Messages in this thread |  | | Date | Mon, 6 Apr 2020 08:24:11 -0700 | From | Christoph Hellwig <> | Subject | Re: [RFC PATCH] x86/split_lock: Disable SLD if an unaware (out-of-tree) module enables VMX |
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On Mon, Apr 06, 2020 at 04:04:03PM +0200, Peter Zijlstra wrote: > On Mon, Apr 06, 2020 at 05:50:10AM -0700, Christoph Hellwig wrote: > > On Fri, Apr 03, 2020 at 09:30:07AM -0700, Sean Christopherson wrote: > > > Hook into native CR4 writes to disable split-lock detection if CR4.VMXE > > > is toggled on by an SDL-unaware entity, e.g. an out-of-tree hypervisor > > > module. Most/all VMX-based hypervisors blindly reflect #AC exceptions > > > into the guest, or don't intercept #AC in the first place. With SLD > > > enabled, this results in unexpected #AC faults in the guest, leading to > > > crashes in the guest and other undesirable behavior. > > > > Out of tree modules do not matter, so we should not add code just to > > work around broken third party code. If you really feel strongly just > > make sure something they rely on for their hacks stops being exported > > and they are properly broken. > > Something like so then? > > I couldn't find any in-tree users for unmap_kernel_range*(),
zsmalloc.c can be built modular. Not that I think it should..
> and this > removes __get_vm_area() and with the ability to custom ranges. It also > removes map_vm_area() and replaces it with map_vm_area_nx() which kills > adding executable maps.
The pbh/electra change looks sensible. ipu3 as said really should use vmap, with that map_vm_area can also become unexported. In fact with a vmap variant that allos passing the type of memory for /proc/vmallocinfo we can just kill off map_vm_area enrirely and fold it into the two remaining callers.
I'll prepare proper series for the vmalloc area cleanups if you don't mind.
> > --- > diff --git a/arch/powerpc/include/asm/pasemi_dma.h b/arch/powerpc/include/asm/pasemi_dma.h > index 712a0b32120f..305c54d56244 100644 > --- a/arch/powerpc/include/asm/pasemi_dma.h > +++ b/arch/powerpc/include/asm/pasemi_dma.h > @@ -523,4 +523,6 @@ extern void pasemi_dma_free_fun(int fun); > /* Initialize the library, must be called before any other functions */ > extern int pasemi_dma_init(void); > > +extern struct vm_struct *get_phb_area(unsigned long size, unsigned long flags); > + > #endif /* ASM_PASEMI_DMA_H */ > diff --git a/arch/powerpc/platforms/pasemi/dma_lib.c b/arch/powerpc/platforms/pasemi/dma_lib.c > index 270fa3c0d372..0aae02df061d 100644 > --- a/arch/powerpc/platforms/pasemi/dma_lib.c > +++ b/arch/powerpc/platforms/pasemi/dma_lib.c > @@ -617,3 +617,10 @@ int pasemi_dma_init(void) > return err; > } > EXPORT_SYMBOL(pasemi_dma_init); > + > +struct vm_struct *get_phb_area(unsigned long size, unsigned long flags) > +{ > + return __get_vm_area_node(size, 1, flags, PHB_IO_BASE, PHB_IO_END, NUMA_NO_NODE, > + GFP_KERNEL, __builtin_return_address(0)); > +} > +EXPORT_SYMBOL_GPL(get_phb_area); > diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h > index 65c2ecd730c5..0bd5ea46f1d2 100644 > --- a/arch/x86/include/asm/pgtable_types.h > +++ b/arch/x86/include/asm/pgtable_types.h > @@ -274,6 +274,11 @@ typedef struct pgprot { pgprotval_t pgprot; } pgprot_t; > > typedef struct { pgdval_t pgd; } pgd_t; > > +static inline pgprot_t pgprot_nx(pgprot_t prot) > +{ > + return __pgprot(pgprot_val(prot) | _PAGE_NX); > +} > + > #ifdef CONFIG_X86_PAE > > /* > diff --git a/drivers/pcmcia/electra_cf.c b/drivers/pcmcia/electra_cf.c > index f2741c04289d..42eb242b29f1 100644 > --- a/drivers/pcmcia/electra_cf.c > +++ b/drivers/pcmcia/electra_cf.c > @@ -22,6 +22,8 @@ > #include <linux/of_platform.h> > #include <linux/slab.h> > > +#include <asm/pasemi_dma.h> > + > #include <pcmcia/ss.h> > > static const char driver_name[] = "electra-cf"; > @@ -204,7 +206,7 @@ static int electra_cf_probe(struct platform_device *ofdev) > cf->mem_base = ioremap(cf->mem_phys, cf->mem_size); > cf->io_size = PAGE_ALIGN(resource_size(&io)); > > - area = __get_vm_area(cf->io_size, 0, PHB_IO_BASE, PHB_IO_END); > + area = get_phb_area(cf->io_size, 0); > if (area == NULL) { > status = -ENOMEM; > goto fail1; > diff --git a/drivers/staging/media/ipu3/ipu3-dmamap.c b/drivers/staging/media/ipu3/ipu3-dmamap.c > index 7431322379f6..fc3fe85c340c 100644 > --- a/drivers/staging/media/ipu3/ipu3-dmamap.c > +++ b/drivers/staging/media/ipu3/ipu3-dmamap.c > @@ -124,13 +124,13 @@ void *imgu_dmamap_alloc(struct imgu_device *imgu, struct imgu_css_map *map, > } > > /* Now grab a virtual region */ > - map->vma = __get_vm_area(size, VM_USERMAP, VMALLOC_START, VMALLOC_END); > + map->vma = get_vm_area(size, VM_USERMAP); > if (!map->vma) > goto out_unmap; > > map->vma->pages = pages; > /* And map it in KVA */ > - if (map_vm_area(map->vma, PAGE_KERNEL, pages)) > + if (map_vm_area_nx(map->vma, PAGE_KERNEL, pages)) > goto out_vunmap; > > map->size = size; > diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h > index e2e2bef07dd2..ee66c1f8b141 100644 > --- a/include/asm-generic/pgtable.h > +++ b/include/asm-generic/pgtable.h > @@ -490,6 +490,10 @@ static inline int arch_unmap_one(struct mm_struct *mm, > #define flush_tlb_fix_spurious_fault(vma, address) flush_tlb_page(vma, address) > #endif > > +#ifndef pgprot_nx > +#define pgprot_nx(prot) (prot) > +#endif > + > #ifndef pgprot_noncached > #define pgprot_noncached(prot) (prot) > #endif > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 6b8eeb0ecee5..a1c5faa6042e 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2029,7 +2029,6 @@ void unmap_kernel_range_noflush(unsigned long addr, unsigned long size) > { > vunmap_page_range(addr, addr + size); > } > -EXPORT_SYMBOL_GPL(unmap_kernel_range_noflush); > > /** > * unmap_kernel_range - unmap kernel VM area and flush cache and TLB > @@ -2047,7 +2046,6 @@ void unmap_kernel_range(unsigned long addr, unsigned long size) > vunmap_page_range(addr, end); > flush_tlb_kernel_range(addr, end); > } > -EXPORT_SYMBOL_GPL(unmap_kernel_range); > > int map_vm_area(struct vm_struct *area, pgprot_t prot, struct page **pages) > { > @@ -2059,7 +2057,12 @@ int map_vm_area(struct vm_struct *area, pgprot_t prot, struct page **pages) > > return err > 0 ? 0 : err; > } > -EXPORT_SYMBOL_GPL(map_vm_area); > + > +int map_vm_area_nx(struct vm_struct *area, pgprot prot, struct page **pages) > +{ > + return map_vm_area(area, pgprot_nx(prot), pages); > +} > +EXPORT_SYMBOL_GPL(map_vm_area_nx); > > static inline void setup_vmalloc_vm_locked(struct vm_struct *vm, > struct vmap_area *va, unsigned long flags, const void *caller) > @@ -2133,7 +2136,6 @@ struct vm_struct *__get_vm_area(unsigned long size, unsigned long flags, > return __get_vm_area_node(size, 1, flags, start, end, NUMA_NO_NODE, > GFP_KERNEL, __builtin_return_address(0)); > } > -EXPORT_SYMBOL_GPL(__get_vm_area); > > struct vm_struct *__get_vm_area_caller(unsigned long size, unsigned long flags, > unsigned long start, unsigned long end, > @@ -2160,6 +2162,7 @@ struct vm_struct *get_vm_area(unsigned long size, unsigned long flags) > NUMA_NO_NODE, GFP_KERNEL, > __builtin_return_address(0)); > } > +EXPORT_SYMBOL_GPL(get_vm_area); > > struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags, > const void *caller) ---end quoted text---
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