Re: AMD DC graphics display code enables -mhard-float, -msse, -msse2 without any visible FPU state protection

From: Peter Zijlstra <peterz@infradead.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: "Christian König" <christian.koenig@amd.com>,
	"Jann Horn" <jannh@google.com>,
	"Harry Wentland" <harry.wentland@amd.com>,
	"Leo Li" <sunpeng.li@amd.com>,
	amd-gfx@lists.freedesktop.org,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"David (ChunMing) Zhou" <David1.Zhou@amd.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	"kernel list" <linux-kernel@vger.kernel.org>,
	"Josh Poimboeuf" <jpoimboe@redhat.com>,
	"Andy Lutomirski" <luto@kernel.org>,
	"Arnaldo Carvalho de Melo" <acme@kernel.org>
Subject: Re: AMD DC graphics display code enables -mhard-float, -msse, -msse2 without any visible FPU state protection
Date: Tue, 7 Apr 2020 17:54:49 +0200	[thread overview]
Message-ID: <20200407155449.GF20730@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200408004111.3dd597f2a7c6172b4c71a9ba@kernel.org>

On Wed, Apr 08, 2020 at 12:41:11AM +0900, Masami Hiramatsu wrote:
> On Tue, 7 Apr 2020 13:15:35 +0200
> Peter Zijlstra <peterz@infradead.org> wrote:

> > > > Also, all the VMX bits seems to qualify as FPU (I can't remember seeing
> > > > that previously):
> > > 
> > > Oops, let me check it.
> > 
> > I just send you another patch that could do with insn_is_vmx()
> > (sorry!!!)
> 
> Hmm, it is hard to find out the vmx insns. Maybe we need to clarify it by
> opcode pattern. (like "VM.*")

Yeah, I know. Maybe I should just keep it as I have for now.

One thing I thought of is we could perhaps add manual markers in
x86-opcode-map.txt. The '{','}' characters appear unused so far, we
perhaps we can use them to classify things.

That could maybe replace "mmx_expr" as well. That is, something like so:

---

diff --git a/arch/x86/lib/x86-opcode-map.txt b/arch/x86/lib/x86-opcode-map.txt
index ec31f5b60323..e01b76e0a294 100644
--- a/arch/x86/lib/x86-opcode-map.txt
+++ b/arch/x86/lib/x86-opcode-map.txt
@@ -462,9 +462,9 @@ AVXcode: 1
 75: pcmpeqw Pq,Qq | vpcmpeqw Vx,Hx,Wx (66),(v1)
 76: pcmpeqd Pq,Qq | vpcmpeqd Vx,Hx,Wx (66),(v1)
 # Note: Remove (v), because vzeroall and vzeroupper becomes emms without VEX.
-77: emms | vzeroupper | vzeroall
-78: VMREAD Ey,Gy | vcvttps2udq/pd2udq Vx,Wpd (evo) | vcvttsd2usi Gv,Wx (F2),(ev) | vcvttss2usi Gv,Wx (F3),(ev) | vcvttps2uqq/pd2uqq Vx,Wx (66),(ev)
-79: VMWRITE Gy,Ey | vcvtps2udq/pd2udq Vx,Wpd (evo) | vcvtsd2usi Gv,Wx (F2),(ev) | vcvtss2usi Gv,Wx (F3),(ev) | vcvtps2uqq/pd2uqq Vx,Wx (66),(ev)
+77: emms {FPU} | vzeroupper | vzeroall
+78: VMREAD Ey,Gy {VMX} | vcvttps2udq/pd2udq Vx,Wpd (evo) | vcvttsd2usi Gv,Wx (F2),(ev) | vcvttss2usi Gv,Wx (F3),(ev) | vcvttps2uqq/pd2uqq Vx,Wx (66),(ev)
+79: VMWRITE Gy,Ey {VMX} | vcvtps2udq/pd2udq Vx,Wpd (evo) | vcvtsd2usi Gv,Wx (F2),(ev) | vcvtss2usi Gv,Wx (F3),(ev) | vcvtps2uqq/pd2uqq Vx,Wx (66),(ev)
 7a: vcvtudq2pd/uqq2pd Vpd,Wx (F3),(ev) | vcvtudq2ps/uqq2ps Vpd,Wx (F2),(ev) | vcvttps2qq/pd2qq Vx,Wx (66),(ev)
 7b: vcvtusi2sd Vpd,Hpd,Ev (F2),(ev) | vcvtusi2ss Vps,Hps,Ev (F3),(ev) | vcvtps2qq/pd2qq Vx,Wx (66),(ev)
 7c: vhaddpd Vpd,Hpd,Wpd (66) | vhaddps Vps,Hps,Wps (F2)
@@ -965,9 +965,9 @@ GrpTable: Grp6
 EndTable
 
