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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2016-03-08 12:12:18 +0100
committerChristian Borntraeger <borntraeger@de.ibm.com>2016-06-20 09:54:04 +0200
commit4be130a08420d6918d80c1067f8078f425eb98df (patch)
treec3e323bf6597eea8e588586550e378acf7652ce2 /arch/s390/mm/fault.c
parent6ea427bbbd4078297bb1dbd6c5cb83f3f48aac46 (diff)
downloadlinux-4be130a08420d6918d80c1067f8078f425eb98df.tar.bz2
s390/mm: add shadow gmap support
For a nested KVM guest the outer KVM host needs to create shadow page tables for the nested guest. This patch adds the basic support to the guest address space (gmap) code. For each guest address space the inner KVM host creates, the first outer KVM host needs to create shadow page tables. The address space is identified by the ASCE loaded into the control register 1 at the time the inner SIE instruction for the second nested KVM guest is executed. The outer KVM host creates the shadow tables starting with the table identified by the ASCE on a on-demand basis. The outer KVM host will get repeated faults for all the shadow tables needed to run the second KVM guest. While a shadow page table for the second KVM guest is active the access to the origin region, segment and page tables needs to be restricted for the first KVM guest. For region and segment and page tables the first KVM guest may read the memory, but write attempt has to lead to an unshadow. This is done using the page invalid and read-only bits in the page table of the first KVM guest. If the first guest re-accesses one of the origin pages of a shadow, it gets a fault and the affected parts of the shadow page table hierarchy needs to be removed again. PGSTE tables don't have to be shadowed, as all interpretation assist can't deal with the invalid bits in the shadow pte being set differently than the original ones provided by the first KVM guest. Many bug fixes and improvements by David Hildenbrand. Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Diffstat (limited to 'arch/s390/mm/fault.c')
-rw-r--r--arch/s390/mm/fault.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 19288c1b36d3..b84416c11c43 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -418,6 +418,7 @@ static inline int do_exception(struct pt_regs *regs, int access)
(struct gmap *) S390_lowcore.gmap : NULL;
if (gmap) {
current->thread.gmap_addr = address;
+ current->thread.gmap_write_flag = !!(flags & FAULT_FLAG_WRITE);
address = __gmap_translate(gmap, address);
if (address == -EFAULT) {
fault = VM_FAULT_BADMAP;