Re: [edk2-devel] [PATCH v5 22/35] OvmfPkg/XenPlatformPei: no hvmloader: get the E820 table via hypercall

["Laszlo Ersek" <lersek@redhat.com>]

On 08/13/19 13:31, Anthony PERARD wrote:
> When the Xen PVH entry point has been used, hvmloader hasn't run and
> hasn't prepared an E820 table. The only way left to get an E820 table
> is to ask Xen via an hypercall.  We keep the result cached to avoid
> making a second hypercall which would give the same result.
> 
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1689
> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
> Acked-by: Laszlo Ersek <lersek@redhat.com>
> ---
> 
> Notes:
>     v5:
>     - fix commit message, the hypercall *can* be made several time, but we
>       still cache the result.

Addresses Roger's feedback in:

http://mid.mail-archive.com/20190808104558.vm6dfic5dntjsnt4@Air-de-Roger
https://edk2.groups.io/g/devel/message/45160

My ACK stands.

Thanks
Laszlo


>     v3:
>     - fix commit message
>     - add 'm' prefix to the global variables
>       and make them static
> 
>  OvmfPkg/XenPlatformPei/Xen.c | 46 +++++++++++++++++++++++++++++++++++-
>  1 file changed, 45 insertions(+), 1 deletion(-)
> 
> diff --git a/OvmfPkg/XenPlatformPei/Xen.c b/OvmfPkg/XenPlatformPei/Xen.c
> index f26f0e56dd..72f6f37b46 100644
> --- a/OvmfPkg/XenPlatformPei/Xen.c
> +++ b/OvmfPkg/XenPlatformPei/Xen.c
> @@ -27,6 +27,7 @@
>  #include <Library/MtrrLib.h>
>  #include <IndustryStandard/Xen/arch-x86/hvm/start_info.h>
>  #include <Library/XenHypercallLib.h>
> +#include <IndustryStandard/Xen/memory.h>
>  
>  #include "Platform.h"
>  #include "Xen.h"
> @@ -40,6 +41,8 @@ EFI_XEN_INFO mXenInfo;
>  // Only the E820 table is used by OVMF.
>  //
>  EFI_XEN_OVMF_INFO *mXenHvmloaderInfo;
> +STATIC EFI_E820_ENTRY64 mE820Entries[128];
> +STATIC UINT32 mE820EntriesCount;
>  
>  /**
>    Returns E820 map provided by Xen
> @@ -55,6 +58,12 @@ XenGetE820Map (
>    UINT32 *Count
>    )
>  {
> +  INTN ReturnCode;
> +  xen_memory_map_t Parameters;
> +  UINTN LoopIndex;
> +  UINTN Index;
> +  EFI_E820_ENTRY64 TmpEntry;
> +
>    //
>    // Get E820 produced by hvmloader
>    //
> @@ -66,7 +75,42 @@ XenGetE820Map (
>      return EFI_SUCCESS;
>    }
>  
> -  return EFI_NOT_FOUND;
> +  //
> +  // Otherwise, get the E820 table from the Xen hypervisor
> +  //
> +
> +  if (mE820EntriesCount > 0) {
> +    *Entries = mE820Entries;
> +    *Count = mE820EntriesCount;
> +    return EFI_SUCCESS;
> +  }
> +
> +  Parameters.nr_entries = 128;
> +  set_xen_guest_handle (Parameters.buffer, mE820Entries);
> +
> +  // Returns a errno
> +  ReturnCode = XenHypercallMemoryOp (XENMEM_memory_map, &Parameters);
> +  ASSERT (ReturnCode == 0);
> +
> +  mE820EntriesCount = Parameters.nr_entries;
> +
> +  //
> +  // Sort E820 entries
> +  //
> +  for (LoopIndex = 1; LoopIndex < mE820EntriesCount; LoopIndex++) {
> +    for (Index = LoopIndex; Index < mE820EntriesCount; Index++) {
> +      if (mE820Entries[Index - 1].BaseAddr > mE820Entries[Index].BaseAddr) {
> +        TmpEntry = mE820Entries[Index];
> +        mE820Entries[Index] = mE820Entries[Index - 1];
> +        mE820Entries[Index - 1] = TmpEntry;
> +      }
> +    }
> +  }
> +
> +  *Count = mE820EntriesCount;
> +  *Entries = mE820Entries;
> +
> +  return EFI_SUCCESS;
>  }
>  
>  /**
>