-----Original Message-----
From: acrn-dev@...
[mailto:acrn-dev@...] On Behalf Of Shiqing Gao
Sent: Tuesday, August 14, 2018 10:55 AM
To: acrn-dev@...
Subject: [acrn-dev] [PATCH] hv: treewide: fix 'Shifting value too far'

MISRA-C requires that shift operation cannot exceed the word length.

What this patch does:
- Add the pre condition for 'init_lapic' regarding to 'pcpu_id'
Currently, max 8 physical cpus are supported.
Re-design will be required if we would like to support more physical
cpus.
So, add the pre condition here to avoid the unintentional shift
operation mistakes.

- Replace the id type with uint8_t in 'vlapic_build_id'
- For VM0, it uses 'lapic_id' as its id, which is uint8_t.
- For non VM0, it uses 'vcpu_id' as its id, which is uint16_t.
Cast this id to uint8_t to make sure there is no loss of data after
left shifting 24U.

Signed-off-by: Shiqing Gao <shiqing.gao@...>
---
hypervisor/arch/x86/guest/vlapic.c | 14 ++++++++------
hypervisor/arch/x86/lapic.c | 3 +++
2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/hypervisor/arch/x86/guest/vlapic.c
b/hypervisor/arch/x86/guest/vlapic.c
index 567270f..6cc1617 100644
--- a/hypervisor/arch/x86/guest/vlapic.c
+++ b/hypervisor/arch/x86/guest/vlapic.c
@@ -169,19 +169,21 @@ static inline uint32_t vlapic_build_id(struct
acrn_vlapic *vlapic) {
struct vcpu *vcpu = vlapic->vcpu;
- uint16_t id;
+ uint8_t vlapic_id;
+ uint32_t lapic_regs_id;

if (is_vm0(vcpu->vm)) {
/* Get APIC ID sequence format from cpu_storage */
- id = per_cpu(lapic_id, vcpu->vcpu_id);
+ vlapic_id = per_cpu(lapic_id, vcpu->vcpu_id);
} else {
- id = vcpu->vcpu_id;
+ vlapic_id = (uint8_t)vcpu->vcpu_id;
}

- dev_dbg(ACRN_DBG_LAPIC, "vlapic APIC PAGE ID : 0x%08x",
- (id << APIC_ID_SHIFT));
+ lapic_regs_id = vlapic_id << APIC_ID_SHIFT;

- return (id << APIC_ID_SHIFT);
+ dev_dbg(ACRN_DBG_LAPIC, "vlapic APIC PAGE ID : 0x%08x",
+lapic_regs_id);
+
+ return lapic_regs_id;
}

static void
diff --git a/hypervisor/arch/x86/lapic.c b/hypervisor/arch/x86/lapic.c index
aa35e0a..6c7752c 100644
--- a/hypervisor/arch/x86/lapic.c
+++ b/hypervisor/arch/x86/lapic.c
@@ -209,6 +209,9 @@ void early_init_lapic(void)
}
}

+/**
+ * @pre pcpu_id < 8U
+ */
void init_lapic(uint16_t pcpu_id)
{
/* Set the Logical Destination Register */
--
1.9.1