{"id":2196194,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2196194/?format=json","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/1.0/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260213034556.13471-11-mohamed@unpredictable.fr>","date":"2026-02-13T03:45:53","name":"[v2,10/10] whpx: x86: optimise MMIO vmexit by only restoring needed registers","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"8740479bc295587187c4861a81f9ee322bd3cc60","submitter":{"id":91318,"url":"http://patchwork.ozlabs.org/api/1.0/people/91318/?format=json","name":"Mohamed Mediouni","email":"mohamed@unpredictable.fr"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260213034556.13471-11-mohamed@unpredictable.fr/mbox/","series":[{"id":492055,"url":"http://patchwork.ozlabs.org/api/1.0/series/492055/?format=json","date":"2026-02-13T03:45:43","name":"whpx: x86 updates (2026-02)","version":2,"mbox":"http://patchwork.ozlabs.org/series/492055/mbox/"}],"check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2196194/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=unpredictable.fr header.i=@unpredictable.fr\n header.a=rsa-sha256 header.s=sig1 header.b=AR0AxXRO;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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helo=outbound.pv.icloud.com","X-Spam_score_int":"-20","X-Spam_score":"-2.1","X-Spam_bar":"--","X-Spam_report":"(-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1,\n DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001,\n RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001,\n SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no","X-Spam_action":"no action","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"Signed-off-by: Mohamed Mediouni \n---\n include/system/whpx-accel-ops.h | 8 +++++---\n target/i386/whpx/whpx-all.c | 12 ++++++++++--\n 2 files changed, 15 insertions(+), 5 deletions(-)","diff":"diff --git a/include/system/whpx-accel-ops.h b/include/system/whpx-accel-ops.h\nindex ed9d4c49f4..469a3a4350 100644\n--- a/include/system/whpx-accel-ops.h\n+++ b/include/system/whpx-accel-ops.h\n@@ -22,11 +22,13 @@ void whpx_cpu_synchronize_post_reset(CPUState *cpu);\n void whpx_cpu_synchronize_post_init(CPUState *cpu);\n void whpx_cpu_synchronize_pre_loadvm(CPUState *cpu);\n \n+/* subset of runtime state for faster returns from vmexit */\n+#define WHPX_SET_FAST_RUNTIME_STATE 1\n /* state subset only touched by the VCPU itself during runtime */\n-#define WHPX_SET_RUNTIME_STATE 1\n+#define WHPX_SET_RUNTIME_STATE 2\n /* state subset modified during VCPU reset */\n-#define WHPX_SET_RESET_STATE 2\n+#define WHPX_SET_RESET_STATE 3\n /* full state set, modified during initialization or on vmload */\n-#define WHPX_SET_FULL_STATE 3\n+#define WHPX_SET_FULL_STATE 4\n \n #endif /* TARGET_I386_WHPX_ACCEL_OPS_H */\ndiff --git a/target/i386/whpx/whpx-all.c b/target/i386/whpx/whpx-all.c\nindex 0e8fb0e72e..61251a2835 100644\n--- a/target/i386/whpx/whpx-all.c\n+++ b/target/i386/whpx/whpx-all.c\n@@ -420,6 +420,13 @@ void whpx_set_registers(CPUState *cpu, int level)\n vcxt.values[idx].Segment = whpx_seg_q2h(&env->segs[i], v86, r86);\n }\n \n+ /*\n+ * This is a hot path called on every MMIO access.\n+ */\n+ if (level <= WHPX_SET_FAST_RUNTIME_STATE) {\n+ goto skip_to_set_registers;\n+ }\n+\n assert(idx == WHvX64RegisterLdtr);\n vcxt.values[idx++].Segment = whpx_seg_q2h(&env->ldt, 0, 0);\n \n@@ -529,10 +536,11 @@ void whpx_set_registers(CPUState *cpu, int level)\n \n assert(idx == RTL_NUMBER_OF(whpx_register_names));\n \n+ skip_to_set_registers:\n hr = whp_dispatch.WHvSetVirtualProcessorRegisters(\n whpx->partition, cpu->cpu_index,\n whpx_register_names,\n- RTL_NUMBER_OF(whpx_register_names),\n+ idx,\n &vcxt.values[0]);\n \n if (FAILED(hr)) {\n@@ -771,7 +779,7 @@ static int emulate_instruction(CPUState *cpu, const uint8_t *insn_bytes, size_t\n whpx_get_registers(cpu);\n decode_instruction_stream(env, &decode, &stream);\n exec_instruction(env, &decode);\n- whpx_set_registers(cpu, WHPX_SET_RUNTIME_STATE);\n+ whpx_set_registers(cpu, WHPX_SET_FAST_RUNTIME_STATE);\n \n return 0;\n }\n","prefixes":["v2","10/10"]}