On Tue, 2014-07-29 at 12:49 +0200, 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>
> ---
> arch/arm64/kernel/smp_spin_table.c | 21 ++++++++++++++++-----
> 1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/kernel/smp_spin_table.c b/arch/arm64/kernel/smp_spin_table.c
> index 0347d38eea29..70181c1bf42d 100644
> --- a/arch/arm64/kernel/smp_spin_table.c
> +++ b/arch/arm64/kernel/smp_spin_table.c
> @@ -20,6 +20,7 @@
> #include <linux/init.h>
> #include <linux/of.h>
> #include <linux/smp.h>
> +#include <linux/types.h>
>
> #include <asm/cacheflush.h>
> #include <asm/cpu_ops.h>
> @@ -65,12 +66,21 @@ static int smp_spin_table_cpu_init(struct device_node *dn, unsigned int cpu)
>
> static int smp_spin_table_cpu_prepare(unsigned int cpu)
> {
> - void **release_addr;
> + __le64 __iomem *release_addr;
>
> if (!cpu_release_addr[cpu])
> return -ENODEV;
>
> - release_addr = __va(cpu_release_addr[cpu]);
> + /*
> + * The cpu-release-addr may or may not be inside the linear mapping.
> + * As ioremap_cache will either give us a new mapping or reuse the
> + * existing linear mapping, we can use it to cover both cases. In
> + * either case the memory will be MT_NORMAL.
> + */
> + release_addr = ioremap_cache(cpu_release_addr[cpu],
> + sizeof(*release_addr));
> + if (!release_addr)
> + return -ENOMEM;
>
> /*
> * We write the release address as LE regardless of the native
> @@ -79,15 +89,16 @@ static int smp_spin_table_cpu_prepare(unsigned int cpu)
> * boot-loader's endianess before jumping. This is mandated by
> * the boot protocol.
> */
> - release_addr[0] = (void *) cpu_to_le64(__pa(secondary_holding_pen));
> -
> - __flush_dcache_area(release_addr, sizeof(release_addr[0]));
> + writeq_relaxed(__pa(secondary_holding_pen), release_addr);
> + __flush_dcache_area(release_addr, sizeof(*release_addr));
__flush_dcache_area((__force void *)release_addr, ...
to avoid sparse warning.
>
> /*
> * Send an event to wake up the secondary CPU.
> */
> sev();
>
> + iounmap(release_addr);
> +
> return 0;
> }
>
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