 GrpTable: Grp7
-0: SGDT Ms | VMCALL (001),(11B) | VMLAUNCH (010),(11B) | VMRESUME (011),(11B) | VMXOFF (100),(11B) | PCONFIG (101),(11B) | ENCLV (000),(11B)
+0: SGDT Ms | VMCALL (001),(11B) {VMX} | VMLAUNCH (010),(11B) {VMX} | VMRESUME (011),(11B) {VMX} | VMXOFF (100),(11B) {VMX} | PCONFIG (101),(11B) | ENCLV (000),(11B)
 1: SIDT Ms | MONITOR (000),(11B) | MWAIT (001),(11B) | CLAC (010),(11B) | STAC (011),(11B) | ENCLS (111),(11B)
-2: LGDT Ms | XGETBV (000),(11B) | XSETBV (001),(11B) | VMFUNC (100),(11B) | XEND (101)(11B) | XTEST (110)(11B) | ENCLU (111),(11B)
+2: LGDT Ms | XGETBV (000),(11B) | XSETBV (001),(11B) | VMFUNC (100),(11B) {VMX} | XEND (101)(11B) | XTEST (110)(11B) | ENCLU (111),(11B)
 3: LIDT Ms
 4: SMSW Mw/Rv
 5: rdpkru (110),(11B) | wrpkru (111),(11B) | SAVEPREVSSP (F3),(010),(11B) | RSTORSSP Mq (F3) | SETSSBSY (F3),(000),(11B)
@@ -987,8 +987,8 @@ GrpTable: Grp9
 3: xrstors
 4: xsavec
 5: xsaves
-6: VMPTRLD Mq | VMCLEAR Mq (66) | VMXON Mq (F3) | RDRAND Rv (11B)
-7: VMPTRST Mq | VMPTRST Mq (F3) | RDSEED Rv (11B)
+6: VMPTRLD Mq {VMX} | VMCLEAR Mq (66) {VMX} | VMXON Mq (F3) {VMX} | RDRAND Rv (11B)
+7: VMPTRST Mq {VMX} | VMPTRST Mq (F3) {VMX} | RDSEED Rv (11B)
 EndTable
 
 GrpTable: Grp10
@@ -1036,10 +1036,10 @@ GrpTable: Grp14
 EndTable
 
 GrpTable: Grp15
-0: fxsave | RDFSBASE Ry (F3),(11B)
-1: fxstor | RDGSBASE Ry (F3),(11B)
-2: vldmxcsr Md (v1) | WRFSBASE Ry (F3),(11B)
-3: vstmxcsr Md (v1) | WRGSBASE Ry (F3),(11B)
+0: fxsave {FPU} | RDFSBASE Ry (F3),(11B)
+1: fxrstor {FPU} | RDGSBASE Ry (F3),(11B)
+2: ldmxcsr {FPU} | vldmxcsr Md (v1) | WRFSBASE Ry (F3),(11B)
+3: stmxcsr {FPU} | vstmxcsr Md (v1) | WRGSBASE Ry (F3),(11B)
 4: XSAVE | ptwrite Ey (F3),(11B)
 5: XRSTOR | lfence (11B) | INCSSPD/Q Ry (F3),(11B)
 6: XSAVEOPT | clwb (66) | mfence (11B) | TPAUSE Rd (66),(11B) | UMONITOR Rv (F3),(11B) | UMWAIT Rd (F2),(11B) | CLRSSBSY Mq (F3)
