[PATCH 4/5] KVM: e500: map readonly host pages for read

Paolo Bonzini
2025-01-12T09:55:46Z

The new __kvm_faultin_pfn() function is upset by the fact that e500 KVM
ignores host page permissions - __kvm_faultin requires a "writable"
outgoing argument, but e500 KVM is nonchalantly passing NULL.

If the host page permissions do not include writability, the shadow
TLB entry is forcibly mapped read-only.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/powerpc/kvm/e500_mmu_host.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
index b1be39639d4a..b38679e5821b 100644
--- a/arch/powerpc/kvm/e500_mmu_host.c
+++ b/arch/powerpc/kvm/e500_mmu_host.c
@@ -374,6 +374,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
unsigned long slot_start, slot_end;

pfnmap = 1;
+ writable = vma->vm_flags & VM_WRITE;

start = vma->vm_pgoff;
end = start +
@@ -449,7 +450,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,

if (likely(!pfnmap)) {
tsize_pages = 1UL << (tsize + 10 - PAGE_SHIFT);
- pfn = __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, NULL, &page);
+ pfn = __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, &writable, &page);
if (is_error_noslot_pfn(pfn)) {
if (printk_ratelimit())
pr_err("%s: real page not found for gfn %lx\n",
@@ -494,7 +495,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
}
local_irq_restore(flags);

- kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg, true);
+ kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg, writable);
kvmppc_e500_setup_stlbe(&vcpu_e500->vcpu, gtlbe, tsize,
ref, gvaddr, stlbe);
writable = tlbe_is_writable(stlbe);
--
2.47.1