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Subject[PATCH 5.9 021/152] powerpc/64s/exception: KVM Fix for host DSI being taken in HPT guest MMU context
Date
From: Nicholas Piggin <npiggin@gmail.com>

commit cd81acc600a9684ea4b4d25a47900d38a3890eab upstream.

Commit 2284ffea8f0c ("powerpc/64s/exception: Only test KVM in SRR
interrupts when PR KVM is supported") removed KVM guest tests from
interrupts that do not set HV=1, when PR-KVM is not configured.

This is wrong for HV-KVM HPT guest MMIO emulation case which attempts
to load the faulting instruction word with MSR[DR]=1 and MSR[HV]=1 with
the guest MMU context loaded. This can cause host DSI, DSLB interrupts
which must test for KVM guest. Restore this and add a comment.

Fixes: 2284ffea8f0c ("powerpc/64s/exception: Only test KVM in SRR interrupts when PR KVM is supported")
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201117135617.3521127-1-npiggin@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/powerpc/kernel/exceptions-64s.S | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1410,6 +1410,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
* If none is found, do a Linux page fault. Linux page faults can happen in
* kernel mode due to user copy operations of course.
*
+ * KVM: The KVM HDSI handler may perform a load with MSR[DR]=1 in guest
+ * MMU context, which may cause a DSI in the host, which must go to the
+ * KVM handler. MSR[IR] is not enabled, so the real-mode handler will
+ * always be used regardless of AIL setting.
+ *
* - Radix MMU
* The hardware loads from the Linux page table directly, so a fault goes
* immediately to Linux page fault.
@@ -1420,10 +1425,8 @@ INT_DEFINE_BEGIN(data_access)
IVEC=0x300
IDAR=1
IDSISR=1
-#ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
IKVM_SKIP=1
IKVM_REAL=1
-#endif
INT_DEFINE_END(data_access)

EXC_REAL_BEGIN(data_access, 0x300, 0x80)
@@ -1462,6 +1465,8 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TY
* ppc64_bolted_size (first segment). The kernel handler must avoid stomping
* on user-handler data structures.
*
+ * KVM: Same as 0x300, DSLB must test for KVM guest.
+ *
* A dedicated save area EXSLB is used (XXX: but it actually need not be
* these days, we could use EXGEN).
*/
@@ -1470,10 +1475,8 @@ INT_DEFINE_BEGIN(data_access_slb)
IAREA=PACA_EXSLB
IRECONCILE=0
IDAR=1
-#ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
IKVM_SKIP=1
IKVM_REAL=1
-#endif
INT_DEFINE_END(data_access_slb)

EXC_REAL_BEGIN(data_access_slb, 0x380, 0x80)

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