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Re: [Xen-devel] [PATCH] Qemu MSI Cleaning Up



On Thu, 22 Sep 2011, Haitao Shan wrote:
> Hi, Ian, Keir, Jan,
> 
> This patch does cleaning up of QEMU MSI handling. The fixes are:
> 1. Changes made to MSI-X table mapping handling to eliminate the small
> windows in which guest could have access to physical MSI-X table.
> 2. MSI-X table is mapped as read-only to QEMU, as masking of MSI-X is
> already in Xen now.
> 3. For registers that coexists inside the MSI-X table (this could be
> only PBA I think), value read from physical page would be returned.
> 
> Could you please have review?
> 
> Signed-off-by:  Shan Haitao <haitao.shan@xxxxxxxxx>
> 
> 
> diff --git a/hw/pass-through.c b/hw/pass-through.c
> index 9c5620d..6ebed64 100644
> --- a/hw/pass-through.c
> +++ b/hw/pass-through.c
> @@ -92,6 +92,7 @@
> 
>  #include <unistd.h>
>  #include <sys/ioctl.h>
> +#include <assert.h>
> 
>  extern int gfx_passthru;
>  int igd_passthru = 0;
> @@ -1103,6 +1104,7 @@ static void pt_iomem_map(PCIDevice *d, int i,
> uint32_t e_phys, uint32_t e_size,
>  {
>      struct pt_dev *assigned_device  = (struct pt_dev *)d;
>      uint32_t old_ebase = assigned_device->bases[i].e_physbase;
> +    uint32_t msix_last_pfn = 0, bar_last_pfn = 0;
>      int first_map = ( assigned_device->bases[i].e_size == 0 );
>      int ret = 0;
> 
> @@ -1118,39 +1120,127 @@ static void pt_iomem_map(PCIDevice *d, int i,
> uint32_t e_phys, uint32_t e_size,
> 
>      if ( !first_map && old_ebase != -1 )
>      {
> -        add_msix_mapping(assigned_device, i);
> -        /* Remove old mapping */
> -        ret = xc_domain_memory_mapping(xc_handle, domid,
> +        if ( has_msix_mapping(assigned_device, i) )
> +        {
> +            msix_last_pfn = (assigned_device->msix->mmio_base_addr - 1 +
> +                  assigned_device->msix->total_entries * 16) >>  
> XC_PAGE_SHIFT;
> +            bar_last_pfn = (old_ebase + e_size - 1) >> XC_PAGE_SHIFT;
> +
> +            unregister_iomem(assigned_device->msix->mmio_base_addr);
> +
> +            if ( assigned_device->msix->table_off )
> +            {
> +                       ret = xc_domain_memory_mapping(xc_handle, domid,
> +                    old_ebase >> XC_PAGE_SHIFT,
> +                    assigned_device->bases[i].access.maddr >> XC_PAGE_SHIFT,
> +                    (assigned_device->msix->mmio_base_addr >> XC_PAGE_SHIFT)
> +                    - (old_ebase >> XC_PAGE_SHIFT),
> +                    DPCI_REMOVE_MAPPING);
> +                if ( ret != 0 )
> +                {
> +                    PT_LOG("Error: remove old mapping failed!\n");
> +                    return;
> +                }
> +            }
> +            if ( msix_last_pfn != bar_last_pfn )
> +            {
> +                assert(msix_last_pfn < bar_last_pfn);
> +                       ret = xc_domain_memory_mapping(xc_handle, domid,
> +                    msix_last_pfn + 1,
> +                    (assigned_device->bases[i].access.maddr +
> +                     assigned_device->msix->table_off +
> +                     assigned_device->msix->total_entries * 16 +
> +                     XC_PAGE_SIZE -1) >>  XC_PAGE_SHIFT,
> +                    bar_last_pfn - msix_last_pfn,
> +                    DPCI_REMOVE_MAPPING);
> +                if ( ret != 0 )
> +                {
> +                    PT_LOG("Error: remove old mapping failed!\n");
> +                    return;
> +                }
> +            }
> +        }
> +        else
> +        {
> +                   /* Remove old mapping */
> +                   ret = xc_domain_memory_mapping(xc_handle, domid,
>                  old_ebase >> XC_PAGE_SHIFT,
>                  assigned_device->bases[i].access.maddr >> XC_PAGE_SHIFT,
>                  (e_size+XC_PAGE_SIZE-1) >> XC_PAGE_SHIFT,
>                  DPCI_REMOVE_MAPPING);
> -        if ( ret != 0 )
> -        {
> -            PT_LOG("Error: remove old mapping failed!\n");
> -            return;
> +            if ( ret != 0 )
> +            {
> +                PT_LOG("Error: remove old mapping failed!\n");
> +                return;
> +            }
>          }
>      }
> 
>      /* map only valid guest address */
>      if (e_phys != -1)
>      {
> -        /* Create new mapping */
> -        ret = xc_domain_memory_mapping(xc_handle, domid,
> +        if ( has_msix_mapping(assigned_device, i) )
> +               {
> +            assigned_device->msix->mmio_base_addr =
> +                assigned_device->bases[i].e_physbase
> +                + assigned_device->msix->table_off;
> +
> +            msix_last_pfn = (assigned_device->msix->mmio_base_addr - 1 +
> +                  assigned_device->msix->total_entries * 16) >>  
> XC_PAGE_SHIFT;
> +            bar_last_pfn = (e_phys + e_size - 1) >> XC_PAGE_SHIFT;
> +
> +            
> cpu_register_physical_memory(assigned_device->msix->mmio_base_addr,
> +                 (assigned_device->msix->total_entries * 16 + XC_PAGE_SIZE - 
> 1)
> +                  & XC_PAGE_MASK,
> +                 assigned_device->msix->mmio_index);
>
> +            if ( assigned_device->msix->table_off )
> +            {
> +                       ret = xc_domain_memory_mapping(xc_handle, domid,
> +                    assigned_device->bases[i].e_physbase >> XC_PAGE_SHIFT,
> +                    assigned_device->bases[i].access.maddr >> XC_PAGE_SHIFT,
> +                    (assigned_device->msix->mmio_base_addr >> XC_PAGE_SHIFT)
> +                    - (assigned_device->bases[i].e_physbase >> 
> XC_PAGE_SHIFT),
> +                    DPCI_ADD_MAPPING);
> +                if ( ret != 0 )
> +                {
> +                    PT_LOG("Error: remove old mapping failed!\n");
> +                    return;

