KVM: PPC: Use kvm_vcpu_map() to map guest memory to patch dcbz instructions

Use kvm_vcpu_map() when patching dcbz in guest memory, as a regular GUP
isn't technically sufficient when writing to data in the target pages.
As per Documentation/core-api/pin_user_pages.rst:

      Correct (uses FOLL_PIN calls):
          pin_user_pages()
          write to the data within the pages
          unpin_user_pages()

      INCORRECT (uses FOLL_GET calls):
          get_user_pages()
          write to the data within the pages
          put_page()

As a happy bonus, using kvm_vcpu_{,un}map() takes care of creating a
mapping and marking the page dirty.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-75-seanjc@google.com>

diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index cd7ab6d85090918fdffad8e4f06d55b35a7e23f2..83bcdc80ce51ad1f23453bcc502ea6f816082abe 100644 (file)
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -639,28 +639,27 @@ static void kvmppc_set_pvr_pr(struct kvm_vcpu *vcpu, u32 pvr)
  */
 static void kvmppc_patch_dcbz(struct kvm_vcpu *vcpu, struct kvmppc_pte *pte)
 {
-       struct page *hpage;
+       struct kvm_host_map map;
        u64 hpage_offset;
        u32 *page;
-       int i;
+       int i, r;
 
-       hpage = gfn_to_page(vcpu->kvm, pte->raddr >> PAGE_SHIFT);
-       if (!hpage)
+       r = kvm_vcpu_map(vcpu, pte->raddr >> PAGE_SHIFT, &map);
+       if (r)
                return;
 
        hpage_offset = pte->raddr & ~PAGE_MASK;
        hpage_offset &= ~0xFFFULL;
        hpage_offset /= 4;
 
-       page = kmap_atomic(hpage);
+       page = map.hva;
 
        /* patch dcbz into reserved instruction, so we trap */
        for (i=hpage_offset; i < hpage_offset + (HW_PAGE_SIZE / 4); i++)
                if ((be32_to_cpu(page[i]) & 0xff0007ff) == INS_DCBZ)
                        page[i] &= cpu_to_be32(0xfffffff7);
 
-       kunmap_atomic(page);
-       put_page(hpage);
+       kvm_vcpu_unmap(vcpu, &map);
 }
 
 static bool kvmppc_visible_gpa(struct kvm_vcpu *vcpu, gpa_t gpa)