On 7/10/24 11:42, Clément Chigot wrote:
Hi Mark,
This patch introduces regressions in our x86_64 VxWorks kernels
running over qemu. Some page faults are triggered randomly.
Earlier to this patch, the MemOp `ot` passed to `gen_op_st_v` was the
`gen_pop_T0` created a few lines above.
Now, this is `op->ot` which comes from elsewhere.
Adding `op->ot = ot` just before calling `gen_writeback` fixes my
regressions. But I'm wondering if there could be some unexpected
fallbacks, `op->ot` possibly being used afterwards.
Mark's patch is correct and the (previously latent) mistake is in
the decoding table.
The manual correctly says that POP has "default 64-bit" operand;
that is, it is 64-bit even without a REX.W prefix. It must be
marked as "d64" rather than "v".
Can you test this patch?
diff --git a/target/i386/tcg/decode-new.c.inc b/target/i386/tcg/decode-new.c.inc
index 0d846c32c22..d2da1d396d5 100644
--- a/target/i386/tcg/decode-new.c.inc
+++ b/target/i386/tcg/decode-new.c.inc
@@ -1717,7 +1717,7 @@ static const X86OpEntry opcodes_root[256] = {
[0x8C] = X86_OP_ENTRYwr(MOV, E,v, S,w, op0_Mw),
[0x8D] = X86_OP_ENTRYwr(LEA, G,v, M,v, nolea),
[0x8E] = X86_OP_ENTRYwr(MOV, S,w, E,w),
- [0x8F] = X86_OP_GROUPw(group1A, E,v),
+ [0x8F] = X86_OP_GROUPw(group1A, E,d64),
[0x98] = X86_OP_ENTRY1(CBW, 0,v), /* rAX */
[0x99] = X86_OP_ENTRYwr(CWD, 2,v, 0,v), /* rDX, rAX */
diff --git a/target/i386/tcg/emit.c.inc b/target/i386/tcg/emit.c.inc
index fc7477833bc..36bb308e449 100644
--- a/target/i386/tcg/emit.c.inc
+++ b/target/i386/tcg/emit.c.inc
@@ -2788,6 +2788,8 @@ static void gen_POP(DisasContext *s, X86DecodedInsn
*decode)
X86DecodedOp *op = &decode->op[0];
MemOp ot = gen_pop_T0(s);
+ /* Only 16/32-bit access in 32-bit mode, 16/64-bit access in long mode. */
+ assert(ot == op->ot);
if (op->has_ea || op->unit == X86_OP_SEG) {
/* NOTE: order is important for MMU exceptions */
gen_writeback(s, decode, 0, s->T0);
Thanks (and it's reassuring that everything else has worked fine
for you!),
Paolo
Thanks,
Clément
On Sat, Jun 8, 2024 at 10:36 AM Paolo Bonzini <pbonz...@redhat.com> wrote:
From: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk>
Instead of directly implementing the writeback using gen_op_st_v(), use the
existing gen_writeback() function.
Suggested-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk>
Message-ID: <20240606095319.229650-3-mark.cave-ayl...@ilande.co.uk>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
target/i386/tcg/emit.c.inc | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/target/i386/tcg/emit.c.inc b/target/i386/tcg/emit.c.inc
index ca78504b6e4..6123235c000 100644
--- a/target/i386/tcg/emit.c.inc
+++ b/target/i386/tcg/emit.c.inc
@@ -2580,9 +2580,9 @@ static void gen_POP(DisasContext *s, CPUX86State *env,
X86DecodedInsn *decode)
if (op->has_ea) {
/* NOTE: order is important for MMU exceptions */
- gen_op_st_v(s, ot, s->T0, s->A0);
- op->unit = X86_OP_SKIP;
+ gen_writeback(s, decode, 0, s->T0);
}
+
/* NOTE: writing back registers after update is important for pop %sp */
gen_pop_update(s, ot);
}
--
2.45.1
