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

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Message-ID: <20250112095527.434998-5-pbonzini@redhat.com>
Date: Sun, 12 Jan 2025 10:55:26 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc: seanjc@...gle.com,
	linuxppc-dev@...ts.ozlabs.org,
	regressions@...ts.linux.dev,
	Christian Zigotzky <chzigotzky@...osoft.de>
Subject: [PATCH 4/5] KVM: e500: map readonly host pages for read

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@...hat.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