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Date: Tue, 12 Apr 2011 10:40:57 -0700
From: Yinghai Lu <yinghai@...nel.org>
To: stefano.stabellini@...citrix.com
CC: linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
konrad.wilk@...cle.com, jeremy@...p.org, hpa@...ux.intel.com,
mingo@...e.hu, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 2/4] x86,xen: introduce x86_init.mapping.pagetable_reserve
On 04/12/2011 04:19 AM, stefano.stabellini@...citrix.com wrote:
> From: Stefano Stabellini<stefano.stabellini@...citrix.com>
>
> Introduce a new x86_init hook called pagetable_reserve that during the
> initial memory mapping is used to reserve a range of memory addresses for
> kernel pagetable usage.
>
> On native it just calls memblock_x86_reserve_range while on xen it also
> takes care of setting the spare memory previously allocated
> for kernel pagetable pages from RO to RW, so that it can be used for
> other purposes.
>
> Signed-off-by: Stefano Stabellini<stefano.stabellini@...citrix.com>
> Cc: Yinghai Lu<yinghai@...nel.org>
> Cc: H. Peter Anvin<hpa@...or.com>
> Cc: Ingo Molnar<mingo@...e.hu>
Acked-by: Yinghai Lu <yinghai@...nel.org>
> ---
> arch/x86/include/asm/pgtable_types.h | 1 +
> arch/x86/include/asm/x86_init.h | 9 +++++++++
> arch/x86/kernel/x86_init.c | 4 ++++
> arch/x86/mm/init.c | 9 +++++++--
> arch/x86/xen/mmu.c | 15 +++++++++++++++
> 5 files changed, 36 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
> index 7db7723..d56187c 100644
> --- a/arch/x86/include/asm/pgtable_types.h
> +++ b/arch/x86/include/asm/pgtable_types.h
> @@ -299,6 +299,7 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
> /* Install a pte for a particular vaddr in kernel space. */
> void set_pte_vaddr(unsigned long vaddr, pte_t pte);
>
> +extern void native_pagetable_reserve(u64 start, u64 end);
> #ifdef CONFIG_X86_32
> extern void native_pagetable_setup_start(pgd_t *base);
> extern void native_pagetable_setup_done(pgd_t *base);
> diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
> index 643ebf2..d66b3a2 100644
> --- a/arch/x86/include/asm/x86_init.h
> +++ b/arch/x86/include/asm/x86_init.h
> @@ -68,6 +68,14 @@ struct x86_init_oem {
> };
>
> /**
> + * struct x86_init_mapping - platform specific initial kernel pagetable setup
> + * @pagetable_reserve: reserve a range of addresses for kernel pagetable usage
> + */
> +struct x86_init_mapping {
> + void (*pagetable_reserve)(u64 start, u64 end);
> +};
> +
> +/**
> * struct x86_init_paging - platform specific paging functions
> * @pagetable_setup_start: platform specific pre paging_init() call
> * @pagetable_setup_done: platform specific post paging_init() call
> @@ -123,6 +131,7 @@ struct x86_init_ops {
> struct x86_init_mpparse mpparse;
> struct x86_init_irqs irqs;
> struct x86_init_oem oem;
> + struct x86_init_mapping mapping;
> struct x86_init_paging paging;
> struct x86_init_timers timers;
> struct x86_init_iommu iommu;
> diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
> index c11514e..75ef4b1 100644
> --- a/arch/x86/kernel/x86_init.c
> +++ b/arch/x86/kernel/x86_init.c
> @@ -61,6 +61,10 @@ struct x86_init_ops x86_init __initdata = {
> .banner = default_banner,
> },
>
> + .mapping = {
> + .pagetable_reserve = native_pagetable_reserve,
> + },
> +
> .paging = {
> .pagetable_setup_start = native_pagetable_setup_start,
> .pagetable_setup_done = native_pagetable_setup_done,
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index 286d289..ed0650b 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -81,6 +81,11 @@ static void __init find_early_table_space(unsigned long end, int use_pse,
> end, pgt_buf_start<< PAGE_SHIFT, pgt_buf_top<< PAGE_SHIFT);
> }
>
> +void native_pagetable_reserve(u64 start, u64 end)
> +{
> + memblock_x86_reserve_range(start, end, "PGTABLE");
> +}
> +
> struct map_range {
> unsigned long start;
> unsigned long end;
> @@ -273,8 +278,8 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
> __flush_tlb_all();
>
> if (!after_bootmem&& pgt_buf_end> pgt_buf_start)
> - memblock_x86_reserve_range(pgt_buf_start<< PAGE_SHIFT,
> - pgt_buf_end<< PAGE_SHIFT, "PGTABLE");
> + x86_init.mapping.pagetable_reserve(PFN_PHYS(pgt_buf_start),
> + PFN_PHYS(pgt_buf_end));
>
> if (!after_bootmem)
> early_memtest(start, end);
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index 6b833db..fec8680 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -1275,6 +1275,20 @@ static __init void xen_pagetable_setup_start(pgd_t *base)
> {
> }
>
> +static __init void xen_mapping_pagetable_reserve(u64 start, u64 end)
> +{
> + /* reserve the range used */
> + memblock_x86_reserve_range(start, end, "PGTABLE");
> +
> + /* set as RW the rest */
> + printk(KERN_DEBUG "xen: setting RW the range %llx - %llx\n", end,
> + PFN_PHYS(pgt_buf_top));
> + while (end< PFN_PHYS(pgt_buf_top)) {
> + make_lowmem_page_readwrite(__va(end));
> + end += PAGE_SIZE;
> + }
> +}
> +
it would be more cleaner to xen code if you make mark start/end to RO, and not make them all before as RO.
Thanks
Yinghai Lu
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