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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] x86emul: support LKGS
commit a6b143e5a3a5733c12b71e7e2f5b6e9300e5920a
Author: Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue May 12 08:31:59 2026 +0200
Commit: Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue May 12 08:31:59 2026 +0200
x86emul: support LKGS
Provide support for this insn, which is a prereq to FRED. CPUID-wise,
while its and FRED's enumerators were already introduced, their dependency
still needs adding.
While adding a testcase, also add a SWAPGS one. In order to not affect
the behavior of pre-existing tests, install write_{segment,msr} hooks
only transiently.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
tools/tests/x86_emulator/predicates.c | 1 +
tools/tests/x86_emulator/test_x86_emulator.c | 96 ++++++++++++++++++++++++++++
tools/tests/x86_emulator/x86-emulate.c | 1 +
xen/arch/x86/x86_emulate/decode.c | 6 +-
xen/arch/x86/x86_emulate/private.h | 1 +
xen/arch/x86/x86_emulate/x86_emulate.c | 33 +++++++++-
xen/tools/gen-cpuid.py | 3 +-
7 files changed, 137 insertions(+), 4 deletions(-)
diff --git a/tools/tests/x86_emulator/predicates.c
b/tools/tests/x86_emulator/predicates.c
index 019c2ced8a..8ff2653895 100644
--- a/tools/tests/x86_emulator/predicates.c
+++ b/tools/tests/x86_emulator/predicates.c
@@ -326,6 +326,7 @@ static const struct {
{ { 0x00, 0x18 }, { 2, 2 }, T, R }, /* ltr */
{ { 0x00, 0x20 }, { 2, 2 }, T, R }, /* verr */
{ { 0x00, 0x28 }, { 2, 2 }, T, R }, /* verw */
+ { { 0x00, 0x30 }, { 0, 2 }, T, R, pfx_f2 }, /* lkgs */
{ { 0x01, 0x00 }, { 2, 2 }, F, W }, /* sgdt */
{ { 0x01, 0x08 }, { 2, 2 }, F, W }, /* sidt */
{ { 0x01, 0x10 }, { 2, 2 }, F, R }, /* lgdt */
diff --git a/tools/tests/x86_emulator/test_x86_emulator.c
b/tools/tests/x86_emulator/test_x86_emulator.c
index 20929b80c6..af29b106f1 100644
--- a/tools/tests/x86_emulator/test_x86_emulator.c
+++ b/tools/tests/x86_emulator/test_x86_emulator.c
@@ -673,6 +673,10 @@ static int blk(
return x86_emul_blk((void *)offset, p_data, bytes, eflags, state, ctxt);
}
+#ifdef __x86_64__
+static unsigned long gs_base, gs_base_shadow;
+#endif
+
static int read_segment(
enum x86_segment seg,
struct segment_register *reg,
@@ -682,9 +686,26 @@ static int read_segment(
return X86EMUL_UNHANDLEABLE;
memset(reg, 0, sizeof(*reg));
reg->p = 1;
+
return X86EMUL_OKAY;
}
+#ifdef __x86_64__
+static int write_segment(
+ enum x86_segment seg,
+ const struct segment_register *reg,
+ struct x86_emulate_ctxt *ctxt)
+{
+ if ( !is_x86_user_segment(seg) )
+ return X86EMUL_UNHANDLEABLE;
+
+ if ( seg == x86_seg_gs )
+ gs_base = reg->base;
+
+ return X86EMUL_OKAY;
+}
+#endif
+
static int read_msr(
unsigned int reg,
uint64_t *val,
@@ -696,6 +717,20 @@ static int read_msr(
*val = ctxt->addr_size > 32 ? EFER_LME | EFER_LMA : 0;
return X86EMUL_OKAY;
+#ifdef __x86_64__
+ case MSR_GS_BASE:
+ if ( ctxt->addr_size < 64 )
