On Wed, Jul 30, 2014 at 08:17:02PM +0100, Ard Biesheuvel wrote: > ]On 30 July 2014 13:30, Will Deacon <will.deacon@xxxxxxx> wrote: > > On Wed, Jul 30, 2014 at 11:59:02AM +0100, Ard Biesheuvel wrote: > >> From: Mark Rutland <mark.rutland@xxxxxxx> > >> > >> In certain cases the cpu-release-addr of a CPU may not fall in the > >> linear mapping (e.g. when the kernel is loaded above this address due to > >> the presence of other images in memory). This is problematic for the > >> spin-table code as it assumes that it can trivially convert a > >> cpu-release-addr to a valid VA in the linear map. > >> > >> This patch modifies the spin-table code to use a temporary cached > >> mapping to write to a given cpu-release-addr, enabling us to support > >> addresses regardless of whether they are covered by the linear mapping. > >> > >> Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx> > >> Tested-by: Mark Salter <msalter@xxxxxxxxxx> > >> [ardb: added (__force void *) cast] > >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > >> --- > >> arch/arm64/kernel/smp_spin_table.c | 22 +++++++++++++++++----- > >> 1 file changed, 17 insertions(+), 5 deletions(-) > > > > I'm nervous about this. What if the spin table sits in the same physical 64k > > frame as a read-sensitive device and we're running with 64k pages? > > > > Actually, booting.txt requires cpu-release-addr to point to a > /memreserve/d part of memory, which implies DRAM (or you wouldn't have > to memreserve it) > That means it should always be covered by the linear mapping, unless > it is located before Image in DRAM, which is the case addressed by > this patch. But if it's located before before the Image in DRAM and isn't covered by the linear mapping, then surely the /memreserve/ is pointless too? In which case, this looks like we're simply trying to cater for platforms that aren't following booting.txt (which may need updating if we need to handle this). Will -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
