Re: [PATCH v4] vfio/common: remove spurious tpm-crb-cmd misalignment warning

[Alex Williamson]

On Thu, 28 Apr 2022 15:49:45 +0200
Eric Auger <eric.auger@redhat.com> wrote:

> The CRB command buffer currently is a RAM MemoryRegion and given
> its base address alignment, it causes an error report on
> vfio_listener_region_add(). This region could have been a RAM device
> region, easing the detection of such safe situation but this option
> was not well received. So let's add a helper function that uses the
> memory region owner type to detect the situation is safe wrt
> the assignment. Other device types can be checked here if such kind
> of problem occurs again.
> 
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> Acked-by: Stefan Berger <stefanb@linux.ibm.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> 
> ---
> 
> v3 -> v4:
> - rebase on top of qemu_real_host_page_size() and
>   qemu_real_host_page_size(). Print the size and make the message
>   consistent
> - Added Stefan's A-b and Connie R-b (despite the changes)
> ---
>  hw/vfio/common.c     | 27 ++++++++++++++++++++++++++-
>  hw/vfio/trace-events |  1 +
>  2 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 2b1f78fdfa..f6b9bb6d71 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -40,6 +40,7 @@
>  #include "trace.h"
>  #include "qapi/error.h"
>  #include "migration/migration.h"
> +#include "sysemu/tpm.h"
>  
>  VFIOGroupList vfio_group_list =
>      QLIST_HEAD_INITIALIZER(vfio_group_list);
> @@ -861,6 +862,22 @@ static void 
> vfio_unregister_ram_discard_listener(VFIOContainer *container,
>      g_free(vrdl);
>  }
>  
> +static bool vfio_known_safe_misalignment(MemoryRegionSection *section)
> +{
> +    MemoryRegion *mr = section->mr;
> +
> +    if (!TPM_IS_CRB(mr->owner)) {
> +        return false;
> +    }

It looks like this test is going to need to be wrapped in #ifdef
CONFIG_TPM:

https://gitlab.com/alex.williamson/qemu/-/jobs/2391952412

Thanks,

Alex

> +
> +    /* this is a known safe misaligned region, just trace for debug purpose 
> */
> +    trace_vfio_known_safe_misalignment(memory_region_name(mr),
> +                                       section->offset_within_address_space,
> +                                       section->offset_within_region,
> +                                       qemu_real_host_page_size());
> +    return true;
> +}
> +
>  static void vfio_listener_region_add(MemoryListener *listener,
>                                       MemoryRegionSection *section)
>  {
> @@ -884,7 +901,15 @@ static void vfio_listener_region_add(MemoryListener 
> *listener,
>      if (unlikely((section->offset_within_address_space &
>                    ~qemu_real_host_page_mask()) !=
>                   (section->offset_within_region & 
> ~qemu_real_host_page_mask()))) {
> -        error_report("%s received unaligned region", __func__);
> +        if (!vfio_known_safe_misalignment(section)) {
> +            error_report("%s received unaligned region %s iova=0x%"PRIx64
> +                         " offset_within_region=0x%"PRIx64
> +                         " qemu_real_host_page_size=0x%"PRIxPTR,
> +                         __func__, memory_region_name(section->mr),
> +                         section->offset_within_address_space,
> +                         section->offset_within_region,
> +                         qemu_real_host_page_size());
> +        }
>          return;
>      }
>  
> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> index 0ef1b5f4a6..582882db91 100644
> --- a/hw/vfio/trace-events
> +++ b/hw/vfio/trace-events
> @@ -100,6 +100,7 @@ vfio_listener_region_add_skip(uint64_t start, uint64_t 
> end) "SKIPPING region_add
>  vfio_spapr_group_attach(int groupfd, int tablefd) "Attached groupfd %d to 
> liobn fd %d"
>  vfio_listener_region_add_iommu(uint64_t start, uint64_t end) "region_add 
> [iommu] 0x%"PRIx64" - 0x%"PRIx64
>  vfio_listener_region_add_ram(uint64_t iova_start, uint64_t iova_end, void 
> *vaddr) "region_add [ram] 0x%"PRIx64" - 0x%"PRIx64" [%p]"
> +vfio_known_safe_misalignment(const char *name, uint64_t iova, uint64_t 
> offset_within_region, uintptr_t page_size) "Region \"%s\" iova=0x%"PRIx64" 
> offset_within_region=0x%"PRIx64" qemu_real_host_page_size=0x%"PRIxPTR ": 
> cannot be mapped for DMA"
>  vfio_listener_region_add_no_dma_map(const char *name, uint64_t iova, 
> uint64_t size, uint64_t page_size) "Region \"%s\" 0x%"PRIx64" 
> size=0x%"PRIx64" is not aligned to 0x%"PRIx64" and cannot be mapped for DMA"
>  vfio_listener_region_del_skip(uint64_t start, uint64_t end) "SKIPPING 
> region_del 0x%"PRIx64" - 0x%"PRIx64
>  vfio_listener_region_del(uint64_t start, uint64_t end) "region_del 
> 0x%"PRIx64" - 0x%"PRIx64