[xen stable-4.18] x86emul: add missing EVEX.R' checks

[patchbot@xxxxxxx]

commit a751d1321f6e1491d6ec2134d59eefa9f9752b86
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Feb 27 13:57:50 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Feb 27 13:57:50 2024 +0100

    x86emul: add missing EVEX.R' checks
    
    EVEX.R' is not ignored in 64-bit code when encoding a GPR or mask
    register. While for mask registers suitable checks are in place (there
    also covering EVEX.R), they were missing for the few cases where in
    EVEX-encoded instructions ModR/M.reg encodes a GPR. While for VPEXTRW
    the bit is replaced before an emulation stub is invoked, for
    VCVT{,T}{S,D,H}2{,U}SI this actually would have led to #UD from inside
    an emulation stub, in turn raising #UD to the guest, but accompanied by
    log messages indicating something's wrong in Xen nevertheless.
    
    Fixes: 001bd91ad864 ("x86emul: support AVX512{F,BW,DQ} extract insns")
    Fixes: baf4a376f550 ("x86emul: support AVX512F legacy-equivalent scalar 
int/FP conversion insns")
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: cb319824bfa8d3c9ea0410cc71daaedc3e11aa2a
    master date: 2024-02-22 11:54:07 +0100
---
 xen/arch/x86/x86_emulate/x86_emulate.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index cf780da501..d6b60f0539 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -3686,7 +3686,8 @@ x86_emulate(
     CASE_SIMD_SCALAR_FP(_EVEX, 0x0f, 0x2d): /* vcvts{s,d}2si xmm/mem,reg */
     CASE_SIMD_SCALAR_FP(_EVEX, 0x0f, 0x78): /* vcvtts{s,d}2usi xmm/mem,reg */
     CASE_SIMD_SCALAR_FP(_EVEX, 0x0f, 0x79): /* vcvts{s,d}2usi xmm/mem,reg */
-        generate_exception_if((evex.reg != 0xf || !evex.RX || evex.opmsk ||
+        generate_exception_if((evex.reg != 0xf || !evex.RX || !evex.R ||
+                               evex.opmsk ||
                                (ea.type != OP_REG && evex.brs)),
                               X86_EXC_UD);
         host_and_vcpu_must_have(avx512f);
@@ -7295,7 +7296,7 @@ x86_emulate(
         goto pextr;
 
     case X86EMUL_OPC_EVEX_66(0x0f, 0xc5):   /* vpextrw $imm8,xmm,reg */
-        generate_exception_if(ea.type != OP_REG, X86_EXC_UD);
+        generate_exception_if(ea.type != OP_REG || !evex.R, X86_EXC_UD);
         /* Convert to alternative encoding: We want to use a memory operand. */
         evex.opcx = ext_0f3a;
         b = 0x15;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.18