1. 20 Jun, 2022 6 commits
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  4. 17 Jun, 2022 1 commit
    • Kirill A. Shutemov's avatar
      x86/tdx: Handle load_unaligned_zeropad() page-cross to a shared page · 1e776965
      Kirill A. Shutemov authored
      load_unaligned_zeropad() can lead to unwanted loads across page boundaries.
      The unwanted loads are typically harmless. But, they might be made to
      totally unrelated or even unmapped memory. load_unaligned_zeropad()
      relies on exception fixup (#PF, #GP and now #VE) to recover from these
      unwanted loads.
      
      In TDX guests, the second page can be shared page and a VMM may configure
      it to trigger #VE.
      
      The kernel assumes that #VE on a shared page is an MMIO access and tries to
      decode instruction to handle it. In case of load_unaligned_zeropad() it
      may result in confusion as it is not MMIO access.
      
      Fix it by detecting split page MMIO accesses and failing them.
      load_unaligned_zeropad() will recover using exception fixups.
      
      The issue was discovered by analysis and reproduced artificially. It was
      not triggered during testing.
      
      [ dhansen: fix up changelogs and comments for grammar and clarity,
      	   plus incorporate Kirill's off-by-one fix]
      Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
      Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
      Link: https://lkml.kernel.org/r/20220614120135.14812-4-kirill.shutemov@linux.intel.com
      1e776965