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 X-Spam-Level: X-Spam-Status: No, score=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C166AC433DB for ; Fri, 5 Mar 2021 14:40:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9DA5264FD3 for ; Fri, 5 Mar 2021 14:40:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231293AbhCEOkH (ORCPT ); Fri, 5 Mar 2021 09:40:07 -0500 Received: from mail.kernel.org ([198.145.29.99]:37340 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231195AbhCEOjs (ORCPT ); Fri, 5 Mar 2021 09:39:48 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4222B64F48; Fri, 5 Mar 2021 14:39:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1614955187; bh=VaLrtV+MHU4qWVPa/LzAdaTtbUGASh0bgmLZUIbg9Io=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RUA6MS8JxyNhI6v8hXtjOkeNTLoys8qlrSFSFYksTa9xdyS3iimTi0+J9ZrhZ0Iq9 6psCeP+4TzPatiioUvcDUiQWgNcAGhgxmXefpH2HwMl8pxFiwnijw+YHowheSAkh7o lE6YRCePljoU4AKvXeDmSRYpJ9l2Gpf/aEntLb1Px/I0bW8GbNRUvkJQRKcw1lYOVn TzD2XoKjdcxMaYe0Prh8rnVugeiUHtJiRRD3Ox8AUXbV3IA51PjpXTqD5G36LnB+Tu BqUFvF3tVHaG6aZYSaYXEm6/EYJkF5cff2mxpAfCVLtUhgEaYSWiF2jJvNm0x/Hmre VFS8kuTA3xLtw== Date: Fri, 5 Mar 2021 14:39:42 +0000 From: Will Deacon To: Quentin Perret Cc: catalin.marinas@arm.com, maz@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, android-kvm@google.com, linux-kernel@vger.kernel.org, kernel-team@android.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, tabba@google.com, mark.rutland@arm.com, dbrazdil@google.com, mate.toth-pal@arm.com, seanjc@google.com, robh+dt@kernel.org Subject: Re: [PATCH v3 28/32] KVM: arm64: Add kvm_pgtable_stage2_idmap_greedy() Message-ID: <20210305143941.GA23017@willie-the-truck> References: <20210302150002.3685113-1-qperret@google.com> <20210302150002.3685113-29-qperret@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210302150002.3685113-29-qperret@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 02, 2021 at 02:59:58PM +0000, Quentin Perret wrote: > Add a new map function to the KVM page-table library that allows to > greedily create block identity-mappings. This will be useful to create > lazily the host stage 2 page-table as it will own most of memory and > will always be identity mapped. > > The new helper function creates the mapping in 2 steps: it first walks > the page-table to compute the largest possible granule that can be used > to idmap a given address without overriding existing incompatible > mappings; and then creates a mapping accordingly. > > Signed-off-by: Quentin Perret > --- > arch/arm64/include/asm/kvm_pgtable.h | 37 +++++++++ > arch/arm64/kvm/hyp/pgtable.c | 119 +++++++++++++++++++++++++++ > 2 files changed, 156 insertions(+) > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > index c9f6ed76e0ad..e51dcce69a5e 100644 > --- a/arch/arm64/include/asm/kvm_pgtable.h > +++ b/arch/arm64/include/asm/kvm_pgtable.h > @@ -96,6 +96,16 @@ enum kvm_pgtable_prot { > #define PAGE_HYP_RO (KVM_PGTABLE_PROT_R) > #define PAGE_HYP_DEVICE (PAGE_HYP | KVM_PGTABLE_PROT_DEVICE) > > +/** > + * struct kvm_mem_range - Range of Intermediate Physical Addresses > + * @start: Start of the range. > + * @end: End of the range. > + */ > +struct kvm_mem_range { > + u64 start; > + u64 end; > +}; > + > /** > * enum kvm_pgtable_walk_flags - Flags to control a depth-first page-table walk. > * @KVM_PGTABLE_WALK_LEAF: Visit leaf entries, including invalid > @@ -379,4 +389,31 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size); > int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size, > struct kvm_pgtable_walker *walker); > > +/** > + * kvm_pgtable_stage2_idmap_greedy() - Identity-map an Intermediate Physical > + * Address with a leaf entry at the highest > + * possible level. Not sure it's worth mentioning "highest possible level" here, as realistically