From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A4548C98321 for ; Fri, 25 Sep 2026 15:02:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=uQbHVyvOfJT59Z1tjcStlzFu/GfhyqjlrHuEPmE7uTg=; b=K5duBEdBNdRTS/kwOuecqcu3+D jtDd0fyaXY6FXBBdtSA+9yrfR/V1ZgmSkVbEtDMc2QC+vxmSPO1SpXjtwkXhWe6XzO3UBZXd+gli9 HcExEkkzvaDdRpg4cQeREqbBvn9vn4rOIph3ueJdsP5JwvBtAFb+EOjMrR2fq4eIlIbN0YKei0T9e pQUmBi1gydGPHQf0SdlWt1M1wb4i9TfyrzBgJShCHx0uJBu+gboJtQ2sa7UM92N2jalbIXj8ZoLx7 ATioa6WVplQSxqLdNk9tPGQKF079opKUiK85nTnGT1bwjwtJ9dB2yun4IQDJX0ESFfNhXJgreHnU1 L6r/31RQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xA7Rh-0000000DgUa-0fNO; Fri, 25 Sep 2026 15:02:41 +0000 Received: from mail-wm2-x11.google.com ([2a00:1450:4864:31::11]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xA7Rd-0000000DgSN-3C1t for linux-arm-kernel@lists.infradead.org; Fri, 25 Sep 2026 15:02:39 +0000 Received: by mail-wm2-x11.google.com with SMTP id 5b1f17b1804b1-49e71cdb22bso7505295e9.2 for ; Fri, 25 Sep 2026 08:02:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1790348555; x=1790953355; darn=lists.infradead.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=uQbHVyvOfJT59Z1tjcStlzFu/GfhyqjlrHuEPmE7uTg=; b=b2fNHSRA3cBhEIW5JOcETXcXdhc21J5fvSziZ3XZ5VvxDaV/Wwwf8KqJqin3yr0mD7 We37pESNZv12Wcsyn8joi8sJ8hi6azyCjXCQ4OwWM6FPv1WC1iXUTqpkGSnm4bNFlUz1 FhMnmtu2YpYsdwIttn4fSk/mUWPZnK3S7Wp1XNulkG09p3kakeuhdBsJh0Nn7W0PAUUT ZRDU05dvX6aperun7mj78tcCzoHqRYv0wDhbi08olCvrUoCv4IevySwa9FNJqTbRML1v qSWTLIpAXOqg0hjzpOAuXZEzIezRfFX6Rh/90F1hiS2Wdls/z7JDKnVGGzVefrQ9quem rxUg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790348555; x=1790953355; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=uQbHVyvOfJT59Z1tjcStlzFu/GfhyqjlrHuEPmE7uTg=; b=DSNWeY6esdUrEkcT729TOzIo/POQcMO6APavMYbooSs7/ksg8aLlduXpKH9ySdusMa mU/ox3BnNimDynbUhbsREYSTQdPe0oXNNfj6M/z44HJU4YM8fDUKDWShCysTw6K15Vzj l9i2bgxgtuGgbgsEFgObIpaSa1OAbccljOX3fPZELsUAlucloSr9O00LWNr7jKWhX8ZZ 8Fj6QfuZ1kpKlP7DlV3KSpSuHgzSjVKI/h32rJGpqAA1oOJxkUaqg1vMgcHmXYhuloiv VCgYKGn/MZ2leFTB/JsoC1PiwXiJiO5g66XeSjBL2YZ1xt+xb0i6TgW1LeIz7YMHrSN9 5s/Q== X-Forwarded-Encrypted: i=1; AKwUvBzMGG2EM8Kc7hJV9MNe4THbfbnutqVNozBh1/9LPje3WY4aLEdaAwzxDA/Z+uzB4f1ElWHc7RJ80RPpHH6G4tiy@lists.infradead.org X-Gm-Message-State: AFuF++m588vSt+0D4GPu1/9QOgRHWz7iLp2lGDLc2e45uehx458ed2i9 yLOe/P/8ZjVls9QMudARfoh3k3FaxEEvf2H4htVc1eiw9dXymSSotQWffQDubv4YYg== X-Gm-Gg: AYBFou3IQD39lKa0gSbO3BlBCwrOhsQDedOrgJyJwXREGheF7YzqoyXBkFAB9M6dMAC u/Ev9FkyLkKpvP4Hp7qihL8LyoMkP5n1fnJDcztJrg3h5GwU5qhHwV6WoNV+/iir4oTaOm5oiD2 GSwWaz9NCObxQDMGdQ1LBYgRYfr75NzQwQ2BWz2bZTFr1wUaRjx0VJsY69fucYk3ROSLt1VBr9J Ze4rtkC0DFXmlfd/j/dYMzTWPf6K3U5hJFZbdxdwYj7TJjFSENSvG0fuvIzBRBH9vR5vGr+jKJ5 R2m0ZmqcmHgJ/hNcBlZjnlQTw44Suc0fL+4bCv7fZva48LH8++TpSqAvb/CHGrxyjLh8/53VtSc MhDFkhb7RcK0fVykq+lKx5ekYLUKwNVYpjr8J9bf3HJzHYlqNlALoW0dmx2ewgzL+kOeOkUzZYv R0RnAwQ1MJYIxVIcsa+8ItVNWVPgRDzW9Y8b0JyyEVNpkf492d2DpUvnfid9gMc4iYTqlgdfakk eVShdszZBeZoszx4lms3L7/qT23T4xTR1BJUHCPFjY= X-Received: by 2002:a05:600c:4594:b0:49e:6249:268b with SMTP id 5b1f17b1804b1-49fe6707f69mr117966225e9.32.1790348554298; Fri, 25 Sep 2026 08:02:34 -0700 (PDT) Received: from google.com (135.91.155.104.bc.googleusercontent.com. [104.155.91.135]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49ff06bdef2sm66540075e9.11.2026.09.25.08.02.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Sep 2026 08:02:31 -0700 (PDT) Date: Fri, 25 Sep 2026 16:02:27 +0100 From: Vincent Donnefort To: Mostafa Saleh Cc: maz@kernel.org, oupton@kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, kernel-team@android.com, fuad.tabba@linux.dev, qperret@google.com, weilin.chang@arm.com, Keir Fraser Subject: Re: [PATCH v2 01/22] KVM: arm64: Prefault host stage-2 entries on block split Message-ID: References: <20260911135053.146435-1-vdonnefort@google.com> <20260911135053.146435-2-vdonnefort@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260925_080237_858874_E84ADEF9 X-CRM114-Status: GOOD ( 34.