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Re: [RFC PATCH 8/8] target/i386: Move X86XSaveArea into TCG

From: Richard Henderson
Subject: Re: [RFC PATCH 8/8] target/i386: Move X86XSaveArea into TCG
Date: Tue, 6 Jul 2021 18:09:42 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 
On 7/5/21 3:46 AM, David Edmondson wrote:

Given that TCG is now the only consumer of X86XSaveArea, move the
structure definition and associated offset declarations and checks to a
TCG specific header.

Signed-off-by: David Edmondson <david.edmondson@oracle.com>
---
  target/i386/cpu.h            | 57 ------------------------------------
  target/i386/tcg/fpu_helper.c |  1 +
  target/i386/tcg/tcg-cpu.h    | 57 ++++++++++++++++++++++++++++++++++++
  3 files changed, 58 insertions(+), 57 deletions(-)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 96b672f8bd..0f7ddbfeae 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1305,48 +1305,6 @@ typedef struct XSavePKRU {
      uint32_t padding;
  } XSavePKRU;
-#define XSAVE_FCW_FSW_OFFSET 0x000 
-#define XSAVE_FTW_FOP_OFFSET    0x004
-#define XSAVE_CWD_RIP_OFFSET    0x008
-#define XSAVE_CWD_RDP_OFFSET    0x010
-#define XSAVE_MXCSR_OFFSET      0x018
-#define XSAVE_ST_SPACE_OFFSET   0x020
-#define XSAVE_XMM_SPACE_OFFSET  0x0a0
-#define XSAVE_XSTATE_BV_OFFSET  0x200
-#define XSAVE_AVX_OFFSET        0x240
-#define XSAVE_BNDREG_OFFSET     0x3c0
-#define XSAVE_BNDCSR_OFFSET     0x400
-#define XSAVE_OPMASK_OFFSET     0x440
-#define XSAVE_ZMM_HI256_OFFSET  0x480
-#define XSAVE_HI16_ZMM_OFFSET   0x680
-#define XSAVE_PKRU_OFFSET       0xa80
-
-typedef struct X86XSaveArea {
-    X86LegacyXSaveArea legacy;
-    X86XSaveHeader header;
-
-    /* Extended save areas: */
-
-    /* AVX State: */
-    XSaveAVX avx_state;
-
-    /* Ensure that XSaveBNDREG is properly aligned. */
-    uint8_t padding[XSAVE_BNDREG_OFFSET
-                    - sizeof(X86LegacyXSaveArea)
-                    - sizeof(X86XSaveHeader)
-                    - sizeof(XSaveAVX)];
-
-    /* MPX State: */
-    XSaveBNDREG bndreg_state;
-    XSaveBNDCSR bndcsr_state;
-    /* AVX-512 State: */
-    XSaveOpmask opmask_state;
-    XSaveZMM_Hi256 zmm_hi256_state;
-    XSaveHi16_ZMM hi16_zmm_state;
-    /* PKRU State: */
-    XSavePKRU pkru_state;
-} X86XSaveArea;
-
  QEMU_BUILD_BUG_ON(sizeof(XSaveAVX) != 0x100);
  QEMU_BUILD_BUG_ON(sizeof(XSaveBNDREG) != 0x40);
  QEMU_BUILD_BUG_ON(sizeof(XSaveBNDCSR) != 0x40);
@@ -1355,21 +1313,6 @@ QEMU_BUILD_BUG_ON(sizeof(XSaveZMM_Hi256) != 0x200);
  QEMU_BUILD_BUG_ON(sizeof(XSaveHi16_ZMM) != 0x400);
  QEMU_BUILD_BUG_ON(sizeof(XSavePKRU) != 0x8);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.fcw) != XSAVE_FCW_FSW_OFFSET); 
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.ftw) != XSAVE_FTW_FOP_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.fpip) != XSAVE_CWD_RIP_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.fpdp) != XSAVE_CWD_RDP_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.mxcsr) != XSAVE_MXCSR_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.fpregs) != 
XSAVE_ST_SPACE_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.xmm_regs) != 
XSAVE_XMM_SPACE_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, avx_state) != XSAVE_AVX_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, bndreg_state) != XSAVE_BNDREG_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, bndcsr_state) != XSAVE_BNDCSR_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, opmask_state) != XSAVE_OPMASK_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, zmm_hi256_state) != 
XSAVE_ZMM_HI256_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, hi16_zmm_state) != 
XSAVE_HI16_ZMM_OFFSET);
-QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, pkru_state) != XSAVE_PKRU_OFFSET);
