From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AA3952586E7 for ; Wed, 26 Mar 2025 19:45:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743018311; cv=none; b=PRCX9Olw6+oscNCLi5rUlBUAEHogI+4FAAep/Ac+8ClnwGZTyaEUkEdGNRLG8W2tXX4MG2ZEVvURgT3lAD6CXbYsffOORSjZwL4t2JeG3mO590D2Oxt3VSFZChqbLvBuqrfBtf4OXQ3WUDE0JH8+0UVWQCLPUYib4m5aSSAP64k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743018311; c=relaxed/simple; bh=3K6yLvIkonK1mZsFWuMCKFfVT/bOP7TUxS9pNzKsNJE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dyplXxxXJzmvGqF95oANVEakZX03ag3tqmiLhLnJJjekjsMFgxKLDNalC3KTTirnOGyz71zRlD6qPrNsUxLAq8GowxoTjsLL7rFc/Ko34dpwgNsXjBIsRz2yvrwKJL3zNoK9EZi3hduNXXqxXCcxJteXlXyyh7VUxleRkksaGZc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=qfumM5F3; arc=none smtp.client-ip=95.215.58.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="qfumM5F3" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1743018307; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nzFYYv0ZerKKI50mE9D2vjgjMS3N0gQVxT4sNZcZOPU=; b=qfumM5F3ZtYhcofwQ2T6BQtxf+Bg7cW7WKkbv8V1zhV92yxPgvapRxUg1opVFnawIXF95r 3asdpPvjvFWvjDF4qDDcNoz3BGmOIqej95SlSxfqvWNXIqmbKzs7VfXBEobLIwJ3Iv4u1T YIo3l/8lXAzAyH10dRqWv6m12PZ5Nr4= From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , Jim Mattson , Maxim Levitsky , Vitaly Kuznetsov , Rik van Riel , Tom Lendacky , x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yosry Ahmed Subject: [RFC PATCH 24/24] KVM: nSVM: Stop bombing the TLB on nested transitions Date: Wed, 26 Mar 2025 19:44:23 +0000 Message-ID: <20250326194423.3717668-5-yosry.ahmed@linux.dev> In-Reply-To: <20250326194423.3717668-1-yosry.ahmed@linux.dev> References: <20250326193619.3714986-1-yosry.ahmed@linux.dev> <20250326194423.3717668-1-yosry.ahmed@linux.dev> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Now that nested TLB flushes are properly tracked with a well-maintained separate ASID for L2 and proper handling of L1's TLB flush requests, drop the unconditional flushes and syncs on nested transitions. On a Milan machine, an L1 and L2 guests were booted, both with a single vCPU, and pinned to a single physical CPU to maximize TLB collisions. In this setup, the cpuid_rate microbenchmark [1] showed the following changes with this patch: +--------+--------+-------------------+----------------------+ | L0 | L1 | cpuid_rate (base) | cpuid_rate (patched) | +========+========+===================+======================+ | NPT | NPT | 256621 | 301113 (+17.3%) | | NPT | Shadow | 180017 | 203347 (+12.96%) | | Shadow | Shadow | 177006 | 189150 (+6.86%) | +--------+--------+-------------------+----------------------+ [1]https://lore.kernel.org/kvm/20231109180646.2963718-1-khorenko@virtuozzo.com/ Reviewed-by: Maxim Levitsky Signed-off-by: Yosry Ahmed --- arch/x86/kvm/svm/nested.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 0c887c91bd50d..1cc281a7b666c 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -511,9 +511,6 @@ static void nested_svm_entry_tlb_flush(struct kvm_vcpu *vcpu) svm->nested.last_asid = svm->nested.ctl.asid; kvm_make_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu); } - /* TODO: optimize unconditional TLB flush/MMU sync */ - kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); } /* See nested_svm_entry_tlb_flush() */ @@ -525,9 +522,6 @@ static void nested_svm_exit_tlb_flush(struct kvm_vcpu *vcpu) if (svm->nested.ctl.tlb_ctl == TLB_CONTROL_FLUSH_ALL_ASID) kvm_make_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu); - - kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); } /* -- 2.49.0.395.g12beb8f557-goog