the caller still has to provide a memcache to deal with the worst case and the structure of the page-table shouldn't matter. > + * @pgt: Page-table structure initialised by kvm_pgtable_*_init(). > + * @addr: Input address to identity-map. > + * @prot: Permissions and attributes for the mapping. > + * @range: Boundaries of the maximum memory region to map. > + * @mc: Cache of pre-allocated memory from which to allocate page-table > + * pages. > + * > + * This function attempts to install high-level identity-mappings covering @addr "high-level"? (again, I think I'd just drop this) > + * without overriding existing mappings with incompatible permissions or > + * attributes. An existing table entry may be coalesced into a block mapping > + * if and only if it covers @addr and all its leafs are either invalid and/or s/leafs/leaf entries/ > + * have permissions and attributes strictly matching @prot. The mapping is > + * guaranteed to be contained within the boundaries specified by @range at call > + * time. If only a subset of the memory specified by @range is mapped (because > + * of e.g. alignment issues or existing incompatible mappings), @range will be > + * updated accordingly. > + * > + * Return: 0 on success, negative error code on failure. > + */ > +int kvm_pgtable_stage2_idmap_greedy(struct kvm_pgtable *pgt, u64 addr, > + enum kvm_pgtable_prot prot, > + struct kvm_mem_range *range, > + void *mc); > #endif /* __ARM64_KVM_PGTABLE_H__ */ > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index 8aa01a9e2603..6897d771e2b2 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -987,3 +987,122 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt) > pgt->mm_ops->free_pages_exact(pgt->pgd, pgd_sz); > pgt->pgd = NULL; > } > + > +struct stage2_reduce_range_data { > + kvm_pte_t attr; > + u64 target_addr; > + u32 start_level; > + struct kvm_mem_range *range; > +}; > + > +static int __stage2_reduce_range(struct stage2_reduce_range_data *data, u64 addr) > +{ > + u32 level = data->start_level; > + > + for (; level < KVM_PGTABLE_MAX_LEVELS; level++) { > + u64 granule = kvm_granule_size(level); > + u64 start = ALIGN_DOWN(data->target_addr, granule); > + u64 end = start + granule; > + > + /* > + * The pinned address is in the current range, try one level > + * deeper. > + */ > + if (start == ALIGN_DOWN(addr, granule)) > + continue; > + > + /* > + * Make sure the current range is a reduction of the existing > + * range before updating it. > + */ > + if (data->range->start <= start && end <= data->range->end) { > + data->start_level = level; > + data->range->start = start; > + data->range->end = end; > + return 0; > + } > + } > + > + return -EINVAL; > +} > + > +#define KVM_PTE_LEAF_S2_COMPAT_MASK (KVM_PTE_LEAF_ATTR_S2_PERMS | \ > + KVM_PTE_LEAF_ATTR_LO_S2_MEMATTR | \ > + KVM_PTE_LEAF_SW_BIT_PROT_NONE) > + > +static int stage2_reduce_range_walker(u64 addr, u64 end, u32 level, > + kvm_pte_t *ptep, > + enum kvm_pgtable_walk_flags flag, > + void * const arg) > +{ > + struct stage2_reduce_range_data *data = arg; > + kvm_pte_t attr; > + int ret; > + > + if (addr < data->range->start || addr >= data->range->end) > + return 0; > + > + attr = *ptep & KVM_PTE_LEAF_S2_COMPAT_MASK; > + if (!attr || attr == data->attr) > + return 0; > + > + /* > + * An existing mapping with incompatible protection attributes is > + * 'pinned', so reduce the range if we hit one. > + */ > + ret = __stage2_reduce_range(data, addr); > + if (ret) > + return ret; > + > + return -EAGAIN; > +} > + > +static int stage2_reduce_range(struct kvm_pgtable *pgt, u64 addr, > + enum kvm_pgtable_prot prot, > + struct kvm_mem_range *range) > +{ > + struct stage2_reduce_range_data data = { > + .start_level = pgt->start_level, > + .range = range, > + .target_addr = addr, > + }; > + struct