-
  typedef struct ExtSaveArea {
      uint32_t feature, bits;
      uint32_t offset, size;
diff --git a/target/i386/tcg/fpu_helper.c b/target/i386/tcg/fpu_helper.c
index 4e11965067..74bbe94b80 100644
--- a/target/i386/tcg/fpu_helper.c
+++ b/target/i386/tcg/fpu_helper.c
@@ -20,6 +20,7 @@
  #include "qemu/osdep.h"
  #include <math.h>
  #include "cpu.h"
+#include "tcg-cpu.h"
  #include "exec/helper-proto.h"
  #include "fpu/softfloat.h"
  #include "fpu/softfloat-macros.h"
diff --git a/target/i386/tcg/tcg-cpu.h b/target/i386/tcg/tcg-cpu.h
index 36bd300af0..53a8494455 100644
--- a/target/i386/tcg/tcg-cpu.h
+++ b/target/i386/tcg/tcg-cpu.h
@@ -19,6 +19,63 @@
  #ifndef TCG_CPU_H
  #define TCG_CPU_H
+#define XSAVE_FCW_FSW_OFFSET 0x000 
+#define XSAVE_FTW_FOP_OFFSET    0x004
+#define XSAVE_CWD_RIP_OFFSET    0x008
+#define XSAVE_CWD_RDP_OFFSET    0x010
+#define XSAVE_MXCSR_OFFSET      0x018
+#define XSAVE_ST_SPACE_OFFSET   0x020
+#define XSAVE_XMM_SPACE_OFFSET  0x0a0
+#define XSAVE_XSTATE_BV_OFFSET  0x200
+#define XSAVE_AVX_OFFSET        0x240
+#define XSAVE_BNDREG_OFFSET     0x3c0
+#define XSAVE_BNDCSR_OFFSET     0x400
+#define XSAVE_OPMASK_OFFSET     0x440
+#define XSAVE_ZMM_HI256_OFFSET  0x480
+#define XSAVE_HI16_ZMM_OFFSET   0x680
+#define XSAVE_PKRU_OFFSET       0xa80
+
+typedef struct X86XSaveArea {
+    X86LegacyXSaveArea legacy;
+    X86XSaveHeader header;
+
+    /* Extended save areas: */
+
+    /* AVX State: */
+    XSaveAVX avx_state;
+
+    /* Ensure that XSaveBNDREG is properly aligned. */
+    uint8_t padding[XSAVE_BNDREG_OFFSET
+                    - sizeof(X86LegacyXSaveArea)
+                    - sizeof(X86XSaveHeader)
+                    - sizeof(XSaveAVX)];
+
+    /* MPX State: */
+    XSaveBNDREG bndreg_state;
+    XSaveBNDCSR bndcsr_state;
+    /* AVX-512 State: */
+    XSaveOpmask opmask_state;
+    XSaveZMM_Hi256 zmm_hi256_state;
+    XSaveHi16_ZMM hi16_zmm_state;
+    /* PKRU State: */
+    XSavePKRU pkru_state;
+} X86XSaveArea;
+
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.fcw) != XSAVE_FCW_FSW_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.ftw) != XSAVE_FTW_FOP_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.fpip) != XSAVE_CWD_RIP_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.fpdp) != XSAVE_CWD_RDP_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.mxcsr) != XSAVE_MXCSR_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.fpregs) != 
XSAVE_ST_SPACE_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, legacy.xmm_regs) != 
XSAVE_XMM_SPACE_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, avx_state) != XSAVE_AVX_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, bndreg_state) != XSAVE_BNDREG_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, bndcsr_state) != XSAVE_BNDCSR_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, opmask_state) != XSAVE_OPMASK_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, zmm_hi256_state) != 
XSAVE_ZMM_HI256_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, hi16_zmm_state) != 
XSAVE_HI16_ZMM_OFFSET);
+QEMU_BUILD_BUG_ON(offsetof(X86XSaveArea, pkru_state) != XSAVE_PKRU_OFFSET);
My only quibble is that these offsets are otherwise unused. This just becomes validation of compiler layout.
I presume that XSAVE_BNDREG_OFFSET is not merely ROUND_UP(offsetof(avx_state) + sizeof(avx_state), some_pow2)?
Do these offsets need to be migrated? Otherwise, how can one start a vm with kvm and then migrate to tcg? I presume the offsets above are constant for a given cpu, and that whatever cpu provides different offsets is not supported by tcg? Given the lack of avx, that's trivial these days... 


r~
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