| Message ID | 20190722213958.5761-16-julien.grall@arm.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xen/arm: Rework head.S to make it more compliant with the Arm Arm | expand |
On Mon, 22 Jul 2019, Julien Grall wrote: > At the moment, the fixmap table is only hooked when earlyprintk is used. > This is fine today because in C land, the fixmap is not used by anyone > until the the boot CPU is switching to the runtime page-tables. > > In the future, the boot CPU will not switch between page-tables to > avoid TLB incoherency. Thus, the fixmap table will need to be always > hooked beofre any use. Let's start doing it now in setup_fixmap(). ^ before Assuming you fix the typo: Acked-by: Stefano Stabellini <sstabellini@kernel.org> > Lastly, document the behavior and the main registers usage within the > function. > > Signed-off-by: Julien Grall <julien.grall@arm.com> > > --- > Changes in v2: > - Update the comment to reflect that we clobbers x1 - x4 and not > x0 - x1. > - Add the list of input registers > - s/ID map/1:1 mapping/ > - Reword the commit message > --- > xen/arch/arm/arm64/head.S | 18 ++++++++++++++++-- > 1 file changed, 16 insertions(+), 2 deletions(-) > > diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S > index a607b3bdb1..f165dd61ca 100644 > --- a/xen/arch/arm/arm64/head.S > +++ b/xen/arch/arm/arm64/head.S > @@ -693,8 +693,21 @@ identity_mapping_removed: > ret > ENDPROC(remove_identity_mapping) > > +/* > + * Map the UART in the fixmap (when earlyprintk is used) and hook the > + * fixmap table in the page tables. > + * > + * The fixmap cannot be mapped in create_page_tables because it may > + * clash with the 1:1 mapping. > + * > + * Inputs: > + * x20: Physical offset > + * x23: Early UART base physical address > + * > + * Clobbers x1 - x4 > + */ > setup_fixmap: > -#if defined(CONFIG_EARLY_PRINTK) /* Fixmap is only used by early printk */ > +#ifdef CONFIG_EARLY_PRINTK > /* Add UART to the fixmap table */ > ldr x1, =xen_fixmap /* x1 := vaddr (xen_fixmap) */ > lsr x2, x23, #THIRD_SHIFT > @@ -702,6 +715,7 @@ setup_fixmap: > mov x3, #PT_DEV_L3 > orr x2, x2, x3 /* x2 := 4K dev map including UART */ > str x2, [x1, #(FIXMAP_CONSOLE*8)] /* Map it in the first fixmap's slot */ > +#endif > > /* Map fixmap into boot_second */ > ldr x4, =boot_second /* x4 := vaddr (boot_second) */ > @@ -714,7 +728,7 @@ setup_fixmap: > > /* Ensure any page table updates made above have occurred. */ > dsb nshst > -#endif > + > ret > ENDPROC(setup_fixmap) > > -- > 2.11.0 >
diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S index a607b3bdb1..f165dd61ca 100644 --- a/xen/arch/arm/arm64/head.S +++ b/xen/arch/arm/arm64/head.S @@ -693,8 +693,21 @@ identity_mapping_removed: ret ENDPROC(remove_identity_mapping) +/* + * Map the UART in the fixmap (when earlyprintk is used) and hook the + * fixmap table in the page tables. + * + * The fixmap cannot be mapped in create_page_tables because it may + * clash with the 1:1 mapping. + * + * Inputs: + * x20: Physical offset + * x23: Early UART base physical address + * + * Clobbers x1 - x4 + */ setup_fixmap: -#if defined(CONFIG_EARLY_PRINTK) /* Fixmap is only used by early printk */ +#ifdef CONFIG_EARLY_PRINTK /* Add UART to the fixmap table */ ldr x1, =xen_fixmap /* x1 := vaddr (xen_fixmap) */ lsr x2, x23, #THIRD_SHIFT @@ -702,6 +715,7 @@ setup_fixmap: mov x3, #PT_DEV_L3 orr x2, x2, x3 /* x2 := 4K dev map including UART */ str x2, [x1, #(FIXMAP_CONSOLE*8)] /* Map it in the first fixmap's slot */ +#endif /* Map fixmap into boot_second */ ldr x4, =boot_second /* x4 := vaddr (boot_second) */ @@ -714,7 +728,7 @@ setup_fixmap: /* Ensure any page table updates made above have occurred. */ dsb nshst -#endif + ret ENDPROC(setup_fixmap)
At the moment, the fixmap table is only hooked when earlyprintk is used. This is fine today because in C land, the fixmap is not used by anyone until the the boot CPU is switching to the runtime page-tables. In the future, the boot CPU will not switch between page-tables to avoid TLB incoherency. Thus, the fixmap table will need to be always hooked beofre any use. Let's start doing it now in setup_fixmap(). Lastly, document the behavior and the main registers usage within the function. Signed-off-by: Julien Grall <julien.grall@arm.com> --- Changes in v2: - Update the comment to reflect that we clobbers x1 - x4 and not x0 - x1. - Add the list of input registers - s/ID map/1:1 mapping/ - Reword the commit message --- xen/arch/arm/arm64/head.S | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)