Re: [PATCH] i386/hvf: Integrates x2APIC support with hvf accel

[Phil Dennis-Jordan]

Pinging Philippe and Akihiko-san. Would you mind taking a look at this patch as you've tested & reviewed other macOS specific patches? We've found it to improve performance by 20%+ on most SMP guest workloads. The listed HVF maintainers haven't been active on-list for 8+ months, so unless patches touch code areas with other maintainers, HVF patches are mostly being ignored.

Thanks!

Phil

On Mon, 8 Jul 2024 at 16:37, Phil Dennis-Jordan <phil@philjordan.eu> wrote:

Ping!

It would be nice to get this one in before the 9.1 merge window closes.

Thanks,

Phil

On Mon, 24 Jun 2024 at 11:47, Phil Dennis-Jordan <phil@philjordan.eu> wrote:

Support for x2APIC mode was recently introduced in the software emulated
APIC implementation for TCG. Enabling it when using macOS’s hvf
accelerator is useful and significantly helps performance, as Qemu
currently uses the emulated APIC when running on hvf as well.

This change wires up the read & write operations for the MSR VM exits
and allow-lists the CPUID flag in the x86 hvf runtime.

Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>
---
 target/i386/hvf/x86_cpuid.c |  4 ++--
 target/i386/hvf/x86_emu.c   | 31 +++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/target/i386/hvf/x86_cpuid.c b/target/i386/hvf/x86_cpuid.c
index e56cd8411b..4f260d46a8 100644
--- a/target/i386/hvf/x86_cpuid.c
+++ b/target/i386/hvf/x86_cpuid.c
@@ -64,8 +64,8 @@ uint32_t hvf_get_supported_cpuid(uint32_t func, uint32_t idx,
              CPUID_PAT | CPUID_PSE36 | CPUID_CLFLUSH | CPUID_MMX |
              CPUID_FXSR | CPUID_SSE | CPUID_SSE2 | CPUID_SS;
         ecx &= CPUID_EXT_SSE3 | CPUID_EXT_PCLMULQDQ | CPUID_EXT_SSSE3 |
-             CPUID_EXT_FMA | CPUID_EXT_CX16 | CPUID_EXT_PCID |
-             CPUID_EXT_SSE41 | CPUID_EXT_SSE42 | CPUID_EXT_MOVBE |
+             CPUID_EXT_FMA | CPUID_EXT_CX16 | CPUID_EXT_PCID | CPUID_EXT_SSE41 |
+             CPUID_EXT_SSE42 | CPUID_EXT_X2APIC | CPUID_EXT_MOVBE |
              CPUID_EXT_POPCNT | CPUID_EXT_AES | CPUID_EXT_XSAVE |
              CPUID_EXT_AVX | CPUID_EXT_F16C | CPUID_EXT_RDRAND;
         ecx |= CPUID_EXT_HYPERVISOR;
diff --git a/target/i386/hvf/x86_emu.c b/target/i386/hvf/x86_emu.c
index 38c782b8e3..be675bcfb7 100644
--- a/target/i386/hvf/x86_emu.c
+++ b/target/i386/hvf/x86_emu.c
@@ -663,6 +663,15 @@ static void exec_lods(CPUX86State *env, struct x86_decode *decode)
     env->eip += decode->len;
 }

+static void raise_exception(CPUX86State *env, int exception_index,
+                            int error_code)
+{
+    env->exception_nr = exception_index;
+    env->error_code = error_code;
+    env->has_error_code = true;
+    env->exception_injected = 1;
+}
+
 void simulate_rdmsr(CPUX86State *env)
 {
     X86CPU *cpu = env_archcpu(env);
@@ -677,6 +686,17 @@ void simulate_rdmsr(CPUX86State *env)
     case MSR_IA32_APICBASE:
         val = cpu_get_apic_base(cpu->apic_state);
         break;
+    case MSR_APIC_START ... MSR_APIC_END: {
+        int ret;
+        int index = (uint32_t)env->regs[R_ECX] - MSR_APIC_START;
+
+        ret = apic_msr_read(index, &val);
+        if (ret < 0) {
+            raise_exception(env, EXCP0D_GPF, 0);
+        }
+
+        break;
+    }
     case MSR_IA32_UCODE_REV:
         val = cpu->ucode_rev;
         break;
@@ -777,6 +797,17 @@ void simulate_wrmsr(CPUX86State *env)
     case MSR_IA32_APICBASE:
         cpu_set_apic_base(cpu->apic_state, data);
         break;
+    case MSR_APIC_START ... MSR_APIC_END: {
+        int ret;
+        int index = (uint32_t)env->regs[R_ECX] - MSR_APIC_START;
+
+        ret = apic_msr_write(index, data);
+        if (ret < 0) {
+            raise_exception(env, EXCP0D_GPF, 0);
+        }
+
+        break;
+    }
     case MSR_FSBASE:
         wvmcs(cs->accel->fd, VMCS_GUEST_FS_BASE, data);
         break;
--
2.39.3 (Apple Git-146)