On Fri, 7 Dec 2018 at 11:43, Ard Biesheuvel <[email protected]> wrote: > > On Fri, 7 Dec 2018 at 11:41, Laszlo Ersek <[email protected]> wrote: > > > > On 12/06/18 22:37, Ard Biesheuvel wrote: > > > This reverts commit 82379bf6603274e81604d5a6f6bb14bdde616286. > > > > > > On AArch64, we can only use 48 address bits while running in UEFI, > > > while the GCD and UEFI memory maps may describe up to 52 bits of > > > physical address space. For this reason, MAX_ADDRESS was reduced > > > to 48 bits, to ensure that the firmware does not inadvertently > > > attempt to allocate memory that we cannot access. > > > > > > However, MAX_ADDRESS is used in runtime drivers as well, and > > > runtime drivers may deal with kernel virtual addresses, which have > > > bits [63:48] set. In fact, the OS may be running with 64 KB pages > > > and pass addresses into the runtime services that use up to 52 > > > bits of address space, either with the top bits set or cleared, > > > even if the physical address space does not extend beyond 48 bits. > > > > > > In summary, changing MAX_ADDRESS is a mistake, and needs to be > > > reverted. > > > > > > Cc: Leif Lindholm <[email protected]> > > > Cc: Liming Gao <[email protected]> > > > Cc: Laszlo Ersek <[email protected]> > > > Cc: Eric Auger <[email protected]> > > > Cc: Andrew Jones <[email protected]> > > > Cc: Philippe Mathieu-Daude <[email protected]> > > > Contributed-under: TianoCore Contribution Agreement 1.1 > > > Signed-off-by: Ard Biesheuvel <[email protected]> > > > --- > > > MdePkg/Include/AArch64/ProcessorBind.h | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/MdePkg/Include/AArch64/ProcessorBind.h > > > b/MdePkg/Include/AArch64/ProcessorBind.h > > > index dad75df1c579..968c18f915ae 100644 > > > --- a/MdePkg/Include/AArch64/ProcessorBind.h > > > +++ b/MdePkg/Include/AArch64/ProcessorBind.h > > > @@ -138,9 +138,9 @@ typedef INT64 INTN; > > > #define MAX_2_BITS 0xC000000000000000ULL > > > > > > /// > > > -/// Maximum legal AARCH64 address (48 bits for 4 KB page size) > > > +/// Maximum legal AARCH64 address > > > /// > > > -#define MAX_ADDRESS 0xFFFFFFFFFFFFULL > > > +#define MAX_ADDRESS 0xFFFFFFFFFFFFFFFFULL > > > > > > /// > > > /// Maximum legal AArch64 INTN and UINTN values. > > > > > > > I was worried the patch could regress some things, but unfortunately, I > > couldn't name any specific area of concern. Sorry about that. > > > > Sometimes a hunch should be taken more seriously, I suppose :-) > > > For this change: > > > > Reviewed-by: Laszlo Ersek <[email protected]> > > >
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