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HPTW cleanup

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This commit is contained in:
David Harris 2022-11-04 15:21:09 -07:00
parent 23268d22e5
commit e57083a0ef
4 changed files with 110 additions and 92 deletions
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118
pipelined/src/mmu/hptw.sv
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@ -42,7 +42,7 @@ module hptw
input logic [1:0] STATUS_MPP,
input logic [1:0] PrivilegeModeW,
(* mark_debug = "true" *) input logic ITLBMissOrDAFaultNoTrapF, DTLBMissOrDAFaultNoTrapM, // TLB Miss
input logic [`XLEN-1:0] HPTWReadPTE, // page table entry from LSU
input logic [`XLEN-1:0] HPTWReadPTE, // page table entry from LSU *** change to ReadDataM
input logic DCacheStallM, // stall from LSU
output logic [`XLEN-1:0] PTE, // page table entry to TLBs
output logic [1:0] PageType, // page type to TLBs
@ -106,7 +106,6 @@ module hptw
if(`HPTW_WRITES_SUPPORTED) begin : hptwwrites
logic SV39Mode;
logic ReadAccess, WriteAccess;
logic InvalidRead, InvalidWrite;
logic UpperBitsUnequalPageFault;
@ -136,19 +135,9 @@ module hptw
assign ImproperPrivilege = ((EffectivePrivilegeMode == `U_MODE) & ~PTE_U) |
((EffectivePrivilegeMode == `S_MODE) & PTE_U & (~STATUS_SUM & DTLBWalk));
// *** turn into module common with code in tlbcontrol.
if (`XLEN==64) begin:rv64
assign SV39Mode = (SATP_REGW[`XLEN-1:`XLEN-`SVMODE_BITS] == `SV39);
// page fault if upper bits aren't all the same
logic UpperEqual39, UpperEqual48;
assign UpperEqual39 = &(TranslationVAdr[63:38]) | ~|(TranslationVAdr[63:38]);
assign UpperEqual48 = &(TranslationVAdr[63:47]) | ~|(TranslationVAdr[63:47]);
assign UpperBitsUnequalPageFault = SV39Mode ? ~UpperEqual39 : ~UpperEqual48;
end else begin
assign SV39Mode = 0;
assign UpperBitsUnequalPageFault = 0;
end
// Check for page faults
vm64check vm64check(.SATP_MODE(SATP_REGW[`XLEN-1:`XLEN-`SVMODE_BITS]), .VAdr(TranslationVAdr),
.SV39Mode(), .UpperBitsUnequalPageFault);
assign InvalidRead = ReadAccess & ~Readable & (~STATUS_MXR | ~Executable);
assign InvalidWrite = WriteAccess & ~Writable;
assign OtherPageFault = DTLBWalk? ImproperPrivilege | InvalidRead | InvalidWrite | UpperBitsUnequalPageFault | Misaligned | ~Valid :
@ -190,26 +179,26 @@ module hptw
// HPTWAdr muxing
if (`XLEN==32) begin // RV32
logic [9:0] VPN;
logic [`PPN_BITS-1:0] PPN;
assign VPN = ((WalkerState == L1_ADR) | (WalkerState == L1_RD)) ? TranslationVAdr[31:22] : TranslationVAdr[21:12]; // select VPN field based on HPTW state
assign PPN = ((WalkerState == L1_ADR) | (WalkerState == L1_RD)) ? BasePageTablePPN : CurrentPPN;
assign HPTWReadAdr = {PPN, VPN, 2'b00};
assign HPTWSize = 3'b010;
logic [9:0] VPN;
logic [`PPN_BITS-1:0] PPN;
assign VPN = ((WalkerState == L1_ADR) | (WalkerState == L1_RD)) ? TranslationVAdr[31:22] : TranslationVAdr[21:12]; // select VPN field based on HPTW state
assign PPN = ((WalkerState == L1_ADR) | (WalkerState == L1_RD)) ? BasePageTablePPN : CurrentPPN;
assign HPTWReadAdr = {PPN, VPN, 2'b00};
assign HPTWSize = 3'b010;
end else begin // RV64
logic [8:0] VPN;
logic [`PPN_BITS-1:0] PPN;
always_comb