+ break;
+ *val = gs_base;
+ return X86EMUL_OKAY;
+
+ case MSR_SHADOW_GS_BASE:
+ if ( ctxt->addr_size < 64 )
+ break;
+ *val = gs_base_shadow;
+ return X86EMUL_OKAY;
+#endif
+
case MSR_TSC_AUX:
#define TSC_AUX_VALUE 0xCACACACA
*val = TSC_AUX_VALUE;
@@ -705,6 +740,32 @@ static int read_msr(
return X86EMUL_UNHANDLEABLE;
}
+#ifdef __x86_64__
+static int write_msr(
+ unsigned int reg,
+ uint64_t val,
+ struct x86_emulate_ctxt *ctxt,
+ bool explicit)
+{
+ switch ( reg )
+ {
+ case MSR_GS_BASE:
+ if ( ctxt->addr_size < 64 || !is_canonical_address(val) )
+ break;
+ gs_base = val;
+ return X86EMUL_OKAY;
+
+ case MSR_SHADOW_GS_BASE:
+ if ( ctxt->addr_size < 64 || !is_canonical_address(val) )
+ break;
+ gs_base_shadow = val;
+ return X86EMUL_OKAY;
+ }
+
+ return X86EMUL_UNHANDLEABLE;
+}
+#endif
+
#define INVPCID_ADDR 0x12345678
#define INVPCID_PCID 0x123
@@ -1339,6 +1400,41 @@ int main(int argc, char **argv)
printf("%u bytes read - ", bytes_read);
goto fail;
}
+ printf("okay\n");
+
+ emulops.write_segment = write_segment;
+ emulops.write_msr = write_msr;
+
+ printf("%-40s", "Testing swapgs...");
+ instr[0] = 0x0f; instr[1] = 0x01; instr[2] = 0xf8;
+ regs.eip = (unsigned long)&instr[0];
+ gs_base = 0xffffeeeecccc8888UL;
+ gs_base_shadow = 0x0000111122224444UL;
+ rc = x86_emulate(&ctxt, &emulops);
+ if ( (rc != X86EMUL_OKAY) ||
+ (regs.eip != (unsigned long)&instr[3]) ||
+ (gs_base != 0x0000111122224444UL) ||
+ (gs_base_shadow != 0xffffeeeecccc8888UL) )
+ goto fail;
+ printf("okay\n");
+
+ printf("%-40s", "Testing lkgs 2(%rdx)...");
+ instr[0] = 0xf2; instr[1] = 0x0f; instr[2] = 0x00; instr[3] = 0x72;
instr[4] = 0x02;
+ regs.eip = (unsigned long)&instr[0];
+ regs.edx = (unsigned long)res;
+ res[0] = 0x00004444;
+ res[1] = 0x8888cccc;
+ i = cpu_policy.extd.nscb; cpu_policy.extd.nscb = true; /* for AMD */
+ rc = x86_emulate(&ctxt, &emulops);
+ if ( (rc != X86EMUL_OKAY) ||
+ (regs.eip != (unsigned long)&instr[5]) ||
+ (gs_base != 0x0000111122224444UL) ||
+ gs_base_shadow )
+ goto fail;
+
+ cpu_policy.extd.nscb = i;
+ emulops.write_segment = NULL;
+ emulops.write_msr = NULL;
#endif
printf("okay\n");
diff --git a/tools/tests/x86_emulator/x86-emulate.c
b/tools/tests/x86_emulator/x86-emulate.c
index 379e206dd3..b22c7d6add 100644
--- a/tools/tests/x86_emulator/x86-emulate.c
+++ b/tools/tests/x86_emulator/x86-emulate.c
@@ -85,6 +85,7 @@ bool emul_test_init(void)
cpu_policy.feat.invpcid = true;
cpu_policy.feat.adx = true;
cpu_policy.feat.rdpid = true;
+ cpu_policy.feat.lkgs = true;
cpu_policy.feat.wrmsrns = true;
cpu_policy.extd.clzero = true;
diff --git a/xen/arch/x86/x86_emulate/decode.c
b/xen/arch/x86/x86_emulate/decode.c
index 346777422b..2c13356c4d 100644
--- a/xen/arch/x86/x86_emulate/decode.c
+++ b/xen/arch/x86/x86_emulate/decode.c
@@ -745,8 +745,12 @@ decode_twobyte(struct x86_emulate_state *s,
case 0:
s->desc |= DstMem | SrcImplicit | Mov;
break;
+ case 6:
+ if ( !(s->modrm_reg & 1) && mode_64bit() )
