[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v3 18/19] xen/arm: mm: Rework setup_xenheap_mappings()
On Mon, 21 Feb 2022, Julien Grall wrote: > From: Julien Grall <julien.grall@xxxxxxx> > > The current implementation of setup_xenheap_mappings() is using 1GB > mappings. This can lead to unexpected result because the mapping > may alias a non-cachable region (such as device or reserved regions). > For more details see B2.8 in ARM DDI 0487H.a. > > map_pages_to_xen() was recently reworked to allow superpage mappings, > support contiguous mapping and deal with the use of pagge-tables before pagetables > they are mapped. > > Most of the code in setup_xenheap_mappings() is now replaced with a > single call to map_pages_to_xen(). > > Signed-off-by: Julien Grall <julien.grall@xxxxxxx> > Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx> > > --- > Changes in v3: > - Don't use 1GB mapping > - Re-order code in setup_mm() in a separate patch > > Changes in v2: > - New patch > --- > xen/arch/arm/mm.c | 87 ++++++++++------------------------------------- > 1 file changed, 18 insertions(+), 69 deletions(-) Very good! > diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c > index 11b6b60a2bc1..4af59375d998 100644 > --- a/xen/arch/arm/mm.c > +++ b/xen/arch/arm/mm.c > @@ -138,17 +138,6 @@ static DEFINE_PAGE_TABLE(cpu0_pgtable); > static DEFINE_PAGE_TABLES(cpu0_dommap, DOMHEAP_SECOND_PAGES); > #endif > > -#ifdef CONFIG_ARM_64 > -/* The first page of the first level mapping of the xenheap. The > - * subsequent xenheap first level pages are dynamically allocated, but > - * we need this one to bootstrap ourselves. */ > -static DEFINE_PAGE_TABLE(xenheap_first_first); > -/* The zeroeth level slot which uses xenheap_first_first. Used because > - * setup_xenheap_mappings otherwise relies on mfn_to_virt which isn't > - * valid for a non-xenheap mapping. */ > -static __initdata int xenheap_first_first_slot = -1; > -#endif > - > /* Common pagetable leaves */ > /* Second level page tables. > * > @@ -815,77 +804,37 @@ void __init setup_xenheap_mappings(unsigned long > base_mfn, > void __init setup_xenheap_mappings(unsigned long base_mfn, > unsigned long nr_mfns) > { > - lpae_t *first, pte; > - unsigned long mfn, end_mfn; > - vaddr_t vaddr; > - > - /* Align to previous 1GB boundary */ > - mfn = base_mfn & ~((FIRST_SIZE>>PAGE_SHIFT)-1); > + int rc; > > /* First call sets the xenheap physical and virtual offset. */ > if ( mfn_eq(xenheap_mfn_start, INVALID_MFN) ) > { > + unsigned long mfn_gb = base_mfn & ~((FIRST_SIZE >> PAGE_SHIFT) - 1); > + > xenheap_mfn_start = _mfn(base_mfn); > xenheap_base_pdx = mfn_to_pdx(_mfn(base_mfn)); > + /* > + * The base address may not be aligned to the first level > + * size (e.g. 1GB when using 4KB pages). This would prevent > + * superpage mappings for all the regions because the virtual > + * address and machine address should both be suitably aligned. > + * > + * Prevent that by offsetting the start of the xenheap virtual > + * address. > + */ > xenheap_virt_start = DIRECTMAP_VIRT_START + > - (base_mfn - mfn) * PAGE_SIZE; > + (base_mfn - mfn_gb) * PAGE_SIZE; > } [...] > + rc = map_pages_to_xen((vaddr_t)__mfn_to_virt(base_mfn), > + _mfn(base_mfn), nr_mfns, > + PAGE_HYPERVISOR_RW | _PAGE_BLOCK); > + if ( rc ) > + panic("Unable to setup the xenheap mappings.\n"); I understand the intent of the code and I like it. maddr_to_virt is implemented as: return (void *)(XENHEAP_VIRT_START - (xenheap_base_pdx << PAGE_SHIFT) + ((ma & ma_va_bottom_mask) | ((ma & ma_top_mask) >> pfn_pdx_hole_shift))); The PDX stuff is always difficult to follow and I cannot claim that I traced through exactly what the resulting virtual address in the mapping would be for a given base_mfn, but the patch looks correct compared to the previous code. Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
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