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antonblanchard.microwatt/mmu.vhdl
Paul Mackerras c938246cc8 dcache: Simplify addressing of the dcache TLB 
Instead of having TLB invalidation and TLB load requests come through
the dcache main path, these operations are now done in one cycle
entirely based on signals from the MMU, and don't involve the TLB read
path or the dcache state machine at all.  So that we know which way of
the TLB to affect for invalidations, loadstore1 now sends down a "TLB
probe" operation for tlbie instructions which goes through the dcache
pipeline and sets the r1.tlb_hit_* fields which are used in the
subsequent invalidation operation from the MMU (if it is a single-page
invalidation).  TLB load operations write to the way identified by
r1.victim_way, which was set on the TLB miss that triggered the TLB
reload.

Since we are writing just one way of the TLB tags now, rather than
writing all ways with one way's value changed, we now pad each way to
a multiple of 8 bits so that byte write-enables can be used to select
which way gets written.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
2025-04-09 09:50:15 +10:00

505 lines
18 KiB
VHDL
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library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
library work;
use work.common.all;
-- Radix MMU
-- Supports 4-level trees as in arch 3.0B, but not the two-step translation for
-- guests under a hypervisor (i.e. there is no gRA -> hRA translation).
entity mmu is
port (
clk : in std_ulogic;
rst : in std_ulogic;
l_in : in Loadstore1ToMmuType;
l_out : out MmuToLoadstore1Type;
d_out : out MmuToDcacheType;
d_in : in DcacheToMmuType;
i_out : out MmuToITLBType
);
end mmu;
architecture behave of mmu is
type state_t is (IDLE,
DO_TLBIE,
PART_TBL_READ,
PART_TBL_WAIT,
PART_TBL_DONE,
PROC_TBL_READ,
PROC_TBL_WAIT,
SEGMENT_CHECK,
RADIX_LOOKUP,
RADIX_READ_WAIT,
RADIX_LOAD_TLB,
RADIX_FINISH
);
type reg_stage_t is record
-- latched request from loadstore1
valid : std_ulogic;
iside : std_ulogic;
store : std_ulogic;
priv : std_ulogic;
addr : std_ulogic_vector(63 downto 0);
inval_all : std_ulogic;
-- config SPRs
ptcr : std_ulogic_vector(63 downto 0);
pid : std_ulogic_vector(31 downto 0);
-- internal state
state : state_t;
done : std_ulogic;
err : std_ulogic;
prtbl : std_ulogic_vector(63 downto 0);
ptb_valid : std_ulogic;
pgtbl0 : std_ulogic_vector(63 downto 0);
pt0_valid : std_ulogic;
pgtbl3 : std_ulogic_vector(63 downto 0);
pt3_valid : std_ulogic;
shift : unsigned(5 downto 0);
mask_size : unsigned(4 downto 0);
pgbase : std_ulogic_vector(55 downto 0);
pde : std_ulogic_vector(63 downto 0);
invalid : std_ulogic;
badtree : std_ulogic;
segerror : std_ulogic;
perm_err : std_ulogic;
rc_error : std_ulogic;
end record;
signal r, rin : reg_stage_t;
signal addrsh : std_ulogic_vector(15 downto 0);
signal mask : std_ulogic_vector(15 downto 0);
signal finalmask : std_ulogic_vector(43 downto 0);
begin
-- Multiplex internal SPR values back to loadstore1, selected
-- by l_in.sprnf.
l_out.sprval <= r.ptcr when l_in.sprnf = '1' else x"00000000" & r.pid;
mmu_0: process(clk)
begin
if rising_edge(clk) then
if rst = '1' then
r.state <= IDLE;
r.valid <= '0';
r.ptb_valid <= '0';
r.pt0_valid <= '0';
r.pt3_valid <= '0';
r.ptcr <= (others => '0');
r.pid <= (others => '0');
else
if rin.valid = '1' then
report "MMU got tlb miss for " & to_hstring(rin.addr);
end if;
if l_out.done = '1' then
report "MMU completing op without error";
end if;
if l_out.err = '1' then
report "MMU completing op with err invalid=" & std_ulogic'image(l_out.invalid) &
" badtree=" & std_ulogic'image(l_out.badtree);
end if;
if rin.state = RADIX_LOOKUP then
report "radix lookup shift=" & integer'image(to_integer(rin.shift)) &
" msize=" & integer'image(to_integer(rin.mask_size));
end if;
if r.state = RADIX_LOOKUP then
report "send load addr=" & to_hstring(d_out.addr) &
" addrsh=" & to_hstring(addrsh) & " mask=" & to_hstring(mask);
end if;
r <= rin;
end if;
end if;
end process;
-- Shift address bits 61--12 right by 0--47 bits and
-- supply the least significant 16 bits of the result.
