[Qemu-devel] [PATCH] target-arm: Fix reset and migration of TTBCR(S)

[Peter Maydell <peter.maydell@linaro.org>]

Commit 6459b94c26dd666badb3 broke reset and migration of the AArch32
TTBCR(S) register if the guest used non-LPAE page tables. This is
because the AArch32 TTBCR register definition is marked as ARM_CP_ALIAS,
meaning that the AArch64 variant has to handle migration and reset.
Although AArch64 TCR_EL3 doesn't need to care about the mask and
base_mask fields, AArch32 may do so, and so we must use the special
TTBCR reset and raw write functions to ensure they are set correctly.

This doesn't affect TCR_EL2, because the AArch32 equivalent of that
is HTCR, which never uses the non-LPAE page table variant.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reported-by: Pranith Kumar <bobby.prani+qemu@gmail.com>
---
 target-arm/helper.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/target-arm/helper.c b/target-arm/helper.c
index 862e780..c9730d6 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -3765,8 +3765,11 @@ static const ARMCPRegInfo el3_cp_reginfo[] = {
       .opc0 = 3, .opc1 = 6, .crn = 2, .crm = 0, .opc2 = 2,
       .access = PL3_RW,
       /* no .writefn needed as this can't cause an ASID change;
-       * no .raw_writefn or .resetfn needed as we never use mask/base_mask
+       * we must provide a .raw_writefn and .resetfn because we handle
+       * reset and migration for the AArch32 TTBCR(S), which might be
+       * using mask and base_mask.
        */
+      .resetfn = vmsa_ttbcr_reset, .raw_writefn = vmsa_ttbcr_raw_write,
       .fieldoffset = offsetof(CPUARMState, cp15.tcr_el[3]) },
     { .name = "ELR_EL3", .state = ARM_CP_STATE_AA64,
       .type = ARM_CP_ALIAS,
-- 
1.9.1