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Fix two PMP-related bugs: 

1. Generating PMP load/store exceptions when the instruction is not a load/store
2. Passing a PMP exec permission exception into M whilst the frontend is still
   starved, causing early taking of the exception and a bad mepc value.
This commit is contained in:
Luke Wren 2022-05-25 13:16:27 +01:00
parent 7340765699
commit e2b9a3b2f9
1 changed files with 8 additions and 2 deletions
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10
hdl/hazard3_core.v
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@ -730,6 +730,9 @@ wire x_exec_pmp_fail;
generate generate
if (PMP_REGIONS > 0) begin: have_pmp if (PMP_REGIONS > 0) begin: have_pmp
wire x_loadstore_pmp_badperm;
assign x_loadstore_pmp_fail = x_loadstore_pmp_badperm && x_memop_vld;
hazard3_pmp #( hazard3_pmp #(
`include "hazard3_config_inst.vh" `include "hazard3_config_inst.vh"
) pmp ( ) pmp (
@ -751,7 +754,7 @@ if (PMP_REGIONS > 0) begin: have_pmp
.d_addr (bus_haddr_d), .d_addr (bus_haddr_d),
.d_m_mode (x_mmode_loadstore), .d_m_mode (x_mmode_loadstore),
.d_write (bus_hwrite_d), .d_write (bus_hwrite_d),
.d_kill (x_loadstore_pmp_fail) .d_kill (x_loadstore_pmp_badperm)
); );
end else begin: no_pmp end else begin: no_pmp
@ -899,7 +902,10 @@ always @ (posedge clk or negedge rst_n) begin
xm_memop <= x_unaligned_addr ? MEMOP_NONE : d_memop; xm_memop <= x_unaligned_addr ? MEMOP_NONE : d_memop;
xm_except <= x_except; xm_except <= x_except;
xm_wfi <= d_wfi; xm_wfi <= d_wfi;
if (x_stall || m_trap_enter_soon) begin // Note the d_starved term is required because it is possible
// (e.g. PMP X permission fail) to except when the frontend is
// starved, and we get a bad mepc if we let this jump ahead:
if (x_stall || d_starved || m_trap_enter_soon) begin
// Insert bubble // Insert bubble
xm_rd <= {W_REGADDR{1'b0}}; xm_rd <= {W_REGADDR{1'b0}};
xm_memop <= MEMOP_NONE; xm_memop <= MEMOP_NONE;