Update AMD instructions to conform to LLVM assembler

PATCH Applied Jim Mattson 3 participants 4 messages Dec 11, 2019 – Dec 18, 2019 1 message not in the archive KVM

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A message that is not in the archive (sent off-list or not yet received): [email protected]

Paolo Bonzini

maintainer

2019-12-12 00:40 UTC #2 lore raw

Quoted 75 lines · Jim Mattson

Quoted 74 lines · Peter Shier

The GNU assembler (gas) allows omitting operands where there is only a single choice e.g. "VMRUN rAX".The LLVM assembler requires those operands even though they are the default and only choice.

In addition, LLVM does not allow a CLGI instruction with a terminating \n\t. Adding a ; separator after the instruction is a workaround.

Signed-off-by Peter Shier <[email protected]>

Reviewed-by Marc Orr <[email protected]>

Reviewed-by Jim Mattson <[email protected]>

---
 x86/svm.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

x86/svm.c +7 -7

index bc74e7c690a8..e5cb730b08cb 100644
@@ -154,7 +154,7 @@ static void vmcb_ident(struct vmcb *vmcb)
     struct descriptor_table_ptr desc_table_ptr;
 
     memset(vmcb, 0, sizeof(*vmcb));
-    asm volatile ("vmsave" : : "a"(vmcb_phys) : "memory");
+    asm volatile ("vmsave %0" : : "a"(vmcb_phys) : "memory");
     vmcb_set_seg(&save->es, read_es(), 0, -1U, data_seg_attr);
     vmcb_set_seg(&save->cs, read_cs(), 0, -1U, code_seg_attr);
     vmcb_set_seg(&save->ss, read_ss(), 0, -1U, data_seg_attr);

@@ -262,20 +262,20 @@ static void test_run(struct test *test, struct vmcb *vmcb)
     do {
         tsc_start = rdtsc();
         asm volatile (
-            "clgi \n\t"
-            "vmload \n\t"
+            "clgi;\n\t" // semi-colon needed for LLVM compatibility
+            "vmload %0\n\t"
             "mov regs+0x80, %%r15\n\t"  // rflags
             "mov %%r15, 0x170(%0)\n\t"
             "mov regs, %%r15\n\t"       // rax
             "mov %%r15, 0x1f8(%0)\n\t"
             LOAD_GPR_C
-            "vmrun \n\t"
+            "vmrun %0\n\t"
             SAVE_GPR_C
             "mov 0x170(%0), %%r15\n\t"  // rflags
             "mov %%r15, regs+0x80\n\t"
             "mov 0x1f8(%0), %%r15\n\t"  // rax
             "mov %%r15, regs\n\t"
-            "vmsave \n\t"
+            "vmsave %0\n\t"
             "stgi"
             : : "a"(vmcb_phys)
             : "rbx", "rcx", "rdx", "rsi",

@@ -330,7 +330,7 @@ static bool check_no_vmrun_int(struct test *test)
 
 static void test_vmrun(struct test *test)
 {
-    asm volatile ("vmrun" : : "a"(virt_to_phys(test->vmcb)));
+    asm volatile ("vmrun %0" : : "a"(virt_to_phys(test->vmcb)));
 }
 
 static bool check_vmrun(struct test *test)

@@ -1241,7 +1241,7 @@ static bool lat_svm_insn_finished(struct test *test)
 
     for ( ; runs != 0; runs--) {
         tsc_start = rdtsc();
-        asm volatile("vmload\n\t" : : "a"(vmcb_phys) : "memory");
+        asm volatile("vmload %0\n\t" : : "a"(vmcb_phys) : "memory");
         cycles = rdtsc() - tsc_start;
         if (cycles > latvmload_max)
             latvmload_max = cycles;

@@ -1250,7 +1250,7 @@ static bool lat_svm_insn_finished(struct test *test)
         vmload_sum += cycles;

Quoted 9 lines

x86/svm.c static bool lat_svm_insn_finished(struct test *test) · line 1256

Quoted 6 lines

x86/svm.c +1 -1

         tsc_start = rdtsc();
-        asm volatile("vmsave\n\t" : : "a"(vmcb_phys) : "memory");
+        asm volatile("vmsave %0\n\t" : : "a"(vmcb_phys) : "memory");
         cycles = rdtsc() - tsc_start;
         if (cycles > latvmsave_max)
             latvmsave_max = cycles;

Ping.

I am applying it, but I'm seriously puzzled by the clgi one. Can you open a bug on LLVM?

Paolo

Fangrui Song

2019-12-14 19:10 UTC #4 lore raw

In reply to a message not in the archive

Quoted 4 lines

I am applying it, but I'm seriously puzzled by the clgi one. Can you open a bug on LLVM?
Paolo

The clgi change does not appear to be needed.

- "clgi \n\t"
+ "clgi;\n\t"

clang 7.0.0, 8.0.0 (downloaded from releases.llvm.org) and HEAD (built from source) compile "clgi" fine.

% ~/ccls/build/clang+llvm-7.0.0-x86_64-linux-gnu-ubuntu-16.04/bin/clang -mno-red-zone -mno-sse -mno-sse2 -m64 -O1 -g -MMD -MF x86/.emulator.d -Wall -Wwrite-strings -Wempty-body -Wuninitialized -Wignored-qualifiers -fno-omit-frame-pointer -fno-pic -Woverride-init -Wmissing-prototypes -Wstrict-prototypes -std=gnu99 -ffreestanding -I /tmp/p/kvm-unit-tests/lib -I /tmp/p/kvm-unit-tests/lib/x86 -I lib -c -o x86/svm.o x86/svm.c -w

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