kvm_pgtable_walker walker = { > + .cb = stage2_reduce_range_walker, > + .flags = KVM_PGTABLE_WALK_LEAF, > + .arg = &data, > + }; > + int ret; > + > + data.attr = stage2_get_prot_attr(prot) & KVM_PTE_LEAF_S2_COMPAT_MASK; > + if (!data.attr) > + return -EINVAL; (this will need updating based on the other discussion we had) > + /* Reduce the kvm_mem_range to a granule size */ > + ret = __stage2_reduce_range(&data, range->end); > + if (ret) > + return ret; > + > + /* Walk the range to check permissions and reduce further if needed */ > + do { > + ret = kvm_pgtable_walk(pgt, range->start, range->end, &walker); (we spent some time debugging an issue here and you spotted that you're passing range->end instead of the size ;) > + } while (ret == -EAGAIN); I'm a bit nervous about this loop -- what guarantees forward progress here? Can we return to the host after a few tries instead? Will 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 X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55EBFC433E0 for ; Fri, 5 Mar 2021 14:39:54 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id B86AA64F34 for ; Fri, 5 Mar 2021 14:39:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B86AA64F34 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 40D354B543; Fri, 5 Mar 2021 09:39:53 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@kernel.org Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id CmRfqkwo0SH5; Fri, 5 Mar 2021 09:39:51 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id D8A5F4B559; Fri, 5 Mar 2021 09:39:51 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 542734B532 for ; Fri, 5 Mar 2021 09:39:50 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id I4M2zC4UHc8M for ; Fri, 5 Mar 2021 09:39:49 -0500 (EST) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id EDDFC4B234 for ; Fri, 5 Mar 2021 09:39:48 -0500 (EST) Received: by mail.kernel.org (Postfix) with ESMTPSA id 4222B64F48; Fri, 5 Mar 2021 14:39:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1614955187; bh=VaLrtV+MHU4qWVPa/LzAdaTtbUGASh0bgmLZUIbg9Io=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RUA6MS8JxyNhI6v8hXtjOkeNTLoys8qlrSFSFYksTa9xdyS3iimTi0+J9ZrhZ0Iq9 6psCeP+4TzPatiioUvcDUiQWgNcAGhgxmXefpH2HwMl8pxFiwnijw+YHowheSAkh7o lE6YRCePljoU4AKvXeDmSRYpJ9l2Gpf/aEntLb1Px/I0bW8GbNRUvkJQRKcw1lYOVn TzD2XoKjdcxMaYe0Prh8rnVugeiUHtJiRRD3Ox8AUXbV3IA51PjpXTqD5G36LnB+Tu BqUFvF3tVHaG6aZYSaYXEm6/EYJkF5cff2mxpAfCVLtUhgEaYSWiF2jJvNm0x/Hmre VFS8kuTA3xLtw== Date: Fri, 5 Mar 2021 14:39:42 +0000 From: Will Deacon To: Quentin Perret Subject: Re: [PATCH v3 28/32] KVM: arm64: Add kvm_pgtable_stage2_idmap_greedy() Message-ID: <20210305143941.GA23017@willie-the-truck> References: <20210302150002.3685113-1-qperret@google.com> <20210302150002.3685113-29-qperret@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210302150002.3685113-29-qperret@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Cc: android-kvm@google.com, catalin.marinas@arm.com, mate.toth-pal@arm.com, seanjc@google.com, tabba@google.com, linux-kernel@vger.kernel.org, robh+dt@kernel.org, linux-arm-kernel@lists.infradead.org, maz@kernel.org, kernel-team@android.com, kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Tue, Mar 02, 2021 at 02:59:58PM +0000, Quentin Perret wrote: > Add a new map function to the KVM page-table library that allows to > greedily create block identity-mappings. This will be useful to create > lazily the host stage 2 page-table as it will own most of memory and > will always be identity mapped. > > The new helper function creates the mapping in 2 steps: it first walks > the page-table to compute the largest possible granule that can be used > to idmap a given address without overriding existing incompatible > mappings; and then creates a mapping accordingly. > > Signed-off-by: Quentin Perret > --- > arch/arm64/include/asm/kvm_pgtable.h | 37 +++++++++ > arch/arm64/kvm/hyp/pgtable.c | 119 +++++++++++++++++++++++++++ > 2 files changed, 156 insertions(+) > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > index c9f6ed76e0ad..e51dcce69a5e 100644 > --- a/arch/arm64/include/asm/kvm_pgtable.h > +++ b/arch/arm64/include/asm/kvm_pgtable.h > @@ -96,6 +96,16 @@ enum kvm_pgtable_prot { > #define PAGE_HYP_RO (KVM_PGTABLE_PROT_R) > #define PAGE_HYP_DEVICE (PAGE_HYP | KVM_PGTABLE_PROT_DEVICE) > > +/** > + * struct kvm_mem_range - Range of Intermediate Physical Addresses > + * @start: Start of the range. > + * @end: End of the range. > + */ > +struct kvm_mem_range { > + u64 start; > + u64 end; > +}; > + > /** > * enum kvm_pgtable_walk_flags - Flags to control a depth-first page-table walk. > * @KVM_PGTABLE_WALK_LEAF: Visit leaf entries, including invalid > @@ -379,4 +389,31 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size); > int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size, > struct kvm_pgtable_walker *walker); > > +/** > + * kvm_pgtable_stage2_idmap_greedy() - Identity-map an Intermediate Physical > + * Address with a leaf entry at the highest > + * possible level. Not sure it's worth mentioning "highest possible level" here, as realistically the caller still has to provide a memcache to deal with the worst case and the structure of the page-table shouldn't matter. > + * @pgt: Page-table structure initialised by kvm_pgtable_*_init(). > + * @addr: Input address to identity-map. > + * @prot: Permissions and attributes for the mapping. > + * @range: Boundaries of the maximum memory region to map. > + * @mc: Cache of pre-allocated memory from which to allocate page-table > + * pages. > + * > + * This function attempts to install high-level identity-mappings covering @addr "high-level"? (again, I think I'd just drop this) > + * without overriding existing mappings with incompatible permissions or > + * attributes. An existing table entry may be coalesced into a block mapping > + * if and only if it covers @addr and all its leafs are either invalid and/or s/leafs/leaf entries/ > + * have permissions and attributes strictly matching @prot. The mapping is > + * guaranteed to be contained within the boundaries specified by @range at call > + * time. If only a subset of the memory specified by @range is mapped (because > + * of e.g. alignment issues or existing incompatible mappings), @range will be > + * updated accordingly. > + * > + * Return: 0 on success, negative error code on failure. > + */ > +int kvm_pgtable_stage2_idmap_greedy(struct kvm_pgtable *pgt, u64 addr, > + enum kvm_pgtable_prot prot, > + struct kvm_mem_range *range, > + void *mc); > #endif /* __ARM64_KVM_PGTABLE_H__ */ > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index 8aa01a9e2603..6897d771e2b2 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -987,3 +987,122 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt) > pgt->mm_ops->free_pages_exact(pgt->pgd, pgd_sz); > pgt->pgd = NULL; > } > + > +struct stage2_reduce_range_data { > + kvm_pte_t attr; > + u64 target_addr; > + u32 start_level; > + struct kvm_mem_range *range; > +}; > + > +static int __stage2_reduce_range(struct stage2_reduce_range_data *data, u64 addr) > +{ > + u32 level = data->start_level; > + > + for (; level < KVM_PGTABLE_MAX_LEVELS; level++) { > + u64 granule = kvm_granule_size(level); > + u64 start = ALIGN_DOWN(data->target_addr, granule); > + u64 end = start + granule; > + > + /* > + * The pinned address is in the current range, try one level > + * deeper. > + */ > + if (start == ALIGN_DOWN(addr, granule)) > + continue; > + > + /* > + * Make sure the current range is a reduction of the existing > + * range before updating it. > + */ > + if (data->range->start <= start && end <= data->range->end) { > + data->start_level = level; > + data->range->start = start; > + data->range->end = end; > + return 0; > + } > + } > + > + return -EINVAL; > +} > + > +#define KVM_PTE_LEAF_S2_COMPAT_MASK (KVM_PTE_LEAF_ATTR_S2_PERMS | \ > + KVM_PTE_LEAF_ATTR_LO_S2_MEMATTR | \ > + KVM_PTE_LEAF_SW_BIT_PROT_NONE) > + > +static int stage2_reduce_range_walker(u64 addr, u64 end, u32 level, > + kvm_pte_t *ptep, > + enum kvm_pgtable_walk_flags flag, > + void * const arg) > +{ > + struct stage2_reduce_range_data *data = arg; > + kvm_pte_t attr; > + int ret; > + > + if (addr < data->range->start || addr >= data->range->end) > + return 0; > + > + attr = *ptep & KVM_PTE_LEAF_S2_COMPAT_MASK; > + if (!attr || attr == data->attr) > + return 0; > + > + /* > + * An existing mapping with incompatible protection attributes is > + * 'pinned', so reduce the range if we hit one. > + */ > + ret = __stage2_reduce_range(data, addr); > + if (ret) > + return ret; > + > + return -EAGAIN; > +} > + > +static int stage2_reduce_range(struct kvm_pgtable *pgt, u64 addr, > + enum kvm_pgtable_prot prot, > + struct kvm_mem_range *range) > +{ > + struct stage2_reduce_range_data data = { > + .start_level = pgt->start_level, > + .range = range, > + .target_addr = addr, > + }; > + struct kvm_pgtable_walker walker = { > + .cb = stage2_reduce_range_walker, > + .flags = KVM_PGTABLE_WALK_LEAF, > + .arg = &data, > + }; > + int ret; > + > + data.attr = stage2_get_prot_attr(prot) & KVM_PTE_LEAF_S2_COMPAT_MASK; > + if (!data.attr) > + return -EINVAL; (this will need updating based on the other discussion we had) > + /* Reduce the kvm_mem_range to a granule size */ > + ret = __stage2_reduce_range(&data, range->end); > + if (ret) > + return ret; > + > + /* Walk the range to check permissions and reduce further if needed */ > + do { > + ret = kvm_pgtable_walk(pgt, range->start, range->end, &walker); (we spent some time debugging an issue here and you spotted that you're passing range->end instead of the size ;) > + } while (ret == -EAGAIN); I'm a bit nervous about this loop -- what guarantees forward progress here? Can we return to the host after a few tries instead? Will _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm 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 X-Spam-Level: X-Spam-Status: No, score=-15.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83E68C433DB for ; Fri, 5 Mar 2021 14:42:39 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 18C3864F48 for ; Fri, 5 Mar 2021 14:42:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 18C3864F48 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=/NTgnwZdTHo0CMXZwicASPnW4OCMrbl/Hom7ZWNnzFY=; b=Ql+amZkrbcDlQXOCI0E/b8mAS mtGJk6y+JmQKrQ51inGpIdYXFUL0DbBkMzoBlo8gF5p5QZPeYffjx9RETSkAajmuDKxYffGSScngV fYfN8UqN+bw9DHbJKWlaPtGYbAroxqfuDtFWCcncUpJZPn99HJmM7PHyFXGhpxh6fDjxZ6ro/EMgq 9QsuM9+HHX84whya7WM5esq0leTJry9XLYKkBF5S3XGtxrTktaNzfImrwN5fcL0lUvgeWYTnrKrzj lgRvhj1zH05XFPkxFP1NVqDJKpPBoqaZTGf6c2G55ppuzN3qBYOEHL2jUiQReccKGAWy7gcQ838TI T+vKyeudg==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lIBcg-00FKdb-SZ; Fri, 05 Mar 2021 14:40:11 +0000 Received: from mail.kernel.org ([198.145.29.99]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lIBcN-00FKai-E3 for linux-arm-kernel@lists.infradead.org; Fri, 05 Mar 2021 14:39:57 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4222B64F48; Fri, 5 Mar 2021 14:39:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1614955187; bh=VaLrtV+MHU4qWVPa/LzAdaTtbUGASh0bgmLZUIbg9Io=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RUA6MS8JxyNhI6v8hXtjOkeNTLoys8qlrSFSFYksTa9xdyS3iimTi0+J9ZrhZ0Iq9 6psCeP+4TzPatiioUvcDUiQWgNcAGhgxmXefpH2HwMl8pxFiwnijw+YHowheSAkh7o lE6YRCePljoU4AKvXeDmSRYpJ9l2Gpf/aEntLb1Px/I0bW8GbNRUvkJQRKcw1lYOVn TzD2XoKjdcxMaYe0Prh8rnVugeiUHtJiRRD3Ox8AUXbV3IA51PjpXTqD5G36LnB+Tu BqUFvF3tVHaG6aZYSaYXEm6/EYJkF5cff2mxpAfCVLtUhgEaYSWiF2jJvNm0x/Hmre VFS8kuTA3xLtw== Date: Fri, 5 Mar 2021 14:39:42 +0000 From: Will Deacon To: Quentin Perret Cc: catalin.marinas@arm.com, maz@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, android-kvm@google.com, linux-kernel@vger.kernel.org, kernel-team@android.