From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Xen-devel <xen-devel@lists.xen.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Jan Beulich <JBeulich@suse.com>
Subject: [PATCH] x86/emul: Split exception handling out of invoke_stub()
Date: Wed, 24 Jan 2018 18:16:45 +0000 [thread overview]
Message-ID: <1516817805-13702-1-git-send-email-andrew.cooper3@citrix.com> (raw)
For a release build, bloat-o-meter reports:
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-5111 (-5111)
function old new delta
x86_emulate 126458 121347 -5111
or in other words, a 4% redunction in code size from this change alone.
While shuffling things around, drop the use of __LINE__, and print the
instruction stream hexdump at WARNING as well.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
I stubled onto this while looking at the domain_crash() side of things. It
appears that your AVX series makes the problem more pronounced, due to more
codepaths using invoke_stub().
---
xen/arch/x86/x86_emulate/x86_emulate.c | 33 +++++++++++++++++++--------------
1 file changed, 19 insertions(+), 14 deletions(-)
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
index ff0a003..6dccf4e 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -866,7 +866,7 @@ static inline int mkec(uint8_t e, int32_t ec, ...)
#ifdef __XEN__
# define invoke_stub(pre, post, constraints...) do { \
- union stub_exception_token res_ = { .raw = ~0 }; \
+ stub_exn_info = (union stub_exception_token) { .raw = ~0 }; \
asm volatile ( pre "\n\tINDIRECT_CALL %[stub]\n\t" post "\n" \
".Lret%=:\n\t" \
".pushsection .fixup,\"ax\"\n" \
@@ -875,21 +875,11 @@ static inline int mkec(uint8_t e, int32_t ec, ...)
"jmp .Lret%=\n\t" \
".popsection\n\t" \
_ASM_EXTABLE(.Lret%=, .Lfix%=) \
- : [exn] "+g" (res_), constraints, \
+ : [exn] "+g" (stub_exn_info), constraints, \
[stub] "r" (stub.func), \
"m" (*(uint8_t(*)[MAX_INST_LEN + 1])stub.ptr) ); \
- if ( unlikely(~res_.raw) ) \
- { \
- gprintk(XENLOG_WARNING, \
- "exception %u (ec=%04x) in emulation stub (line %u)\n", \
- res_.fields.trapnr, res_.fields.ec, __LINE__); \
- gprintk(XENLOG_INFO, "stub: %"__stringify(MAX_INST_LEN)"ph\n", \
- stub.func); \
- generate_exception_if(res_.fields.trapnr == EXC_UD, EXC_UD); \
- domain_crash(current->domain); \
- rc = X86EMUL_UNHANDLEABLE; \
- goto done; \
- } \
+ if ( unlikely(~stub_exn_info.raw) ) \
+ goto emulation_stub_failure; \
} while (0)
#else
# define invoke_stub(pre, post, constraints...) \
@@ -3000,6 +2990,9 @@ x86_emulate(
struct fpu_insn_ctxt fic = { .type = X86EMUL_FPU_none, .exn_raised = -1 };
struct x86_emulate_stub stub = {};
DECLARE_ALIGNED(mmval_t, mmval);
+#ifdef __XEN__
+ union stub_exception_token stub_exn_info;
+#endif
ASSERT(ops->read);
@@ -8012,6 +8005,18 @@ x86_emulate(
put_stub(stub);
return rc;
#undef state
+
+#ifdef __XEN__
+ emulation_stub_failure:
+ gprintk(XENLOG_WARNING, "exception %u (ec=%04x) in emulation stub\n",
+ stub_exn_info.fields.trapnr, stub_exn_info.fields.ec);
+ gprintk(XENLOG_WARNING, " stub: %"__stringify(MAX_INST_LEN)"ph\n",
+ stub.func);
+ generate_exception_if(stub_exn_info.fields.trapnr == EXC_UD, EXC_UD);
+ domain_crash(current->domain);
+ rc = X86EMUL_UNHANDLEABLE;
+ goto done;
+#endif
}
#undef op_bytes
--
2.1.4
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next reply other threads:[~2018-01-24 18:16 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-24 18:16 Andrew Cooper [this message]
2018-01-25 10:49 ` [PATCH] x86/emul: Split exception handling out of invoke_stub() Jan Beulich
2018-01-25 11:09 ` Andrew Cooper
2018-01-25 11:41 ` Jan Beulich
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