Re: [Qemu-devel] [PATCH v2 3/3] edu: uses uint64_t in dma operation

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 4/22/19 3:21 AM, Li Qiang wrote:
> 
> 
> Philippe Mathieu-Daudé <philmd@redhat.com <mailto:philmd@redhat.com>> 于
> 2019年4月21日周日 下午6:32写道：
> 
>     On 4/20/19 6:14 PM, Li Qiang wrote:
>     > The dma related variable is dma_addr_t, it is uint64_t in
>     > x64 platform. Change these usage from uint32_to uint64_t to
>     > avoid trancation.
> 
>     "to avoid address truncation"?
> 
> 
> 
> The dma.dst/src/cnt..is from guest and is 64-bits. But in 'edu_dma_timer',
> it is assigned to uint32_t, If it is 0xffffffff 00000000, it will be ok
> by the check
> but it is of course not allowed. 
> 
> Though this is just an edu device, I think we should avoid this. 

I agree with you, I was just trying to correct your English ;)

> Thanks,
> Li Qiang
> 
>  
> 
>     >
>     > Signed-off-by: Li Qiang <liq3ea@163.com <mailto:liq3ea@163.com>>
>     > ---
>     > Change since v1:
>     > Fix format compile error on Windows
>     >
>     >  hw/misc/edu.c | 15 ++++++++-------
>     >  1 file changed, 8 insertions(+), 7 deletions(-)
>     >
>     > diff --git a/hw/misc/edu.c b/hw/misc/edu.c
>     > index 4018dddcb8..f4a6d5f1c5 100644
>     > --- a/hw/misc/edu.c
>     > +++ b/hw/misc/edu.c
>     > @@ -98,23 +98,24 @@ static void edu_lower_irq(EduState *edu,
>     uint32_t val)
>     >      }
>     >  }
>     > 
>     > -static bool within(uint32_t addr, uint32_t start, uint32_t end)
>     > +static bool within(uint64_t addr, uint64_t start, uint64_t end)
> 
>     OK.
> 
>     >  {
>     >      return start <= addr && addr < end;
>     >  }
>     > 
>     > -static void edu_check_range(uint32_t addr, uint32_t size1,
>     uint32_t start,
>     > +static void edu_check_range(uint64_t addr, uint64_t size1,
>     uint64_t start,
>     >                  uint32_t size2)
> 
>     OK for addr. MMIO range is 1MiB so you can keep uint32_t for
>     size1/size2. Up to the maintainer (personally I'd prefer keep u32).
> 
>     Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com
>     <mailto:philmd@redhat.com>>
> 
>     >  {
>     > -    uint32_t end1 = addr + size1;
>     > -    uint32_t end2 = start + size2;
>     > +    uint64_t end1 = addr + size1;
>     > +    uint64_t end2 = start + size2;
>     > 
>     >      if (within(addr, start, end2) &&
>     >              end1 > addr && within(end1, start, end2)) {
>     >          return;
>     >      }
>     > 
>     > -    hw_error("EDU: DMA range 0x%.8x-0x%.8x out of bounds
>     (0x%.8x-0x%.8x)!",
>     > +    hw_error("EDU: DMA range 0x%016"PRIx64"-0x%016"PRIx64
>     > +             " out of bounds (0x%016"PRIx64"-0x%016"PRIx64")!",
>     >              addr, end1 - 1, start, end2 - 1);
>     >  }
>     > 
>     > @@ -139,13 +140,13 @@ static void edu_dma_timer(void *opaque)
>     >      }
>     > 
>     >      if (EDU_DMA_DIR(edu->dma.cmd) == EDU_DMA_FROM_PCI) {
>     > -        uint32_t dst = edu->dma.dst;
>     > +        uint64_t dst = edu->dma.dst;
>     >          edu_check_range(dst, edu->dma.cnt, DMA_START, DMA_SIZE);
>     >          dst -= DMA_START;
>     >          pci_dma_read(&edu->pdev, edu_clamp_addr(edu, edu->dma.src),
>     >                  edu->dma_buf + dst, edu->dma.cnt);
>     >      } else {
>     > -        uint32_t src = edu->dma.src;
>     > +        uint64_t src = edu->dma.src;
>     >          edu_check_range(src, edu->dma.cnt, DMA_START, DMA_SIZE);
>     >          src -= DMA_START;
>     >          pci_dma_write(&edu->pdev, edu_clamp_addr(edu, edu->dma.dst),
>     >
>