Re: [PATCH] MdeModulePkg/BdsDxe: Don't delete "BootNext" until booting it

["Ni, Ruiyu" <ruiyu.ni@intel.com>]

I didn't change the position of code to cache "BootNext", because:
This could avoid the "BootNext" (set by PlatformBootManagerLib) be consumed in *this* boot.

Maybe this time it's more clear.

Thanks/Ray

> -----Original Message-----
> From: Zeng, Star
> Sent: Thursday, September 28, 2017 2:13 PM
> To: Ni, Ruiyu <ruiyu.ni@intel.com>; edk2-devel@lists.01.org
> Cc: Dong, Eric <eric.dong@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: RE: [PATCH] MdeModulePkg/BdsDxe: Don't delete "BootNext" until
> booting it
> 
> The commit log is saying the "BootNext" *DELETED* (before
> PlatformBootManagerLib) may be *LOST* if there is reset during
> PlatformBootManagerLib. I realized it.
> 
> The comment is saying to avoid the "BootNext" "SET" by
> PlatformBootManagerLib. Sorry I am not getting the point.
> 
> Thanks,
> Star
> -----Original Message-----
> From: Ni, Ruiyu
> Sent: Thursday, September 28, 2017 2:02 PM
> To: Zeng, Star <star.zeng@intel.com>; edk2-devel@lists.01.org
> Cc: Dong, Eric <eric.dong@intel.com>
> Subject: RE: [PATCH] MdeModulePkg/BdsDxe: Don't delete "BootNext" until
> booting it
> 
> This could avoid the "BootNext" set by PlatformBootManagerLib be consumed
> in *this* boot.
> 
> If I add "*" around "this", is it more clear?
> 
> Thanks/Ray
> 
> > -----Original Message-----
> > From: Zeng, Star
> > Sent: Thursday, September 28, 2017 2:00 PM
> > To: Ni, Ruiyu <ruiyu.ni@intel.com>; edk2-devel@lists.01.org
> > Cc: Dong, Eric <eric.dong@intel.com>; Zeng, Star <star.zeng@intel.com>
> > Subject: RE: [PATCH] MdeModulePkg/BdsDxe: Don't delete "BootNext"
> > until booting it
> >
> > I am ok with the code logic change, but a little confused by the new
> > comment. It seems not match with the commit log.
> >
> > " This could avoid the "BootNext" set by PlatformBootManagerLib be
> > consumed in this boot. "
> >
> >
> > Thanks,
> > Star
> > -----Original Message-----
> > From: Ni, Ruiyu
> > Sent: Thursday, September 28, 2017 1:50 PM
> > To: edk2-devel@lists.01.org
> > Cc: Dong, Eric <eric.dong@intel.com>; Zeng, Star <star.zeng@intel.com>
> > Subject: [PATCH] MdeModulePkg/BdsDxe: Don't delete "BootNext" until
> > booting it
> >
> > Current implementation deletes the "BootNext" before calling any
> > PlatformBootManagerLib APIs, but if system resets in
> > PlatformBootManagerLib APIs, "BootNext" is not consumed but lost.
> >
> > The patch defers the deletion of "BootNext" to before booting it.
> >
> > Contributed-under: TianoCore Contribution Agreement 1.0
> > Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
> > Cc: Eric Dong <eric.dong@intel.com>
> > Cc: Star Zeng <star.zeng@intel.com>
> > ---
> >  MdeModulePkg/Universal/BdsDxe/BdsEntry.c | 35
> > ++++++++++++++++++--------
> > ------
> >  1 file changed, 20 insertions(+), 15 deletions(-)
> >
> > diff --git a/MdeModulePkg/Universal/BdsDxe/BdsEntry.c
> > b/MdeModulePkg/Universal/BdsDxe/BdsEntry.c
> > index ac5f9088dd..a6fe617b56 100644
> > --- a/MdeModulePkg/Universal/BdsDxe/BdsEntry.c
> > +++ b/MdeModulePkg/Universal/BdsDxe/BdsEntry.c
> > @@ -808,7 +808,8 @@ BdsEntry (
> >    ASSERT_EFI_ERROR (Status);
> >
> >    //
> > -  // Cache and remove the "BootNext" NV variable.
> > +  // Cache the "BootNext" NV variable before calling any
> > + PlatformBootManagerLib APIs  // This could avoid the "BootNext" set
> > + by
> > PlatformBootManagerLib be consumed in this boot.
> >    //
> >    GetEfiGlobalVariable2 (EFI_BOOT_NEXT_VARIABLE_NAME, (VOID **)
> > &BootNext, &DataSize);
> >    if (DataSize != sizeof (UINT16)) {
> > @@ -817,17 +818,6 @@ BdsEntry (
> >      }
> >      BootNext = NULL;
> >    }
> > -  Status = gRT->SetVariable (
> > -                  EFI_BOOT_NEXT_VARIABLE_NAME,
> > -                  &gEfiGlobalVariableGuid,
> > -                  0,
> > -                  0,
> > -                  NULL
> > -                  );
> > -  //
> > -  // Deleting NV variable shouldn't fail unless it doesn't exist.
> > -  //
> > -  ASSERT (Status == EFI_SUCCESS || Status == EFI_NOT_FOUND);
> >
> >    //
> >    // Initialize the platform language variables @@ -1052,10 +1042,25
> > @@ BdsEntry (
> >
> >      EfiBootManagerHotkeyBoot ();
> >
> > -    //
> > -    // Boot to "BootNext"
> > -    //
> >      if (BootNext != NULL) {
> > +      //
> > +      // Delete "BootNext" NV variable before transferring control to
> > + it to
> > prevent loops.
> > +      //
> > +      Status = gRT->SetVariable (
> > +                      EFI_BOOT_NEXT_VARIABLE_NAME,
> > +                      &gEfiGlobalVariableGuid,
> > +                      0,
> > +                      0,
> > +                      NULL
> > +                      );
> > +      //
> > +      // Deleting NV variable shouldn't fail unless it doesn't exist.
> > +      //
> > +      ASSERT (Status == EFI_SUCCESS || Status == EFI_NOT_FOUND);
> > +
> > +      //
> > +      // Boot to "BootNext"
> > +      //
> >        UnicodeSPrint (BootNextVariableName, sizeof
> > (BootNextVariableName), L"Boot%04x", *BootNext);
> >        Status = EfiBootManagerVariableToLoadOption
> > (BootNextVariableName, &LoadOption);
> >        if (!EFI_ERROR (Status)) {
> > --
> > 2.12.2.windows.2