fetch1: Fix bug where BTC entries don't match on MSR[IR]

This fixes a bug in the BTC where entries created for a given address
when MSR[IR] = 0 are used when MSR[IR] = 1 and vice-versa.  The fix is
to include r.virt_mode (which mirrors MSR[IR]) in the tag portion of
the BTC.

Fixes: 0fb207be60 ("fetch1: Implement a simple branch target cache", 2020-12-19)
Reported-by: Anton Blanchard <anton@linux.ibm.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
pull/392/head^2
Paul Mackerras 2 years ago
parent 2562053af3
commit 769f5c3a53

@ -53,7 +53,7 @@ architecture behaviour of fetch1 is
constant BTC_TAG_BITS : integer := 62 - BTC_ADDR_BITS;
constant BTC_TARGET_BITS : integer := 62;
constant BTC_SIZE : integer := 2 ** BTC_ADDR_BITS;
constant BTC_WIDTH : integer := BTC_TAG_BITS + BTC_TARGET_BITS + 1;
constant BTC_WIDTH : integer := BTC_TAG_BITS + BTC_TARGET_BITS + 2;
type btc_mem_type is array (0 to BTC_SIZE - 1) of std_ulogic_vector(BTC_WIDTH - 1 downto 0);

signal btc_rd_data : std_ulogic_vector(BTC_WIDTH - 1 downto 0) := (others => '0');
@ -111,6 +111,7 @@ begin
signal btc_wr_addr : std_ulogic_vector(BTC_ADDR_BITS - 1 downto 0);
begin
btc_wr_data <= w_in.br_taken &
r.virt_mode &
w_in.br_nia(63 downto BTC_ADDR_BITS + 2) &
w_in.redirect_nia(63 downto 2);
btc_wr_addr <= w_in.br_nia(BTC_ADDR_BITS + 1 downto 2);
@ -193,7 +194,8 @@ begin
v.nia(63 downto 32) := x"00000000";
end if;
if btc_rd_valid = '1' and r_int.rd_is_niap4 = '1' and
btc_rd_data(BTC_WIDTH - 2 downto BTC_TARGET_BITS)
btc_rd_data(BTC_WIDTH - 2) = r.virt_mode and
btc_rd_data(BTC_WIDTH - 3 downto BTC_TARGET_BITS)
= v.nia(BTC_TAG_BITS + BTC_ADDR_BITS + 1 downto BTC_ADDR_BITS + 2) then
v_int.predicted_taken := btc_rd_data(BTC_WIDTH - 1);
v_int.pred_not_taken := not btc_rd_data(BTC_WIDTH - 1);

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