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, tabba@google.com, mark.rutland@arm.com, dbrazdil@google.com, mate.toth-pal@arm.com, seanjc@google.com, robh+dt@kernel.org Subject: Re: [PATCH v3 28/32] KVM: arm64: Add kvm_pgtable_stage2_idmap_greedy() Message-ID: <20210305143941.GA23017@willie-the-truck> References: <20210302150002.3685113-1-qperret@google.com> <20210302150002.3685113-29-qperret@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210302150002.3685113-29-qperret@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210305_143955_766812_AC2595E2 X-CRM114-Status: GOOD ( 35.43 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Mar 02, 2021 at 02:59:58PM +0000, Quentin Perret wrote: > Add a new map function to the KVM page-table library that allows to > greedily create block identity-mappings. This will be useful to create > lazily the host stage 2 page-table as it will own most of memory and > will always be identity mapped. > > The new helper function creates the mapping in 2 steps: it first walks > the page-table to compute the largest possible granule that can be used > to idmap a given address without overriding existing incompatible > mappings; and then creates a mapping accordingly. > > Signed-off-by: Quentin Perret > --- > arch/arm64/include/asm/kvm_pgtable.h | 37 +++++++++ > arch/arm64/kvm/hyp/pgtable.c | 119 +++++++++++++++++++++++++++ > 2 files changed, 156 insertions(+) > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > index c9f6ed76e0ad..e51dcce69a5e 100644 > --- a/arch/arm64/include/asm/kvm_pgtable.h > +++ b/arch/arm64/include/asm/kvm_pgtable.h > @@ -96,6 +96,16 @@ enum kvm_pgtable_prot { > #define PAGE_HYP_RO (KVM_PGTABLE_PROT_R) > #define PAGE_HYP_DEVICE (PAGE_HYP | KVM_PGTABLE_PROT_DEVICE) > > +/** > + * struct kvm_mem_range - Range of Intermediate Physical Addresses > + * @start: Start of the range. > + * @end: End of the range. > + */ > +struct kvm_mem_range { > + u64 start; > + u64 end; > +}; > + > /** > * enum kvm_pgtable_walk_flags - Flags to control a depth-first page-table walk. > * @KVM_PGTABLE_WALK_LEAF: Visit leaf entries, including invalid > @@ -379,4 +389,31 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size); > int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size, > struct kvm_pgtable_walker *walker); > > +/** > + * kvm_pgtable_stage2_idmap_greedy() - Identity-map an Intermediate Physical > + * Address with a leaf entry at the highest > + * possible level. Not sure it's worth mentioning "highest possible level" here, as realistically the caller still has to provide a memcache to deal with the worst case and the structure of the page-table shouldn't matter. > + * @pgt: Page-table structure initialised by kvm_pgtable_*_init(). > + * @addr: Input address to identity-map. > + * @prot: Permissions and attributes for the mapping. > + * @range: Boundaries of the maximum memory region to map. > + * @mc: Cache of pre-allocated memory from which to allocate page-table > + * pages. > + * > + * This function attempts to install high-level identity-mappings covering @addr "high-level"? (again, I think I'd just drop this) > + * without overriding existing mappings with incompatible permissions or > + * attributes. An existing table entry may be coalesced into a block mapping > + * if and only if it covers @addr and all its leafs are either invalid and/or s/leafs/leaf entries/ > + * have permissions and attributes strictly matching @prot. The mapping is > + * guaranteed to be contained within the boundaries specified by @range at call > + * time. If only a subset of the memory specified by @range is mapped (because > + * of e.g. alignment issues or existing incompatible mappings), @range will be > + * updated accordingly. > + * > + * Return: 0 on success, negative error code on failure. > + */ > +int kvm_pgtable_stage2_idmap_greedy(struct kvm_pgtable *pgt, u64 addr, > + enum kvm_pgtable_prot prot, > + struct kvm_mem_range *range, > + void *mc); > #endif /* __ARM64_KVM_PGTABLE_H__ */ > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index 8aa01a9e2603..6897d771e2b2 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -987,3 +987,122 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt) > pgt->mm_ops->free_pages_exact(pgt->pgd, pgd_sz); > pgt->pgd = NULL; > } > + > +struct stage2_reduce_range_data { > + kvm_pte_t attr; > + u64 target_addr; > + u32 start_level; > + struct kvm_mem_range *range; > +}; > + > +static int __stage2_reduce_range(struct stage2_reduce_range_data *data, u64 addr) > +{ > + u32 level = data->start_level; > + > + for (; level < KVM_PGTABLE_MAX_LEVELS; level++) { > + u64 granule = kvm_granule_size(level); > + u64 start = ALIGN_DOWN(data->target_addr, granule); > + u64 end = start + granule; > + > + /* > + * The pinned address is in the current range, try one level > + * deeper. > + */ > + if (start == ALIGN_DOWN(addr, granule)) > + continue; > + > + /* > + * Make sure the current range is a reduction of the existing > + * range before updating it. > + */ > + if (data->range->start <= start && end <= data->range->end) { > + data->start_level = level; > + data->range->start = start; > + data->range->end = end; > + return 0; > + } > + } > + > + return -EINVAL; > +} > + > +#define KVM_PTE_LEAF_S2_COMPAT_MASK (KVM_PTE_LEAF_ATTR_S2_PERMS | \ > + KVM_PTE_LEAF_ATTR_LO_S2_MEMATTR | \ > + KVM_PTE_LEAF_SW_BIT_PROT_NONE) > + > +static int stage2_reduce_range_walker(u64 addr, u64 end, u32 level, > + kvm_pte_t *ptep, > + enum kvm_pgtable_walk_flags flag, > + void * const arg) > +{ > + struct stage2_reduce_range_data *data = arg; > + kvm_pte_t attr; > + int ret; > + > + if (addr < data->range->start || addr >= data->range->end) > + return 0; > + > + attr = *ptep & KVM_PTE_LEAF_S2_COMPAT_MASK; > + if (!attr || attr == data->attr) > + return 0; > + > + /* > + * An existing mapping with incompatible protection attributes is > + * 'pinned', so reduce the range if we hit one. > + */ > + ret = __stage2_reduce_range(data, addr); > + if (ret) > + return ret; > + > + return -EAGAIN; > +} > + > +static int stage2_reduce_range(struct kvm_pgtable *pgt, u64 addr, > + enum kvm_pgtable_prot prot, > + struct kvm_mem_range *range) > +{ > + struct stage2_reduce_range_data data = { > + .start_level = pgt->start_level, > + .range = range, > + .target_addr = addr, > + }; > + struct kvm_pgtable_walker walker = { > + .cb = stage2_reduce_range_walker, > + .flags = KVM_PGTABLE_WALK_LEAF, > + .arg = &data, > + }; > + int ret; > + > + data.attr = stage2_get_prot_attr(prot) & KVM_PTE_LEAF_S2_COMPAT_MASK; > + if (!data.attr) > + return -EINVAL; (this will need updating based on the other discussion we had) > + /* Reduce the kvm_mem_range to a granule size */ > + ret = __stage2_reduce_range(&data, range->end); > + if (ret) > + return ret; > + > + /* Walk the range to check permissions and reduce further if needed */ > + do { > + ret = kvm_pgtable_walk(pgt, range->start, range->end, &walker); (we spent some time debugging an issue here and you spotted that you're passing range->end instead of the size ;) > + } while (ret == -EAGAIN); I'm a bit nervous about this loop -- what guarantees forward progress here? Can we return to the host after a few tries instead? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel