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? > I see what you mean. This is potentially hairy, as EFI already ioremap_cache()s everything known to it as normal DRAM, so using plain ioremap() here if pfn_valid() returns false for cpu-release-addr's PFN may still result in mappings with different attributes for the same region. So how should we decide whether to call ioremap() or ioremap_cache() in this case? -- Ard. -- 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
