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authorPaul Mackerras <paulus@ozlabs.org>2018-02-24 10:08:51 +0100
committerPaul Mackerras <paulus@ozlabs.org>2018-03-19 00:08:44 +0100
commitf7caf712d885713986baeac86b1b64bcbd9dcd91 (patch)
tree7673855e408cd3309c1204634e5eea8a9a4646fd /arch/powerpc
parentKVM: PPC: Book3S HV: Radix page fault handler optimizations (diff)
downloadlinux-f7caf712d885713986baeac86b1b64bcbd9dcd91.tar.xz
linux-f7caf712d885713986baeac86b1b64bcbd9dcd91.zip
KVM: PPC: Book3S HV: Streamline setting of reference and change bits
When using the radix MMU, we can get hypervisor page fault interrupts with the DSISR_SET_RC bit set in DSISR/HSRR1, indicating that an attempt to set the R (reference) or C (change) bit in a PTE atomically failed. Previously we would find the corresponding Linux PTE and check the permission and dirty bits there, but this is not really necessary since we only need to do what the hardware was trying to do, namely set R or C atomically. This removes the code that reads the Linux PTE and just update the partition-scoped PTE, having first checked that it is still present, and if the access is a write, that the PTE still has write permission. Furthermore, we now check whether any other relevant bits are set in DSISR, and if there are, then we proceed with the rest of the function in order to handle whatever condition they represent, instead of returning to the guest as we did previously. Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/kvm/book3s_64_mmu_radix.c52
1 files changed, 19 insertions, 33 deletions
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index ed62164f8474..f783b067e5ac 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -345,7 +345,7 @@ int kvmppc_book3s_radix_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
unsigned long gpa, gfn, hva, pfn;
struct kvm_memory_slot *memslot;
struct page *page = NULL, *pages[1];
- long ret, npages, ok;
+ long ret, npages;
unsigned int writing;
struct vm_area_struct *vma;
unsigned long flags;
@@ -397,43 +397,29 @@ int kvmppc_book3s_radix_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
if (dsisr & DSISR_SET_RC) {
/*
* Need to set an R or C bit in the 2nd-level tables;
- * if the relevant bits aren't already set in the linux
- * page tables, fall through to do the gup_fast to
- * set them in the linux page tables too.
+ * since we are just helping out the hardware here,
+ * it is sufficient to do what the hardware does.
*/
- ok = 0;
pgflags = _PAGE_ACCESSED;
if (writing)
pgflags |= _PAGE_DIRTY;
- local_irq_save(flags);
- ptep = find_current_mm_pte(current->mm->pgd, hva, NULL, NULL);
- if (ptep) {
- pte = READ_ONCE(*ptep);
- if (pte_present(pte) &&
- (pte_val(pte) & pgflags) == pgflags)
- ok = 1;
- }
- local_irq_restore(flags);
- if (ok) {
- spin_lock(&kvm->mmu_lock);
- if (mmu_notifier_retry(vcpu->kvm, mmu_seq)) {
- spin_unlock(&kvm->mmu_lock);
- return RESUME_GUEST;
- }
- /*
- * We are walking the secondary page table here. We can do this
- * without disabling irq.
- */
- ptep = __find_linux_pte(kvm->arch.pgtable,
- gpa, NULL, &shift);
- if (ptep && pte_present(*ptep)) {
- kvmppc_radix_update_pte(kvm, ptep, 0, pgflags,
- gpa, shift);
- spin_unlock(&kvm->mmu_lock);
- return RESUME_GUEST;
- }
- spin_unlock(&kvm->mmu_lock);
+ /*
+ * We are walking the secondary page table here. We can do this
+ * without disabling irq.
+ */
+ spin_lock(&kvm->mmu_lock);
+ ptep = __find_linux_pte(kvm->arch.pgtable,
+ gpa, NULL, &shift);
+ if (ptep && pte_present(*ptep) &&
+ (!writing || pte_write(*ptep))) {
+ kvmppc_radix_update_pte(kvm, ptep, 0, pgflags,
+ gpa, shift);
+ dsisr &= ~DSISR_SET_RC;
}
+ spin_unlock(&kvm->mmu_lock);
+ if (!(dsisr & (DSISR_BAD_FAULT_64S | DSISR_NOHPTE |
+ DSISR_PROTFAULT | DSISR_SET_RC)))
+ return RESUME_GUEST;
}
ret = -EFAULT;