linux-kernel - [PATCH 4.4 23/97] KVM: PPC: Book3S PR: Exit KVM on failed mapping

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Message-Id: <20180323094158.925063329@linuxfoundation.org>
Date:   Fri, 23 Mar 2018 10:54:10 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alexey Kardashevskiy <aik@...abs.ru>,
        David Gibson <david@...son.dropbear.id.au>,
        Paul Mackerras <paulus@...abs.org>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.4 23/97] KVM: PPC: Book3S PR: Exit KVM on failed mapping

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alexey Kardashevskiy <aik@...abs.ru>


[ Upstream commit bd9166ffe624000140fc6b606b256df01fc0d060 ]

At the moment kvmppc_mmu_map_page() returns -1 if
mmu_hash_ops.hpte_insert() fails for any reason so the page fault handler
resumes the guest and it faults on the same address again.

This adds distinction to kvmppc_mmu_map_page() to return -EIO if
mmu_hash_ops.hpte_insert() failed for a reason other than full pteg.
At the moment only pSeries_lpar_hpte_insert() returns -2 if
plpar_pte_enter() failed with a code other than H_PTEG_FULL.
Other mmu_hash_ops.hpte_insert() instances can only fail with
-1 "full pteg".

With this change, if PR KVM fails to update HPT, it can signal
the userspace about this instead of returning to guest and having
the very same page fault over and over again.

Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
Reviewed-by: David Gibson <david@...son.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@...abs.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/powerpc/kvm/book3s_64_mmu_host.c |    5 ++++-
 arch/powerpc/kvm/book3s_pr.c          |    6 +++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

--- a/arch/powerpc/kvm/book3s_64_mmu_host.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_host.c
@@ -177,12 +177,15 @@ map_again:
 	ret = ppc_md.hpte_insert(hpteg, vpn, hpaddr, rflags, vflags,
 				 hpsize, hpsize, MMU_SEGSIZE_256M);
 
-	if (ret < 0) {
+	if (ret == -1) {
 		/* If we couldn't map a primary PTE, try a secondary */
 		hash = ~hash;
 		vflags ^= HPTE_V_SECONDARY;
 		attempt++;
 		goto map_again;
+	} else if (ret < 0) {
+		r = -EIO;
+		goto out_unlock;
 	} else {
 		trace_kvm_book3s_64_mmu_map(rflags, hpteg,
 					    vpn, hpaddr, orig_pte);
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -625,7 +625,11 @@ int kvmppc_handle_pagefault(struct kvm_r
 			kvmppc_mmu_unmap_page(vcpu, &pte);
 		}
 		/* The guest's PTE is not mapped yet. Map on the host */
-		kvmppc_mmu_map_page(vcpu, &pte, iswrite);
+		if (kvmppc_mmu_map_page(vcpu, &pte, iswrite) == -EIO) {
+			/* Exit KVM if mapping failed */
+			run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+			return RESUME_HOST;
+		}
 		if (data)
 			vcpu->stat.sp_storage++;
 		else if (vcpu->arch.mmu.is_dcbz32(vcpu) &&