Author: kib Date: Mon Mar 26 16:31:12 2018 New Revision: 331557 URL: https://svnweb.freebsd.org/changeset/base/331557
Log: Allow to specify for vm_fault_quick_hold_pages() that nofault mode should be honored. We must not sleep or acquire any MI VM locks if TDP_NOFAULTING is specified. On the other hand, there were some callers in the tree which set TDP_NOFAULTING for larger scope than needed, I fixed the code which I wrote, but I suspect that linuxkpi and out of tree drm drivers might abuse this still. So only enable the mode for vm_fault_quick_hold_pages() where vm_fault_hold() is not called when specifically asked by user. I decided to use vm_prot_t flag to not change KPI. Since number of flags in vm_prot_t is limited, I reused the same flag which was already consumed for vm_map_lookup(). Reported and tested by: pho (as part of the larger patch) Reviewed by: markj Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D14825 Modified: head/sys/vm/vm.h head/sys/vm/vm_fault.c Modified: head/sys/vm/vm.h ============================================================================== --- head/sys/vm/vm.h Mon Mar 26 16:06:04 2018 (r331556) +++ head/sys/vm/vm.h Mon Mar 26 16:31:12 2018 (r331557) @@ -80,7 +80,9 @@ typedef u_char vm_prot_t; /* protection codes */ #define VM_PROT_WRITE ((vm_prot_t) 0x02) #define VM_PROT_EXECUTE ((vm_prot_t) 0x04) #define VM_PROT_COPY ((vm_prot_t) 0x08) /* copy-on-read */ -#define VM_PROT_FAULT_LOOKUP ((vm_prot_t) 0x010) +#define VM_PROT_PRIV_FLAG ((vm_prot_t) 0x10) +#define VM_PROT_FAULT_LOOKUP VM_PROT_PRIV_FLAG +#define VM_PROT_QUICK_NOFAULT VM_PROT_PRIV_FLAG /* same to save bits */ #define VM_PROT_ALL (VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE) #define VM_PROT_RW (VM_PROT_READ|VM_PROT_WRITE) Modified: head/sys/vm/vm_fault.c ============================================================================== --- head/sys/vm/vm_fault.c Mon Mar 26 16:06:04 2018 (r331556) +++ head/sys/vm/vm_fault.c Mon Mar 26 16:31:12 2018 (r331557) @@ -1524,7 +1524,18 @@ vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t ad * page was mapped at the specified virtual address or that * mapping had insufficient permissions. Attempt to fault in * and hold these pages. + * + * If vm_fault_disable_pagefaults() was called, + * i.e., TDP_NOFAULTING is set, we must not sleep nor + * acquire MD VM locks, which means we must not call + * vm_fault_hold(). Some (out of tree) callers mark + * too wide a code area with vm_fault_disable_pagefaults() + * already, use the VM_PROT_QUICK_NOFAULT flag to request + * the proper behaviour explicitly. */ + if ((prot & VM_PROT_QUICK_NOFAULT) != 0 && + (curthread->td_pflags & TDP_NOFAULTING) != 0) + goto error; for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) if (*mp == NULL && vm_fault_hold(map, va, prot, VM_FAULT_NORMAL, mp) != KERN_SUCCESS) _______________________________________________ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "[email protected]"
