linux-kernel - [PATCH 3.16 148/328] KVM: PPC: Book3S HV: Don't truncate HPTE index in xlate function

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Message-ID: <lsq.1544392233.349271258@decadent.org.uk>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Paul Mackerras" <paulus@...abs.org>
Subject: [PATCH 3.16 148/328] KVM: PPC: Book3S HV: Don't truncate HPTE
 index in xlate function

3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Paul Mackerras <paulus@...abs.org>

commit 46dec40fb741f00f1864580130779aeeaf24fb3d upstream.

This fixes a bug which causes guest virtual addresses to get translated
to guest real addresses incorrectly when the guest is using the HPT MMU
and has more than 256GB of RAM, or more specifically has a HPT larger
than 2GB.  This has showed up in testing as a failure of the host to
emulate doorbell instructions correctly on POWER9 for HPT guests with
more than 256GB of RAM.

The bug is that the HPTE index in kvmppc_mmu_book3s_64_hv_xlate()
is stored as an int, and in forming the HPTE address, the index gets
shifted left 4 bits as an int before being signed-extended to 64 bits.
The simple fix is to make the variable a long int, matching the
return type of kvmppc_hv_find_lock_hpte(), which is what calculates
the index.

Fixes: 697d3899dcb4 ("KVM: PPC: Implement MMIO emulation support for Book3S HV guests")
Signed-off-by: Paul Mackerras <paulus@...abs.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/powerpc/kvm/book3s_64_mmu_hv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -451,7 +451,7 @@ static int kvmppc_mmu_book3s_64_hv_xlate
 	unsigned long pp, key;
 	unsigned long v, gr;
 	unsigned long *hptep;
-	int index;
+	long int index;
 	int virtmode = vcpu->arch.shregs.msr & (data ? MSR_DR : MSR_IR);

 	/* Get SLB entry */