sysreg’
write_sysreg(v, spsr_abt);
^~~~~~~~~~~~
../arch/arm64/kvm/regmap.c:183:2: note: here
case KVM_SPSR_UND:
^~~~

Rework to add a 'break;' in the swich-case since it didn't have that,
leading to an interresting set of bugs.

Cc: stable@vger.kernel.org # v4.17+
Fixes: a892819560c4 ("KVM: arm64: Prepare to handle deferred save/restore of 32-bit registers")
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
[maz: reworked commit message, fixed stable range]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm64/kvm/regmap.c | 5 +++++
1 file changed, 5 insertions(+)

--- a/arch/arm64/kvm/regmap.c
+++ b/arch/arm64/kvm/regmap.c
@@ -189,13 +189,18 @@ void vcpu_write_spsr32(struct kvm_vcpu *
switch (spsr_idx) {
case KVM_SPSR_SVC:
write_sysreg_el1(v, spsr);
+ break;
case KVM_SPSR_ABT:
write_sysreg(v, spsr_abt);
+ break;
case KVM_SPSR_UND:
write_sysreg(v, spsr_und);
+ break;
case KVM_SPSR_IRQ:
write_sysreg(v, spsr_irq);
+ break;
case KVM_SPSR_FIQ:
write_sysreg(v, spsr_fiq);
+ break;
}
}