the log message is wrong here: we are trying to create new mappings

> +                }
> +            }
> +            if ( msix_last_pfn != bar_last_pfn )
> +            {
> +                assert(msix_last_pfn < bar_last_pfn);
> +                       ret = xc_domain_memory_mapping(xc_handle, domid,
> +                    msix_last_pfn + 1,
> +                    (assigned_device->bases[i].access.maddr +
> +                     assigned_device->msix->table_off +
> +                     assigned_device->msix->total_entries * 16 +
> +                     XC_PAGE_SIZE -1) >>  XC_PAGE_SHIFT,
> +                    bar_last_pfn - msix_last_pfn,
> +                    DPCI_ADD_MAPPING);
> +                if ( ret != 0 )
> +                {
> +                    PT_LOG("Error: remove old mapping failed!\n");
> +                    return;

same here

> +                }
> +            }
> +               }
> +               else
> +        {
> +                       /* Create new mapping */
> +                       ret = xc_domain_memory_mapping(xc_handle, domid,
>                  assigned_device->bases[i].e_physbase >> XC_PAGE_SHIFT,
>                  assigned_device->bases[i].access.maddr >> XC_PAGE_SHIFT,
>                  (e_size+XC_PAGE_SIZE-1) >> XC_PAGE_SHIFT,
>                  DPCI_ADD_MAPPING);
> 
> -        if ( ret != 0 )
> -        {
> -            PT_LOG("Error: create new mapping failed!\n");
> +            if ( ret != 0 )
> +            {
> +                PT_LOG("Error: create new mapping failed!\n");
> +            }
>          }
> 
> -        ret = remove_msix_mapping(assigned_device, i);
> -        if ( ret != 0 )
> -            PT_LOG("Error: remove MSI-X mmio mapping failed!\n");
> -
>          if ( old_ebase != e_phys && old_ebase != -1 )
>              pt_msix_update_remap(assigned_device, i);
>      }

The two mapping and unmapping big chuncks of code looks very similar
apart from the DPCI_ADD_MAPPING/DPCI_REMOVE_MAPPING parameter.
Could they be refactored into a single function called "change_msix_mappings"?
This is more or less what I have in mind:

change_msix_mappings(assigned_device, DPCI_REMOVE_MAPPING);

update mmio_base_addr

change_msix_mappings(assigned_device, DPCI_ADD_MAPPING);


The rest looks OK to me.

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