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Re: [Qemu-devel] [PATCH] pci: fix compilation warnings

From: Marcel Apfelbaum
Subject: Re: [Qemu-devel] [PATCH] pci: fix compilation warnings
Date: Mon, 28 Mar 2016 12:53:17 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0

On 03/28/2016 11:43 AM, Stefan Weil wrote:
Am 28.03.2016 um 09:23 schrieb Marcel Apfelbaum:
Fix 'error: shift exponent -1 is negative' warning
by adding a corresponding assert.

Reported-by: Peter Maydell <address@hidden>
Signed-off-by: Markus Armbruster <address@hidden>
Signed-off-by: Marcel Apfelbaum <address@hidden>
  hw/pci/pci.c | 4 ++++
  1 file changed, 4 insertions(+)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index e67664d..a1d41aa 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -163,11 +163,15 @@ int pci_bar(PCIDevice *d, int reg)

  static inline int pci_irq_state(PCIDevice *d, int irq_num)
+    assert(irq_num >= 0);
        return (d->irq_state >> irq_num) & 0x1;

  static inline void pci_set_irq_state(PCIDevice *d, int irq_num, int level)
+    assert(irq_num >= 0);
        d->irq_state &= ~(0x1 << irq_num);
        d->irq_state |= level << irq_num;

Do we use negative values for irq_num anywhere?

Hi Stefan,

I didn't see any irq_nu assignments to a negative value but there are
some cases where it can be negative due to arithmetical operations like:

   hw/pci-host/bonito.c:651:    int internal_irq = irq_num - BONITO_IRQ_BASE;

On other cases we look for negative value:

   hw/ppc/ppc4xx_devs.c:171:    if (irq_num < 0 || irq_num > 3)
   hw/ppc/ppc4xx_pci.c:263:    if (irq_num < 0)

If not, using an unsigned irq_num might be a better solution.

All of the above are manageable, of course, but we are close to
hard freeze (tomorrow) and the scope of this patch is much smaller (fix a 
compilation warning)

I think is definitely worth looking into it, but maybe as part of QEMU 2.7.



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