case (WalkerState) // select VPN field based on HPTW state
L3_ADR, L3_RD: VPN = TranslationVAdr[47:39];
L2_ADR, L2_RD: VPN = TranslationVAdr[38:30];
L1_ADR, L1_RD: VPN = TranslationVAdr[29:21];
default: VPN = TranslationVAdr[20:12];
endcase
assign PPN = ((WalkerState == L3_ADR) | (WalkerState == L3_RD) |
(SvMode != `SV48 & ((WalkerState == L2_ADR) | (WalkerState == L2_RD)))) ? BasePageTablePPN : CurrentPPN;
assign HPTWReadAdr = {PPN, VPN, 3'b000};
assign HPTWSize = 3'b011;
logic [8:0] VPN;
logic [`PPN_BITS-1:0] PPN;
always_comb
case (WalkerState) // select VPN field based on HPTW state
L3_ADR, L3_RD: VPN = TranslationVAdr[47:39];
L2_ADR, L2_RD: VPN = TranslationVAdr[38:30];
L1_ADR, L1_RD: VPN = TranslationVAdr[29:21];
default: VPN = TranslationVAdr[20:12];
endcase
assign PPN = ((WalkerState == L3_ADR) | (WalkerState == L3_RD) |
(SvMode != `SV48 & ((WalkerState == L2_ADR) | (WalkerState == L2_RD)))) ? BasePageTablePPN : CurrentPPN;
assign HPTWReadAdr = {PPN, VPN, 3'b000};
assign HPTWSize = 3'b011;
end
// Initial state and misalignment for RV32/64
@ -228,44 +217,33 @@ module hptw
end
// Page Table Walker FSM
// If the setup time on the D$ RAM is short, it should be possible to merge the LEVELx_READ and LEVELx states
// to decrease the latency of the HPTW. However, if the D$ is a cycle limiter, it's better to leave the
// HPTW as shown below to keep the D$ setup time out of the critical path.
// *** Is this really true. Talk with Ross. Seems like it's the next state logic on critical path instead.
// *** address TYPE(statetype)
flopenl #(.TYPE(statetype)) WalkerStateReg(clk, reset, 1'b1, NextWalkerState, IDLE, WalkerState);
always_comb
case (WalkerState)
IDLE: if (TLBMiss) NextWalkerState = InitialWalkerState;
else NextWalkerState = IDLE;
L3_ADR: NextWalkerState = L3_RD; // first access in SV48
L3_RD: if (DCacheStallM) NextWalkerState = L3_RD;
else NextWalkerState = L2_ADR;
L2_ADR: if (InitialWalkerState == L2_ADR) NextWalkerState = L2_RD; // first access in SV39
else if (ValidLeafPTE & ~Misaligned) NextWalkerState = LEAF; // could shortcut this by a cyle for all Lx_ADR superpages
else if (ValidNonLeafPTE) NextWalkerState = L2_RD;
else NextWalkerState = LEAF;
L2_RD: if (DCacheStallM) NextWalkerState = L2_RD;
else NextWalkerState = L1_ADR;
L1_ADR: if (InitialWalkerState == L1_ADR) NextWalkerState = L1_RD; // first access in SV32
else if (ValidLeafPTE & ~Misaligned) NextWalkerState = LEAF; // could shortcut this by a cyle for all Lx_ADR superpages
else if (ValidNonLeafPTE) NextWalkerState = L1_RD;
else NextWalkerState = LEAF;
L1_RD: if (DCacheStallM) NextWalkerState = L1_RD;
else NextWalkerState = L0_ADR;
L0_ADR: if (ValidLeafPTE & ~Misaligned) NextWalkerState = LEAF; // could shortcut this by a cyle for all Lx_ADR superpages
else if (ValidNonLeafPTE) NextWalkerState = L0_RD;
else NextWalkerState = LEAF;
L0_RD: if (DCacheStallM) NextWalkerState = L0_RD;
else NextWalkerState = LEAF;
LEAF: if (DAPageFault) NextWalkerState = UPDATE_PTE;
else NextWalkerState = IDLE;
UPDATE_PTE: if(`HPTW_WRITES_SUPPORTED & DCacheStallM) NextWalkerState = UPDATE_PTE;
else NextWalkerState = LEAF;
default: begin
NextWalkerState = IDLE; // should never be reached
