From fce0d5740322b98b863f9e609f5a9bd4c06703af Mon Sep 17 00:00:00 2001 From: R Sharada Date: Sat, 25 Jun 2005 14:58:10 -0700 Subject: [PATCH] ppc64: kexec support for ppc64 This patch implements the kexec support for ppc64 platforms. A couple of notes: 1) We copy the pages in virtual mode, using the full base kernel and a statically allocated stack. At kexec_prepare time we scan the pages and if any overlap our (0, _end[]) range we return -ETXTBSY. On PowerPC 64 systems running in LPAR (logical partitioning) mode, only a small region of memory, referred to as the RMO, can be accessed in real mode. Since Linux runs with only one zone of memory in the memory allocator, and it can be orders of magnitude more memory than the RMO, looping until we allocate pages in the source region is not feasible. Copying in virtual means we don't have to write a hash table generation and call hypervisor to insert translations, instead we rely on the pinned kernel linear mapping. The kernel already has move to linked location built in, so there is no requirement to load it at 0. If we want to load something other than a kernel, then a stub can be written to copy a linear chunk in real mode. 2) The start entry point gets passed parameters from the kernel. Slaves are started at a fixed address after copying code from the entry point. All CPUs get passed their firmware assigned physical id in r3 (most calling conventions use this register for the first argument). This is used to distinguish each CPU from all other CPUs. Since firmware is not around, there is no other way to obtain this information other than to pass it somewhere. A single CPU, referred to here as the master and the one executing the kexec call, branches to start with the address of start in r4. While this can be calculated, we have to load it through a gpr to branch to this point so defining the register this is contained in is free. A stack of unspecified size is available at r1 (also common calling convention). All remaining running CPUs are sent to start at absolute address 0x60 after copying the first 0x100 bytes from start to address 0. This convention was chosen because it matches what the kernel has been doing itself. (only gpr3 is defined). Note: This is not quite the convention of the kexec bootblock v2 in the kernel. A stub has been written to convert between them, and we may adjust the kernel in the future to allow this directly without any stub. 3) Destination pages can be placed anywhere, even where they would not be accessible in real mode. This will allow us to place ram disks above the RMO if we choose. Signed-off-by: Milton Miller Signed-off-by: R Sharada Signed-off-by: Paul Mackerras Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/ppc64/kernel/head.S | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'arch/ppc64/kernel/head.S') diff --git a/arch/ppc64/kernel/head.S b/arch/ppc64/kernel/head.S index 02c8f4e..675c270 100644 --- a/arch/ppc64/kernel/head.S +++ b/arch/ppc64/kernel/head.S @@ -1194,7 +1194,7 @@ _GLOBAL(pSeries_secondary_smp_init) bl .__restore_cpu_setup /* Set up a paca value for this processor. Since we have the - * physical cpu id in r3, we need to search the pacas to find + * physical cpu id in r24, we need to search the pacas to find * which logical id maps to our physical one. */ LOADADDR(r13, paca) /* Get base vaddr of paca array */ @@ -1207,8 +1207,8 @@ _GLOBAL(pSeries_secondary_smp_init) cmpwi r5,NR_CPUS blt 1b -99: HMT_LOW /* Couldn't find our CPU id */ - b 99b + mr r3,r24 /* not found, copy phys to r3 */ + b .kexec_wait /* next kernel might do better */ 2: mtspr SPRG3,r13 /* Save vaddr of paca in SPRG3 */ /* From now on, r24 is expected to be logica cpuid */ -- cgit v1.1