linux-kernel - [PATCH] arm64/kvm: fix -Wimplicit-fallthrough warnings

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Message-Id: <1564755788-28485-1-git-send-email-cai@lca.pw>
Date:   Fri,  2 Aug 2019 10:23:08 -0400
From:   Qian Cai <cai@....pw>
To:     maz@...nel.org
Cc:     james.morse@....com, julien.thierry.kdev@...il.com,
        suzuki.poulose@....com, christoffer.dall@...aro.org,
        drjones@...hat.com, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>
Subject: [PATCH] arm64/kvm: fix -Wimplicit-fallthrough warnings

The commit a892819560c4 ("KVM: arm64: Prepare to handle deferred
save/restore of 32-bit registers") introduced vcpu_write_spsr32() but
seems forgot to add "break" between the switch statements and generates
compilation warnings below. Also, adding a default statement as in
vcpu_read_spsr32().

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:
  ^~~~
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:184:3: note: in expansion of macro
'write_sysreg'
   write_sysreg(v, spsr_und);
   ^~~~~~~~~~~~
arch/arm64/kvm/regmap.c:185:2: note: here
  case KVM_SPSR_IRQ:
  ^~~~
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:186:3: note: in expansion of macro
'write_sysreg'
   write_sysreg(v, spsr_irq);
   ^~~~~~~~~~~~
arch/arm64/kvm/regmap.c:187:2: note: here
  case KVM_SPSR_FIQ:
  ^~~~

Fixes: a892819560c4 ("KVM: arm64: Prepare to handle deferred save/restore of 32-bit registers")
Signed-off-by: Qian Cai <cai@....pw>
---
 arch/arm64/kvm/regmap.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm64/kvm/regmap.c b/arch/arm64/kvm/regmap.c
index 0d60e4f0af66..c94e9bc3e8eb 100644
--- a/arch/arm64/kvm/regmap.c
+++ b/arch/arm64/kvm/regmap.c
@@ -178,13 +178,20 @@ void vcpu_write_spsr32(struct kvm_vcpu *vcpu, unsigned long v)
 	switch (spsr_idx) {
 	case KVM_SPSR_SVC:
 		write_sysreg_el1(v, SYS_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;
+	default:
+		BUG();
 	}
 }
-- 
1.8.3.1