Messages in this thread | | | Date | Tue, 12 Oct 2021 14:31:00 +0200 | Subject | Re: [PATCH v5 08/14] KVM: s390: pv: handle secure storage exceptions for normal guests | From | Janosch Frank <> |
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On 10/12/21 10:35, Claudio Imbrenda wrote: > On Tue, 12 Oct 2021 10:16:26 +0200 > Janosch Frank <frankja@linux.ibm.com> wrote: > >> On 9/20/21 15:24, Claudio Imbrenda wrote: >>> With upcoming patches, normal guests might touch secure pages. >>> >>> This patch extends the existing exception handler to convert the pages >>> to non secure also when the exception is triggered by a normal guest. >>> >>> This can happen for example when a secure guest reboots; the first >>> stage of a secure guest is non secure, and in general a secure guest >>> can reboot into non-secure mode. >>> >>> If the secure memory of the previous boot has not been cleared up >>> completely yet, a non-secure guest might touch secure memory, which >>> will need to be handled properly. >>> >>> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com> >>> --- >>> arch/s390/mm/fault.c | 10 +++++++++- >>> 1 file changed, 9 insertions(+), 1 deletion(-) >>> >>> diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c >>> index eb68b4f36927..74784581f42d 100644 >>> --- a/arch/s390/mm/fault.c >>> +++ b/arch/s390/mm/fault.c >>> @@ -767,6 +767,7 @@ void do_secure_storage_access(struct pt_regs *regs) >>> struct vm_area_struct *vma; >>> struct mm_struct *mm; >>> struct page *page; >>> + struct gmap *gmap; >>> int rc; >>> >>> /* >>> @@ -796,6 +797,14 @@ void do_secure_storage_access(struct pt_regs *regs) >>> } >>> >>> switch (get_fault_type(regs)) { >>> + case GMAP_FAULT: >>> + gmap = (struct gmap *)S390_lowcore.gmap; >>> + addr = __gmap_translate(gmap, addr); >>> + if (IS_ERR_VALUE(addr)) { >>> + do_fault_error(regs, VM_ACCESS_FLAGS, VM_FAULT_BADMAP); >>> + break; >>> + } >>> + fallthrough; >> >> This would trigger an export and not a destroy, right? > > correct. but this would only happen for leftover secure pages touched > by non-secure guests, before the background thread could clean them up.
I.e. we don't expect to need the destroy speed boost?
> >> >>> case USER_FAULT: >>> mm = current->mm; >>> mmap_read_lock(mm); >>> @@ -824,7 +833,6 @@ void do_secure_storage_access(struct pt_regs *regs) >>> if (rc) >>> BUG(); >>> break; >>> - case GMAP_FAULT: >>> default: >>> do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP); >>> WARN_ON_ONCE(1); >>> >> >
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