end
endcase // case (WalkerState)
case (WalkerState)
IDLE: if (TLBMiss) NextWalkerState = InitialWalkerState;
else NextWalkerState = IDLE;
L3_ADR: NextWalkerState = L3_RD; // first access in SV48
L3_RD: if (DCacheStallM) NextWalkerState = L3_RD;
else NextWalkerState = L2_ADR;
L2_ADR: if (InitialWalkerState == L2_ADR | ValidNonLeafPTE) NextWalkerState = L2_RD; // first access in SV39
else NextWalkerState = LEAF;
L2_RD: if (DCacheStallM) NextWalkerState = L2_RD;
else NextWalkerState = L1_ADR;
L1_ADR: if (InitialWalkerState == L1_ADR | ValidNonLeafPTE) NextWalkerState = L1_RD; // first access in SV32
else if (ValidNonLeafPTE) NextWalkerState = L1_RD;
else NextWalkerState = LEAF;
L1_RD: if (DCacheStallM) NextWalkerState = L1_RD;
else NextWalkerState = L0_ADR;
L0_ADR: if (ValidNonLeafPTE) NextWalkerState = L0_RD;
else NextWalkerState = LEAF;
L0_RD: if (DCacheStallM) NextWalkerState = L0_RD;
else NextWalkerState = LEAF;
LEAF: if (DAPageFault) NextWalkerState = UPDATE_PTE;
else NextWalkerState = IDLE;
UPDATE_PTE: if(`HPTW_WRITES_SUPPORTED & DCacheStallM) NextWalkerState = UPDATE_PTE;
else NextWalkerState = LEAF;
default: NextWalkerState = IDLE; // should never be reached
endcase // case (WalkerState)
assign IgnoreRequestTLB = WalkerState == IDLE & TLBMiss;
assign SelHPTW = WalkerState != IDLE;

20
pipelined/src/mmu/tlb.sv
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@ -116,16 +116,16 @@ module tlb #(parameter TLB_ENTRIES = 8,
// we cache Misaligned along with the PTE? This only has to be computed once
// in the hptw as it is always the same regardless of the VPN.
if(`XLEN == 32) begin
assign MegapageMisaligned = |(PPN[9:0]); // must have zero PPN0
assign Misaligned = (HitPageType == 2'b01) & MegapageMisaligned;
assign MegapageMisaligned = |(PPN[9:0]); // must have zero PPN0
assign Misaligned = (HitPageType == 2'b01) & MegapageMisaligned;
end else begin
logic GigapageMisaligned, TerapageMisaligned;
assign TerapageMisaligned = |(PPN[26:0]); // must have zero PPN2, PPN1, PPN0
assign GigapageMisaligned = |(PPN[17:0]); // must have zero PPN1 and PPN0
assign MegapageMisaligned = |(PPN[8:0]); // must have zero PPN0
assign Misaligned = ((HitPageType == 2'b11) & TerapageMisaligned) |
((HitPageType == 2'b10) & GigapageMisaligned) |
((HitPageType == 2'b01) & MegapageMisaligned);
logic GigapageMisaligned, TerapageMisaligned;
assign TerapageMisaligned = |(PPN[26:0]); // must have zero PPN2, PPN1, PPN0
assign GigapageMisaligned = |(PPN[17:0]); // must have zero PPN1 and PPN0
assign MegapageMisaligned = |(PPN[8:0]); // must have zero PPN0
assign Misaligned = ((HitPageType == 2'b11) & TerapageMisaligned) |
((HitPageType == 2'b10) & GigapageMisaligned) |
((HitPageType == 2'b01) & MegapageMisaligned);
end
assign VPN = VAdr[`VPN_BITS+11:12];
@ -137,7 +137,7 @@ module tlb #(parameter TLB_ENTRIES = 8,
tlblru #(TLB_ENTRIES) lru(.clk, .reset, .TLBWrite, .TLBFlush, .Matches, .CAMHit, .WriteEnables);
tlbcam #(TLB_ENTRIES, `VPN_BITS + `ASID_BITS, `VPN_SEGMENT_BITS)
tlbcam(.clk, .reset, .VPN, .PageTypeWriteVal, .SV39Mode, .TLBFlush, .WriteEnables, .PTE_Gs,
tlbcam(.clk, .reset, .VPN, .PageTypeWriteVal, .SV39Mode, .TLBFlush, .WriteEnables, .PTE_Gs,