addrshifter: process(all)
variable sh1 : std_ulogic_vector(30 downto 0);
variable sh2 : std_ulogic_vector(18 downto 0);
variable result : std_ulogic_vector(15 downto 0);
begin
case r.shift(5 downto 4) is
when "00" =>
sh1 := r.addr(42 downto 12);
when "01" =>
sh1 := r.addr(58 downto 28);
when others =>
sh1 := "0000000000000" & r.addr(61 downto 44);
end case;
case r.shift(3 downto 2) is
when "00" =>
sh2 := sh1(18 downto 0);
when "01" =>
sh2 := sh1(22 downto 4);
when "10" =>
sh2 := sh1(26 downto 8);
when others =>
sh2 := sh1(30 downto 12);
end case;
case r.shift(1 downto 0) is
when "00" =>
result := sh2(15 downto 0);
when "01" =>
result := sh2(16 downto 1);
when "10" =>
result := sh2(17 downto 2);
when others =>
result := sh2(18 downto 3);
end case;
addrsh <= result;
end process;
-- generate mask for extracting address fields for PTE address generation
addrmaskgen: process(all)
variable m : std_ulogic_vector(15 downto 0);
begin
-- mask_count has to be >= 5
m := x"001f";
if is_X(r.mask_size) then
m := (others => 'X');
else
for i in 5 to 15 loop
if i < to_integer(r.mask_size) then
m(i) := '1';
end if;
end loop;
end if;
mask <= m;
end process;
-- generate mask for extracting address bits to go in TLB entry
-- in order to support pages > 4kB
finalmaskgen: process(all)
variable m : std_ulogic_vector(43 downto 0);
begin
m := (others => '0');
for i in 0 to 43 loop
if is_X(r.shift) then
m(i) := 'X';
elsif i < to_integer(r.shift) then
m(i) := '1';
end if;
end loop;
finalmask <= m;
end process;
mmu_1: process(all)
variable v : reg_stage_t;
variable dcreq : std_ulogic;
variable tlb_load : std_ulogic;
variable tlbie_req : std_ulogic;
variable ptbl_rd : std_ulogic;
variable prtbl_rd : std_ulogic;
variable pt_valid : std_ulogic;
variable effpid : std_ulogic_vector(31 downto 0);
variable prtable_addr : std_ulogic_vector(63 downto 0);
variable rts : unsigned(5 downto 0);
variable mbits : unsigned(5 downto 0);
variable pgtable_addr : std_ulogic_vector(63 downto 0);
variable pte : std_ulogic_vector(63 downto 0);
variable tlb_data : std_ulogic_vector(63 downto 0);
variable nonzero : std_ulogic;
variable pgtbl : std_ulogic_vector(63 downto 0);
variable perm_ok : std_ulogic;
variable rc_ok : std_ulogic;
variable addr : std_ulogic_vector(63 downto 0);
variable data : std_ulogic_vector(63 downto 0);
begin
v := r;
v.valid := '0';
dcreq := '0';
v.done := '0';
v.err := '0';
v.invalid := '0';
v.badtree := '0';
v.segerror := '0';
v.perm_err := '0';
v.rc_error := '0';
tlb_load := '0';
tlbie_req := '0';
v.inval_all := '0';
ptbl_rd := '0';
prtbl_rd := '0';
-- Radix tree data structures in memory are big-endian,
-- so we need to byte-swap them
for i in 0 to 7 loop
data(i * 8 + 7 downto i * 8) := d_in.data((7 - i) * 8 + 7 downto (7 - i) * 8);
end loop;
case r.state is
when IDLE =>
if l_in.addr(63) = '0' then
pgtbl := r.pgtbl0;
pt_valid := r.pt0_valid;
else
pgtbl := r.pgtbl3;
pt_valid := r.pt3_valid;
end if;
-- rts == radix tree size, # address bits being translated
rts := unsigned('0' & pgtbl(62 downto 61) & pgtbl(7 downto 5));
-- mbits == # address bits to index top level of tree
mbits := unsigned('0' & pgtbl(4 downto 0));
-- set v.shift to rts so that we can use finalmask for the segment check
v.shift := rts;
v.mask_size := mbits(4 downto 0);
v.pgbase := pgtbl(55 downto 8) & x"00";
if l_in.valid = '1' then
v.addr := l_in.addr;
v.iside := l_in.iside;
v.store := not (l_in.load or l_in.iside);
v.priv := l_in.priv;
if l_in.tlbie = '1' then
-- Invalidate all iTLB/dTLB entries for tlbie with
-- RB[IS] != 0 or RB[AP] != 0, or for slbia
v.inval_all := l_in.slbia or l_in.addr(11) or l_in.addr(10) or
l_in.addr(7) or l_in.addr(6) or l_in.addr(5);
-- RIC=2 or 3 flushes process table caches.
