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Re: [Qemu-devel] [RFC PATCH 01/13] intel_iommu: allocate new key when cr


From: Liu, Yi L
Subject: Re: [Qemu-devel] [RFC PATCH 01/13] intel_iommu: allocate new key when creating new address space
Date: Mon, 12 Dec 2016 16:16:50 +0800
User-agent: Mutt/1.5.21 (2010-09-15)

On Tue, Dec 06, 2016 at 06:36:16PM +0800, Peter Xu wrote:
> From: Jason Wang <address@hidden>
> 
> We use the pointer to stack for key for new address space, this will
> break hash table searching, fixing by g_malloc() a new key instead.
> 
> Cc: Michael S. Tsirkin <address@hidden>
> Cc: Paolo Bonzini <address@hidden>
> Cc: Richard Henderson <address@hidden>
> Cc: Eduardo Habkost <address@hidden>
> Acked-by: Peter Xu <address@hidden>
> Signed-off-by: Jason Wang <address@hidden>
> Signed-off-by: Peter Xu <address@hidden>
> ---
>  hw/i386/intel_iommu.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 708770e..92e4064 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -2426,12 +2426,13 @@ VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, 
> PCIBus *bus, int devfn)
>      VTDAddressSpace *vtd_dev_as;
>  
>      if (!vtd_bus) {
> +        uintptr_t *new_key = g_malloc(sizeof(*new_key));
> +        *new_key = (uintptr_t)bus;
>          /* No corresponding free() */
>          vtd_bus = g_malloc0(sizeof(VTDBus) + sizeof(VTDAddressSpace *) * \
>                              X86_IOMMU_PCI_DEVFN_MAX);
>          vtd_bus->bus = bus;
> -        key = (uintptr_t)bus;
> -        g_hash_table_insert(s->vtd_as_by_busptr, &key, vtd_bus);
> +        g_hash_table_insert(s->vtd_as_by_busptr, new_key, vtd_bus);
Hi Peter,
Your fix seems to answer an issue I encountered back in Oct. The symptom is: 
use the same bus value to
searcha previous inserted entry in s->vtd_as_by_busptr, the result is not found.

really grt fix. could explain it a bit on why this change would fix the issue?

Regards,
Yi L
>      }
>  
>      vtd_dev_as = vtd_bus->dev_as[devfn];
> -- 
> 2.7.4
> 
> 



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