KVM: PPC: Book3S PR: Preserve storage control bits

PR KVM page fault handler performs eaddr to pte translation for a guest,
however kvmppc_mmu_book3s_64_xlate() does not preserve WIMG bits
(storage control) in the kvmppc_pte struct. If PR KVM is running as
a second level guest under HV KVM, and PR KVM tries inserting HPT entry,
this fails in HV KVM if it already has this mapping.

This preserves WIMG bits between kvmppc_mmu_book3s_64_xlate() and
kvmppc_mmu_map_page().
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/include/asm/kvm_host.h

@@ -342,6 +342,7 @@ struct kvmppc_pte {
 	bool may_read		: 1;
 	bool may_write		: 1;
 	bool may_execute	: 1;
+	unsigned long wimg;
 	u8 page_size;		/* MMU_PAGE_xxx */
 };
 

arch/powerpc/kvm/book3s_64_mmu.c

@@ -319,6 +319,7 @@ static int kvmppc_mmu_book3s_64_xlate(struct kvm_vcpu *vcpu, gva_t eaddr,
 		gpte->may_execute = true;
 	gpte->may_read = false;
 	gpte->may_write = false;
+	gpte->wimg = r & HPTE_R_WIMG;
 
 	switch (pp) {
 	case 0:

arch/powerpc/kvm/book3s_64_mmu_host.c

@@ -145,6 +145,8 @@ int kvmppc_mmu_map_page(struct kvm_vcpu *vcpu, struct kvmppc_pte *orig_pte,
 	else
 		kvmppc_mmu_flush_icache(pfn);
 
+	rflags = (rflags & ~HPTE_R_WIMG) | orig_pte->wimg;
+
 	/*
 	 * Use 64K pages if possible; otherwise, on 64K page kernels,
 	 * we need to transfer 4 more bits from guest real to host real addr.

arch/powerpc/kvm/book3s_pr.c

@@ -537,7 +537,7 @@ int kvmppc_handle_pagefault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	int r = RESUME_GUEST;
 	int relocated;
 	int page_found = 0;
-	struct kvmppc_pte pte;
+	struct kvmppc_pte pte = { 0 };
 	bool dr = (kvmppc_get_msr(vcpu) & MSR_DR) ? true : false;
 	bool ir = (kvmppc_get_msr(vcpu) & MSR_IR) ? true : false;
 	u64 vsid;