if l_in.ric(1) = '1' then
v.pt0_valid := '0';
v.pt3_valid := '0';
v.ptb_valid := '0';
end if;
v.state := DO_TLBIE;
else
v.valid := '1';
if r.ptb_valid = '0' then
-- need to fetch process table base from partition table
v.state := PART_TBL_READ;
elsif pt_valid = '0' then
-- need to fetch process table entry
-- set v.shift so we can use finalmask for generating
-- the process table entry address
v.shift := unsigned('0' & r.prtbl(4 downto 0));
v.state := PROC_TBL_READ;
elsif mbits = 0 then
-- Use RPDS = 0 to disable radix tree walks
v.state := RADIX_FINISH;
v.invalid := '1';
else
v.state := SEGMENT_CHECK;
end if;
end if;
end if;
if l_in.mtspr = '1' then
-- Move to PID needs to invalidate L1 TLBs and cached
-- pgtbl0 value. Move to PTCR does that plus
-- invalidating the cached pgtbl3 and prtbl values as well.
if l_in.sprnt = '0' then
v.pid := l_in.rs(31 downto 0);
else
v.ptcr := l_in.rs;
v.pt3_valid := '0';
v.ptb_valid := '0';
end if;
v.pt0_valid := '0';
v.inval_all := '1';
v.state := DO_TLBIE;
end if;
when DO_TLBIE =>
tlbie_req := '1';
v.state := RADIX_FINISH;
when PART_TBL_READ =>
dcreq := '1';
ptbl_rd := '1';
v.state := PART_TBL_WAIT;
when PART_TBL_WAIT =>
if d_in.done = '1' then
v.prtbl := data;
v.ptb_valid := '1';
v.state := PART_TBL_DONE;
end if;
when PART_TBL_DONE =>
v.shift := unsigned('0' & r.prtbl(4 downto 0));
v.state := PROC_TBL_READ;
when PROC_TBL_READ =>
dcreq := '1';
prtbl_rd := '1';
v.state := PROC_TBL_WAIT;
when PROC_TBL_WAIT =>
if d_in.done = '1' then
if r.addr(63) = '1' then
v.pgtbl3 := data;
v.pt3_valid := '1';
else
v.pgtbl0 := data;
v.pt0_valid := '1';
end if;
-- rts == radix tree size, # address bits being translated
rts := unsigned('0' & data(62 downto 61) & data(7 downto 5));
-- mbits == # address bits to index top level of tree
mbits := unsigned('0' & data(4 downto 0));
-- set v.shift to rts so that we can use finalmask for the segment check
v.shift := rts;
v.mask_size := mbits(4 downto 0);
v.pgbase := data(55 downto 8) & x"00";
if mbits = 0 then
v.state := RADIX_FINISH;
v.invalid := '1';
else
v.state := SEGMENT_CHECK;
end if;
end if;
if d_in.err = '1' then
v.state := RADIX_FINISH;
v.badtree := '1';
end if;
when SEGMENT_CHECK =>
mbits := '0' & r.mask_size;
v.shift := r.shift + (31 - 12) - mbits;
nonzero := or(r.addr(61 downto 31) and not finalmask(30 downto 0));
if r.addr(63) /= r.addr(62) or nonzero = '1' then
v.state := RADIX_FINISH;
v.segerror := '1';
elsif mbits < 5 or mbits > 16 or mbits > (r.shift + (31 - 12)) then
v.state := RADIX_FINISH;
v.badtree := '1';
else
v.state := RADIX_LOOKUP;
end if;
when RADIX_LOOKUP =>
dcreq := '1';
v.state := RADIX_READ_WAIT;
when RADIX_READ_WAIT =>
if d_in.done = '1' then
v.pde := data;
-- test valid bit
if data(63) = '1' then
-- test leaf bit
if data(62) = '1' then
