On Tue, Mar 3, 2015 at 2:06 AM, David Vrabel <david.vrabel at citrix.com> wrote:> On 03/03/15 09:40, Luis R. Rodriguez wrote: >> Andrey, >> >> I believe that on Xen we should disable kasan, would like confirmation > > Why? This is the first of heard of this.Andrey chimed in here confirming this.>> from someone on xen-devel though. Here's the thing though -- if true >> -- I'd like to do it *properly*, where *properly* means addressing a >> bit of architecture. A simple Kconfig slap seems rather reactive. I'd >> like to address a way to properly ensure we don't run into this and >> other similar issues in the future. The CR4 shadow issue was another >> recent example issue, also introduced via v4.0 [0]. We can't keep >> doing this reactively. >> >> Let's go down the rabbit hole for a bit. HAVE_ARCH_KASAN will be >> selected on x86 when: >> >> if X86_64 && SPARSEMEM_VMEMMAP >> >> Now Xen should not have SPARSEMEM_VMEMMAP but PVOPs' goal is to enable > > Why? Again, this is the first I've heard of this as well. FWIW, all > the Xen configs we use have SPARSEMEM_VMEMMAP enabled.Interesting... we have config ARCH_SPARSEMEM_ENABLE depend on !XEN at SUSE. Figured this was a generic issue. The SUSE kernels are based on 3.12 though, but anyway with it enabled I do get compile failures because of redefinition of MAX_PHYSMEM_BITS which we provide on Xen set to 43 for some reason (can't find that justification), so it doesn't use the default 46 that would be used otherwise. But another reason seems to be the lack of forward porting yet PAT support for PV domains -- commit 47591df50 upstream which requires us to still have the union on the pte_t, and I suppose we need ca15f20f as well... If there is nothing else I suppose this just requires fixing up at SUSE's end for SPARSEMEM_VMEMMAP... --- ./arch/x86/include/asm/pgtable_64_types.h 2015-03-02 13:35:49.885257763 -0800 +++ ./arch/x86/include/mach-xen/asm/pgtable_64_types.h 2015-03-02 13:36:25.554259348 -0800 @@ -15,7 +15,7 @@ typedef unsigned long pgdval_t; typedef unsigned long pgprotval_t; -typedef struct { pteval_t pte; } pte_t; +typedef union { pteval_t pte; unsigned int pte_low; } pte_t; #endif /* !__ASSEMBLY__ */ @@ -54,6 +54,7 @@ #define PGDIR_MASK (~(PGDIR_SIZE - 1)) /* See Documentation/x86/x86_64/mm.txt for a description of the memory map. */ +#define MAX_PHYSMEM_BITS 43 #define MAXMEM _AC(__AC(1, UL) << MAX_PHYSMEM_BITS, UL) #define VMALLOC_START _AC(0xffffc90000000000, UL) #define VMALLOC_END _AC(0xffffe8ffffffffff, UL) Luis
On 03/03/2015 08:20 PM, Luis R. Rodriguez wrote:> On Tue, Mar 3, 2015 at 2:06 AM, David Vrabel <david.vrabel at citrix.com> wrote: >> On 03/03/15 09:40, Luis R. Rodriguez wrote: >>> Andrey, >>> >>> I believe that on Xen we should disable kasan, would like confirmation >> >> Why? This is the first of heard of this. > > Andrey chimed in here confirming this. > >>> from someone on xen-devel though. Here's the thing though -- if true >>> -- I'd like to do it *properly*, where *properly* means addressing a >>> bit of architecture. A simple Kconfig slap seems rather reactive. I'd >>> like to address a way to properly ensure we don't run into this and >>> other similar issues in the future. The CR4 shadow issue was another >>> recent example issue, also introduced via v4.0 [0]. We can't keep >>> doing this reactively. >>> >>> Let's go down the rabbit hole for a bit. HAVE_ARCH_KASAN will be >>> selected on x86 when: >>> >>> if X86_64 && SPARSEMEM_VMEMMAP >>> >>> Now Xen should not have SPARSEMEM_VMEMMAP but PVOPs' goal is to enable >> >> Why? Again, this is the first I've heard of this as well. FWIW, all >> the Xen configs we use have SPARSEMEM_VMEMMAP enabled. > > Interesting... we have config ARCH_SPARSEMEM_ENABLE depend on !XEN at > SUSE. Figured this was a generic issue. The SUSE kernels are based on > 3.12 though, but anyway with it enabled I do get compile failures > because of redefinition of MAX_PHYSMEM_BITS which we provide on Xen > set to 43 for some reason (can't find that justification), so it > doesn't use the default 46 that would be used otherwise. But another > reason seems to be the lack of forward porting yet PAT support for PV > domains -- commit 47591df50 upstream which requires us to still have > the union on the pte_t, and I suppose we need ca15f20f as well... > > If there is nothing else I suppose this just requires fixing up at > SUSE's end for SPARSEMEM_VMEMMAP...The SUSE kernel has several patches renaming/altering Xen-related config options. Don't mix that up with upstream/pvops. Juergen
>>> On 04.03.15 at 05:53, <JGross at suse.com> wrote: > On 03/03/2015 08:20 PM, Luis R. Rodriguez wrote: >> On Tue, Mar 3, 2015 at 2:06 AM, David Vrabel <david.vrabel at citrix.com> wrote: >>> On 03/03/15 09:40, Luis R. Rodriguez wrote: >>>> if X86_64 && SPARSEMEM_VMEMMAP >>>> >>>> Now Xen should not have SPARSEMEM_VMEMMAP but PVOPs' goal is to enable >>> >>> Why? Again, this is the first I've heard of this as well. FWIW, all >>> the Xen configs we use have SPARSEMEM_VMEMMAP enabled. >> >> Interesting... we have config ARCH_SPARSEMEM_ENABLE depend on !XEN at >> SUSE. Figured this was a generic issue. The SUSE kernels are based on >> 3.12 though, but anyway with it enabled I do get compile failures >> because of redefinition of MAX_PHYSMEM_BITS which we provide on Xen >> set to 43 for some reason (can't find that justification), so it >> doesn't use the default 46 that would be used otherwise. But another >> reason seems to be the lack of forward porting yet PAT support for PV >> domains -- commit 47591df50 upstream which requires us to still have >> the union on the pte_t, and I suppose we need ca15f20f as well... >> >> If there is nothing else I suppose this just requires fixing up at >> SUSE's end for SPARSEMEM_VMEMMAP... > > The SUSE kernel has several patches renaming/altering Xen-related config > options. Don't mix that up with upstream/pvops.Exactly - some of what our kernels do in this regard could be useful upstream, while others (like this one) won't be. Prior to making claims against upstream kernels you should tell between these cases. Jan