On Mon, 12 Dec 2022, Julien Grall wrote: > From: Julien Grall <jgr...@amazon.com> > > At the moment, enable_mmu() will return to an address in the 1:1 mapping > and each path is responsible to switch to the runtime mapping. > > In a follow-up patch, the behavior to switch to the runtime mapping > will become more complex. So to avoid more code/comment duplication, > move the switch in enable_mmu(). > > Lastly, take the opportunity to replace load from literal pool with > mov_w. > > Signed-off-by: Julien Grall <jgr...@amazon.com>
Reviewed-by: Stefano Stabellini <sstabell...@kernel.org> > --- > Changes in v3: > - Fix typo in the commit message > > Changes in v2: > - Patch added > --- > xen/arch/arm/arm32/head.S | 50 +++++++++++++++++++++++---------------- > 1 file changed, 30 insertions(+), 20 deletions(-) > > diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S > index ce680be91be1..40c1d7502007 100644 > --- a/xen/arch/arm/arm32/head.S > +++ b/xen/arch/arm/arm32/head.S > @@ -167,19 +167,11 @@ past_zImage: > bl check_cpu_mode > bl cpu_init > bl create_page_tables > - bl enable_mmu > > - /* We are still in the 1:1 mapping. Jump to the runtime Virtual > Address. */ > - mov_w r0, primary_switched > - mov pc, r0 > + /* Address in the runtime mapping to jump to after the MMU is > enabled */ > + mov_w lr, primary_switched > + b enable_mmu > primary_switched: > - /* > - * The 1:1 map may clash with other parts of the Xen virtual memory > - * layout. As it is not used anymore, remove it completely to > - * avoid having to worry about replacing existing mapping > - * afterwards. > - */ > - bl remove_identity_mapping > bl setup_fixmap > #ifdef CONFIG_EARLY_PRINTK > /* Use a virtual address to access the UART. */ > @@ -223,12 +215,10 @@ GLOBAL(init_secondary) > bl check_cpu_mode > bl cpu_init > bl create_page_tables > - bl enable_mmu > > - > - /* We are still in the 1:1 mapping. Jump to the runtime Virtual > Address. */ > - mov_w r0, secondary_switched > - mov pc, r0 > + /* Address in the runtime mapping to jump to after the MMU is > enabled */ > + mov_w lr, secondary_switched > + b enable_mmu > secondary_switched: > /* > * Non-boot CPUs need to move on to the proper pagetables, which were > @@ -523,9 +513,12 @@ virtphys_clash: > ENDPROC(create_page_tables) > > /* > - * Turn on the Data Cache and the MMU. The function will return on the 1:1 > - * mapping. In other word, the caller is responsible to switch to the runtime > - * mapping. > + * Turn on the Data Cache and the MMU. The function will return > + * to the virtual address provided in LR (e.g. the runtime mapping). > + * > + * Inputs: > + * r9 : paddr(start) > + * lr : Virtual address to return to > * > * Clobbers r0 - r3 > */ > @@ -551,7 +544,24 @@ enable_mmu: > dsb /* Flush PTE writes and finish reads */ > mcr CP32(r0, HSCTLR) /* now paging is enabled */ > isb /* Now, flush the icache */ > - mov pc, lr > + > + /* > + * The MMU is turned on and we are in the 1:1 mapping. Switch > + * to the runtime mapping. > + */ > + mov_w r0, 1f > + mov pc, r0 > +1: > + /* > + * The 1:1 map may clash with other parts of the Xen virtual memory > + * layout. As it is not used anymore, remove it completely to > + * avoid having to worry about replacing existing mapping > + * afterwards. > + * > + * On return this will jump to the virtual address requested by > + * the caller. > + */ > + b remove_identity_mapping > ENDPROC(enable_mmu) > > /* > -- > 2.38.1 >
