From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Xen-devel <xen-devel@lists.xenproject.org>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
"Wei Liu" <wl@xen.org>, "Jan Beulich" <JBeulich@suse.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: [Xen-devel] [PATCH] x86/boot: Reposition trampoline data
Date: Mon, 19 Aug 2019 14:42:12 +0100 [thread overview]
Message-ID: <20190819134213.1628-3-andrew.cooper3@citrix.com> (raw)
In-Reply-To: <20190819134213.1628-1-andrew.cooper3@citrix.com>
... to separate code from data. In particular, trampoline_realmode_entry's
write to trampoline_cpu_started clobbers the I-cache line containing
trampoline_protmode_entry, which won't be great for AP startup.
Reformat the comments for trampoline_gdt to reduce their volume.
No functional change.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wl@xen.org>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
xen/arch/x86/boot/trampoline.S | 67 ++++++++++++++++++------------------------
1 file changed, 28 insertions(+), 39 deletions(-)
diff --git a/xen/arch/x86/boot/trampoline.S b/xen/arch/x86/boot/trampoline.S
index 1761fc1213..1b11b4757a 100644
--- a/xen/arch/x86/boot/trampoline.S
+++ b/xen/arch/x86/boot/trampoline.S
@@ -59,45 +59,6 @@ GLOBAL(trampoline_realmode_entry)
lmsw %ax # CR0.PE = 1 (enter protected mode)
ljmpl $BOOT_CS32,$bootsym_rel(trampoline_protmode_entry,6)
-trampoline_gdt:
- /* 0x0000: unused */
- .quad 0x0000000000000000
- /* 0x0008: ring 0 code, 32-bit mode */
- .quad 0x00cf9b000000ffff
- /* 0x0010: ring 0 code, 64-bit mode */
- .quad 0x00af9b000000ffff
- /* 0x0018: ring 0 data */
- .quad 0x00cf93000000ffff
- /* 0x0020: real-mode code @ BOOT_TRAMPOLINE */
- .long 0x0000ffff
- .long 0x00009b00
- /* 0x0028: real-mode data @ BOOT_TRAMPOLINE */
- .long 0x0000ffff
- .long 0x00009300
- /*
- * 0x0030: ring 0 Xen data, 16 MiB size, base
- * address is computed at runtime.
- */
- .quad 0x00c0930000000fff
-.Ltramopline_gdt_end:
-
- .pushsection .trampoline_rel, "a"
- .long trampoline_gdt + BOOT_PSEUDORM_CS + 2 - .
- .long trampoline_gdt + BOOT_PSEUDORM_DS + 2 - .
- .popsection
-
-GLOBAL(trampoline_misc_enable_off)
- .quad 0
-
-GLOBAL(cpuid_ext_features)
- .long 0
-
-GLOBAL(trampoline_xen_phys_start)
- .long 0
-
-GLOBAL(trampoline_cpu_started)
- .byte 0
-
.code32
trampoline_protmode_entry:
/* Set up a few descriptors: on entry only CS is guaranteed good. */
@@ -186,6 +147,34 @@ idt_48: .word 0, 0, 0 # base = limit = 0
gdt_48: .word .Ltramopline_gdt_end - trampoline_gdt - 1
.long bootsym_rel(trampoline_gdt,4)
+trampoline_gdt:
+ .quad 0x0000000000000000 /* 0x0000: unused */
+ .quad 0x00cf9b000000ffff /* 0x0008: ring 0 code, 32-bit mode */
+ .quad 0x00af9b000000ffff /* 0x0010: ring 0 code, 64-bit mode */
+ .quad 0x00cf93000000ffff /* 0x0018: ring 0 data */
+ .quad 0x00009b000000ffff /* 0x0020: real-mode code @ BOOT_TRAMPOLINE */
+ .quad 0x000093000000ffff /* 0x0028: real-mode data @ BOOT_TRAMPOLINE */
+ .quad 0x00c0930000000fff /* 0x0030: ring 0 Xen data, 16M @ XEN */
+.Ltramopline_gdt_end:
+
+ /* Relocations for trampoline Real Mode segments. */
+ .pushsection .trampoline_rel, "a"
+ .long trampoline_gdt + BOOT_PSEUDORM_CS + 2 - .
+ .long trampoline_gdt + BOOT_PSEUDORM_DS + 2 - .
+ .popsection
+
+GLOBAL(trampoline_misc_enable_off)
+ .quad 0
+
+GLOBAL(cpuid_ext_features)
+ .long 0
+
+GLOBAL(trampoline_xen_phys_start)
+ .long 0
+
+GLOBAL(trampoline_cpu_started)
+ .byte 0
+
/* The first page of trampoline is permanent, the rest boot-time only. */
/* Reuse the boot trampoline on the 1st trampoline page as stack for wakeup. */
.equ wakeup_stack, trampoline_start + PAGE_SIZE
--
2.11.0
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next prev parent reply other threads:[~2019-08-19 13:42 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-19 13:42 [Xen-devel] [PATCH] x86/boot: Various bits of trampoline cleanup Andrew Cooper
2019-08-19 13:42 ` [Xen-devel] [PATCH] x86/boot: Further minor GDT corrections Andrew Cooper
2019-08-27 14:49 ` Jan Beulich
2019-08-19 13:42 ` Andrew Cooper [this message]
2019-08-19 16:02 ` [Xen-devel] [PATCH] x86/boot: Reposition trampoline data David Woodhouse
2019-08-27 14:50 ` Jan Beulich
2019-08-19 13:42 ` [Xen-devel] [PATCH] x86/boot: Drop all use of lmsw Andrew Cooper
2019-08-27 14:52 ` Jan Beulich
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