Description

I was doing some SDK testing on an arm64 machine. I had installed the 6.0.2 x64 runtime and arm64 sdk/runtime. MU then updated my arm64 runtime to 6.0.3.

dotnet new wpf
dotnet publish -r win-x64 --no-self-contained
set DOTNET_ROOT_X64=c:\Program Files\dotnet\x64
cd bin\Debug\net6.0-windows\win-x64\publish
test.exe

Reproduction Steps

Install arm64 sdk and x64 runtime.
Install a newer arm64 runtime.

dotnet new wpf
dotnet publish -r win-x64 --no-self-contained
set DOTNET_ROOT_X64=c:\Program Files\dotnet\x64
cd bin\Debug\net6.0-windows\win-x64\publish
test.exe

Expected behavior

The application should launch

Actual behavior

Attempting FX roll forward starting from version='[6.0.0]', apply_patches=1, version_compatibility_range=minor, roll_to_highest_version=0, prefer_release=1
'Roll forward' enabled with version_compatibility_range [minor]. Looking for the lowest release greater than or equal version to [6.0.0]
Found version [6.0.2]
Applying patch roll forward from [6.0.2] on release only
Inspecting version... [6.0.3]
Inspecting version... [6.0.2]
Changing Selected FX version from [c:\Program Files\dotnet\x64\shared\Microsoft.NETCore.App\6.0.2] to [C:\Program Files\dotnet\shared\Microsoft.NETCore.App\6.0.3]
Chose FX version [C:\Program Files\dotnet\shared\Microsoft.NETCore.App\6.0.3]

App then fails to launch as it's trying to use the arm64 hostfxr now instead of x64 like it's supposed to.

Regression?

No

Known Workarounds

set DOTNET_MULTILEVEL_LOOKUP=0

or install a newer x64 runtime

Configuration

This was an arm64 machine with a 6.0.2 runtime and 6.0.300 SDK.

Other information

According to Vitek and Andy, it could be we need to downport this fix: #59890