+ {
case 2: case 4:
- s->desc |= SrcMem16;
+ s->desc |= SrcMem16;
+ }
break;
}
break;
diff --git a/xen/arch/x86/x86_emulate/private.h
b/xen/arch/x86/x86_emulate/private.h
index dfdc263f9c..6c96f72327 100644
--- a/xen/arch/x86/x86_emulate/private.h
+++ b/xen/arch/x86/x86_emulate/private.h
@@ -609,6 +609,7 @@ amd_like(const struct x86_emulate_ctxt *ctxt)
#define vcpu_has_avx_vnni() (ctxt->cpuid->feat.avx_vnni)
#define vcpu_has_avx512_bf16() (ctxt->cpuid->feat.avx512_bf16)
#define vcpu_has_cmpccxadd() (ctxt->cpuid->feat.cmpccxadd)
+#define vcpu_has_lkgs() (ctxt->cpuid->feat.lkgs)
#define vcpu_has_wrmsrns() (ctxt->cpuid->feat.wrmsrns)
#define vcpu_has_avx_ifma() (ctxt->cpuid->feat.avx_ifma)
#define vcpu_has_avx_vnni_int8() (ctxt->cpuid->feat.avx_vnni_int8)
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c
b/xen/arch/x86/x86_emulate/x86_emulate.c
index e58735ee95..364e6c092d 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -2899,8 +2899,37 @@ x86_emulate(
break;
}
break;
- default:
- generate_exception_if(true, X86_EXC_UD);
+
+ case 6: /* lkgs */
+ generate_exception_if((modrm_reg & 1) || vex.pfx != vex_f2,
+ X86_EXC_UD);
+ generate_exception_if(!mode_64bit() || !mode_ring0(), X86_EXC_UD);
+ vcpu_must_have(lkgs);
+ fail_if(!ops->read_msr || !ops->write_segment || !ops->write_msr);
+ if ( (rc = ops->read_msr(MSR_SHADOW_GS_BASE, &msr_val,
+ ctxt)) != X86EMUL_OKAY ||
+ (rc = ops->read_msr(MSR_GS_BASE, &sreg.base,
+ ctxt)) != X86EMUL_OKAY )
+ goto done;
+ dst.orig_val = sreg.base; /* Preserve current GS Base. */
+ if ( (rc = protmode_load_seg(x86_seg_gs, src.val, false, &sreg,
+ ctxt, ops)) != X86EMUL_OKAY )
+ goto done;
+ /* Write new base into SHADOW_GS, zero extended from GDT/LDT. */
+ if ( (rc = ops->write_msr(MSR_SHADOW_GS_BASE, sreg.base,
+ ctxt, false)) != X86EMUL_OKAY ||
+ (sreg.base = dst.orig_val, /* Reinstate original GS Base. */
+ (rc = ops->write_segment(x86_seg_gs, &sreg,
+ ctxt)) != X86EMUL_OKAY) )
+ {
+ /*
+ * In real hardware, access to the registers cannot fail. It
+ * is an error in Xen if the writes fail.
+ */
+ ASSERT_UNREACHABLE();
+ x86_emul_reset_event(ctxt);
+ generate_exception(X86_EXC_DF, 0);
+ }
break;
}
break;
diff --git a/xen/tools/gen-cpuid.py b/xen/tools/gen-cpuid.py
index b751dbab27..a30c68b40a 100755
--- a/xen/tools/gen-cpuid.py
+++ b/xen/tools/gen-cpuid.py
@@ -282,7 +282,8 @@ def crunch_numbers(state):
# superpages, PCID and PKU are only available in 4 level paging.
# NO_LMSL indicates the absense of Long Mode Segment Limits, which
# have been dropped in hardware.
- LM: [CX16, PCID, LAHF_LM, PAGE1GB, PKU, NO_LMSL, AMX_TILE, CMPCCXADD],
+ LM: [CX16, PCID, LAHF_LM, PAGE1GB, PKU, NO_LMSL, AMX_TILE, CMPCCXADD,
+ LKGS],
# AMD K6-2+ and K6-III processors shipped with 3DNow+, beyond the
# standard 3DNow in the earlier K6 processors.
--
generated by git-patchbot for /home/xen/git/xen.git#staging
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