From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 46A6B33CEB4 for ; Mon, 17 Nov 2025 17:03:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763399025; cv=none; b=YYREHxr2H6rcLor+dM5SZH1CHyzMpqfmzVOESPz5YJz7ayekSETKDFiUmDLog9JjjrT0YTvY6hDvFt2lN8FXdps8XXrgDrF1j35Yk80fm2KE7NRDOFAsiKgWnKwe82RK9crHZ7gairsgND4IPbCKeIobqcZUltgPua739IiXBhc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763399025; c=relaxed/simple; bh=bkVMcDwSIQqPy3ppwR3++s+E7Tde5RHH8Gep/ihy9i8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=pap21Aggjrvpmij08/NF9m+G8CmXmsg0uuOsazuWbYobSAW5SCZniWKFZ5nMX/5mrhIqNXOTOgvbsyhw/vdPVmV12Xa2KuxnyeMHFs0hc949hq9QtQX8QzrHVgYQAs9SFSBOPGr2nzyRhm8QMjPVqlL+s7FKg0vEpfkzX370Jjo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=rYpEo30R; arc=none smtp.client-ip=209.85.210.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="rYpEo30R" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-7b90740249dso9398775b3a.0 for ; Mon, 17 Nov 2025 09:03:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1763399023; x=1764003823; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=0hq6Uia9RhmITs3Fm5C1ux3TB78rTa2oGwDQ4IOSjBE=; b=rYpEo30RpXd7WtfTxTPw2DJWdaW4wEeNOB3FAF7M0R5noH4kkvp8HWqItfRFJOM9wq yDZxvZDGuh8yDkX30Qo/zsQGZWivVa9tNmS8Xnaa9Vdp6Pptcgm7+qJ9kCEBBpT8rH19 /Y9yS5gfQ/GwfSJZLV82KQuLlRekzS+3H4k2Y81rjV2YxFZPNXqHxvTNXczrS4ePzJhq DEX28q03BISuirAF9Osw5xq4/K0U7B2q7H4Jwb9lJJcig/PjoU4uXGnVvqMdazCtDmmt /g808ppriT3eD0opreVJZklP0gYh1Es5AGYv/o3cnbKx/hk99I4PZ3Ei+oFlUavCmLor FZEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1763399023; x=1764003823; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=0hq6Uia9RhmITs3Fm5C1ux3TB78rTa2oGwDQ4IOSjBE=; b=csi/n7tNPG8XRvuaWZx7K9tdChfoJlwHfIEQaYeYLoTzabnR0d9ZP3YnP3BjTLm9iG 9Dh/HQd6ggtidYYg7KRiG0EwJAFptUZPIoG9aImFPSCmyrz+HKuqVzrN1UGOiZLaqci2 lCMwA7U6qt1R8B5MqAYG6PBtTfoXS+bwsqIZfD8vSMHzfkdby1CoIHCDFbQnTCNWmw7w gguMtkZnyEFMCHNITRJ9cqy6UvI5Bxk/u9Ns/r/M2PFOR04Qy38hDCa0ynbQuh3Bz9GU duPB4sLBAmoXX3loXQg0bsoUYJoYmAOc3rm6KZvJfa4geSfuQ9+2LgIuXZVWjmagMKnB lP7g== X-Forwarded-Encrypted: i=1; AJvYcCVeMdkk4pm7JYkRUh0jIv1OYNZO0I3QN/BYaq631yH9W7MsQqlt5ZSDQToozf/FhDXERNDQvknv9RXCi7A=@vger.kernel.org X-Gm-Message-State: AOJu0YwIPGS7X1Cj5LM2toFYEgDyGyo7yDiEMstjQS6bRKHhGP04dFhV dh1SVGHf1Da33MAZYsCUQcfLSTQPKsHY8SVO0s9kDkekmGpyLnLRDM4ubseoG7Rcsj8c9Pn0TnD t0kRyMg== X-Google-Smtp-Source: AGHT+IGkp5EJaeics9rfr6OPoTNm9TOyUmNPfmPd5OleLPcrSezjyK79L0sxbr8BzPRbpMbixTLjg2AYM2E= X-Received: from pgnc22.prod.google.com ([2002:a63:7256:0:b0:bc3:7d57:2ea2]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:999f:b0:35e:7605:56a4 with SMTP id adf61e73a8af0-35e76055d0cmr7231438637.51.1763399023245; Mon, 17 Nov 2025 09:03:43 -0800 (PST) Date: Mon, 17 Nov 2025 09:03:41 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251112013017.1836863-1-yosry.ahmed@linux.dev> Message-ID: Subject: Re: [PATCH] KVM: SVM: Fix redundant updates of LBR MSR intercepts From: Sean Christopherson To: Yosry Ahmed Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Fri, Nov 14, 2025, Yosry Ahmed wrote: > On Fri, Nov 14, 2025 at 08:34:54AM -0800, Sean Christopherson wrote: > > On Wed, Nov 12, 2025, Yosry Ahmed wrote: > > > svm_update_lbrv() always updates LBR MSRs intercepts, even when they are > > > already set correctly. This results in force_msr_bitmap_recalc always > > > being set to true on every nested transition, > > > > Nit, it's only on VMRUN, not on every transition (i.e. not on nested #VMEXIT). > > How so? svm_update_lbrv() will also be called in nested_svm_vmexit(), > and it will eventually lead to force_msr_bitmap_recalc being set to > true. > > I guess what you meant is the "undoing the Hyper-V optimization" part. > That is indeed only affected by the svm_update_lbrv() call in the nested > VMRUN path. Ooh, yeah, my mind was fully on when the intercepts would be recomputed, not on when the flag could be set.