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Sep 24, 2026 at 05:38:49PM +0000, Mostafa Saleh wrote: > On Fri, Sep 11, 2026 at 02:50:32PM +0100, 'Vincent Donnefort' via kernel-team wrote: > > From: Keir Fraser > > > > For the host stage-2 that is idmap, we can avoid lazy-mapping on block > > splitting by propagating existing valid mappings to neighbouring entries > > of the new table. > > > > Signed-off-by: Keir Fraser > > Co-developed-by: Quentin Perret > > Signed-off-by: Quentin Perret > > Signed-off-by: Vincent Donnefort > > --- > > arch/arm64/kvm/hyp/pgtable.c | 32 ++++++++++++++++++++++++++++++++ > > 1 file changed, 32 insertions(+) > > > > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > > index b74dd5ce1efd..34f78a58cded 100644 > > --- a/arch/arm64/kvm/hyp/pgtable.c > > +++ b/arch/arm64/kvm/hyp/pgtable.c > > @@ -1030,10 +1030,39 @@ static int stage2_map_walk_table_pre(const struct kvm_pgtable_visit_ctx *ctx, > > return 0; > > } > > > > +static void stage2_map_prefault_idmap(const struct kvm_pgtable_visit_ctx *ctx, kvm_pte_t *ptep) > > +{ > > + kvm_pte_t block_pte = ctx->old; > > + u64 pa; > > + int i; > > + > > + if (!kvm_pte_valid(block_pte)) > > + return; > > + > > + pa = ALIGN_DOWN(ctx->addr, kvm_granule_size(ctx->level)); > > + for (i = 0; i < PTRS_PER_PTE; ++i, ++ptep, pa += kvm_granule_size(ctx->level + 1)) { > > + kvm_pte_t pte = kvm_init_valid_leaf_pte(pa, block_pte, ctx->level + 1); > > + > > + /* > > + * Skip ptes in the range being modified by the caller if we're > > + * installing last level entries. Otherwise, we need to > > + * temporarily put in a valid mapping to make sure the > > + * prefaulting logic is triggered on the next > > + * stage2_map_walk_leaf(). This adds an unnecessary TLBI as > > + * we'll presumably re-break the freshly installed block, but > > + * that should happen very infrequently. > > + */ > > + if ((ctx->level < (KVM_PGTABLE_LAST_LEVEL - 1)) || > > + (pa < ctx->addr) || (pa >= ctx->end)) > > + *ptep = pte; > > Do we need now to call get_page() on the table as we are installing a > new PTE? Ouch, I really start mixing android branches with upstream... I thought this wasn't an issue because the host stage-2 doesn't refcount valid PTE... but this is only true on Android branches, not in the current upstream... So yes, you are right (and so were Wei-Lin who reported it as well on v1), I should move the if (counted) get_page() from PATCH2 into PATCH1. > > Also, I think we need a WRITE_ONCE() for the PTE write. This one though I am pretty sure it isn't needed because of the smp_store_release() when replacing the PTE with a table. > > Thanks, > Mostafa > > > + } > > +} > > + > > static int stage2_map_walk_leaf(const struct kvm_pgtable_visit_ctx *ctx, > > struct stage2_map_data *data) > > { > > struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops; > > + struct kvm_pgtable *pgt = data->mmu->pgt; > > kvm_pte_t *childp, new; > > int ret; > > > > @@ -1051,6 +1080,9 @@ static int stage2_map_walk_leaf(const struct kvm_pgtable_visit_ctx *ctx, > > if (!childp) > > return -ENOMEM; > > > > + if (pgt->flags & KVM_PGTABLE_S2_IDMAP) > > + stage2_map_prefault_idmap(ctx, childp); > > + > > if (!stage2_try_break_pte(ctx, data->mmu)) { > > mm_ops->put_page(childp); > > return -EAGAIN; > > -- > > 2.55.0.1007.g17ff1f9808-goog > > > > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. > > -- Vincent