.SATP_ASID, .Matches, .HitPageType, .CAMHit);
tlbram #(TLB_ENTRIES) tlbram(.clk, .reset, .PTE, .Matches, .WriteEnables, .PPN, .PTEAccessBits, .PTE_Gs);

14
pipelined/src/mmu/tlbcontrol.sv
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@ -68,22 +68,12 @@ module tlbcontrol #(parameter ITLB = 0) (
// Grab the sv mode from SATP and determine whether translation should occur
assign EffectivePrivilegeMode = (ITLB == 1) ? PrivilegeModeW : (STATUS_MPRV ? STATUS_MPP : PrivilegeModeW); // DTLB uses MPP mode when MPRV is 1
assign Translate = (SATP_MODE != `NO_TRANSLATE) & (EffectivePrivilegeMode != `M_MODE) & ~DisableTranslation;
if (`XLEN==64) begin:rv64
assign SV39Mode = (SATP_MODE == `SV39);
// page fault if upper bits aren't all the same
logic UpperEqual39, UpperEqual48;
assign UpperEqual39 = &(VAdr[63:38]) | ~|(VAdr[63:38]);
assign UpperEqual48 = &(VAdr[63:47]) | ~|(VAdr[63:47]);
assign UpperBitsUnequalPageFault = SV39Mode ? ~UpperEqual39 : ~UpperEqual48;
end else begin
assign SV39Mode = 0;
assign UpperBitsUnequalPageFault = 0;
end
// Determine whether TLB is being used
assign TLBAccess = ReadAccess | WriteAccess;
// Check whether upper bits of virtual addresss are all equal
vm64check vm64check(.SATP_MODE, .VAdr, .SV39Mode, .UpperBitsUnequalPageFault);
// unswizzle useful PTE bits
assign {PTE_D, PTE_A} = PTEAccessBits[7:6];
@ -99,7 +89,7 @@ module tlbcontrol #(parameter ITLB = 0) (
assign DAPageFault = Translate & TLBHit & ~PTE_A & ~TLBPageFault;
assign TLBPageFault = (Translate & TLBHit & (ImproperPrivilege | ~PTE_X | UpperBitsUnequalPageFault | Misaligned | ~PTE_V));
end else begin
// fault for software handling if access bit is off
// fault for software handling if access bit is off
assign DAPageFault = ~PTE_A;
assign TLBPageFault = (Translate & TLBHit & (ImproperPrivilege | ~PTE_X | DAPageFault | UpperBitsUnequalPageFault | Misaligned | ~PTE_V));
end

50
pipelined/src/mmu/vm64check.sv Normal file
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@ -0,0 +1,50 @@
///////////////////////////////////////////
// vm64check.sv
//
// Written: David_Harris@hmc.edu 4 November 2022
// Modified:
//
// Purpose: Check for good upper address bits in RV64 mode
//
// A component of the Wally configurable RISC-V project.
//
// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
//
// MIT LICENSE
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
// OR OTHER DEALINGS IN THE SOFTWARE.
////////////////////////////////////////////////////////////////////////////////////////////////
`include "wally-config.vh"
module vm64check (
input logic [`SVMODE_BITS-1:0] SATP_MODE,
input logic [`XLEN-1:0] VAdr,
output logic SV39Mode, UpperBitsUnequalPageFault
);
if (`XLEN==64) begin:rv64
assign SV39Mode = (SATP_MODE == `SV39);
// page fault if upper bits aren't all the same
logic UpperEqual39, UpperEqual48;
assign UpperEqual39 = &(VAdr[63:38]) | ~|(VAdr[63:38]);
assign UpperEqual48 = &(VAdr[63:47]) | ~|(VAdr[63:47]);
assign UpperBitsUnequalPageFault = SV39Mode ? ~UpperEqual39 : ~UpperEqual48;
end else begin
assign SV39Mode = 0;
assign UpperBitsUnequalPageFault = 0;
end
endmodule