-- check permissions and RC bits
perm_ok := '0';
if r.priv = '1' or data(3) = '0' then
if r.iside = '0' then
perm_ok := data(1) or (data(2) and not r.store);
else
-- no IAMR, so no KUEP support for now
-- deny execute permission if cache inhibited
perm_ok := data(0) and not data(5);
end if;
end if;
rc_ok := data(8) and (data(7) or not r.store);
if perm_ok = '1' and rc_ok = '1' then
v.state := RADIX_LOAD_TLB;
else
v.state := RADIX_FINISH;
v.perm_err := not perm_ok;
-- permission error takes precedence over RC error
v.rc_error := perm_ok;
end if;
else
mbits := unsigned('0' & data(4 downto 0));
if mbits < 5 or mbits > 16 or mbits > r.shift then
v.state := RADIX_FINISH;
v.badtree := '1';
else
v.shift := v.shift - mbits;
v.mask_size := mbits(4 downto 0);
v.pgbase := data(55 downto 8) & x"00";
v.state := RADIX_LOOKUP;
end if;
end if;
else
-- non-present PTE, generate a DSI
v.state := RADIX_FINISH;
v.invalid := '1';
end if;
end if;
if d_in.err = '1' then
v.state := RADIX_FINISH;
v.badtree := '1';
end if;
when RADIX_LOAD_TLB =>
tlb_load := '1';
v.state := RADIX_FINISH;
when RADIX_FINISH =>
v.state := IDLE;
end case;
if v.state = RADIX_FINISH then
v.err := v.invalid or v.badtree or v.segerror or v.perm_err or v.rc_error;
v.done := not v.err;
end if;
if r.addr(63) = '1' then
effpid := x"00000000";
else
effpid := r.pid;
end if;
prtable_addr := x"00" & r.prtbl(55 downto 36) &
((r.prtbl(35 downto 12) and not finalmask(23 downto 0)) or
(effpid(31 downto 8) and finalmask(23 downto 0))) &
effpid(7 downto 0) & "0000";
pgtable_addr := x"00" & r.pgbase(55 downto 19) &
((r.pgbase(18 downto 3) and not mask) or (addrsh and mask)) &
"000";
pte := x"00" &
((r.pde(55 downto 12) and not finalmask) or (r.addr(55 downto 12) and finalmask))
& r.pde(11 downto 0);
-- update registers
rin <= v;
-- drive outputs
if tlbie_req = '1' then
addr := r.addr;
tlb_data := (others => '0');
elsif tlb_load = '1' then
addr := r.addr(63 downto 12) & x"000";
tlb_data := pte;
elsif ptbl_rd = '1' then
addr := x"00" & r.ptcr(55 downto 12) & x"008";
tlb_data := (others => '0');
elsif prtbl_rd = '1' then
addr := prtable_addr;
tlb_data := (others => '0');
else
addr := pgtable_addr;
tlb_data := (others => '0');
end if;
l_out.done <= r.done;
l_out.err <= r.err;
l_out.invalid <= r.invalid;
l_out.badtree <= r.badtree;
l_out.segerr <= r.segerror;
l_out.perm_error <= r.perm_err;
l_out.rc_error <= r.rc_error;
d_out.valid <= dcreq;
d_out.tlbie <= tlbie_req;
d_out.doall <= r.inval_all;
d_out.tlbld <= tlb_load and not r.iside;
d_out.addr <= addr;
d_out.pte <= tlb_data;
i_out.tlbld <= tlb_load and r.iside;
i_out.tlbie <= tlbie_req;
i_out.doall <= r.inval_all;
i_out.addr <= addr;
i_out.pte <= tlb_data;
end process;
end;
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