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Date: Tue, 4 Jul 2023 15:40:01 +0800
From: Yuan Yao <yuan.yao@...ux.intel.com>
To: Kai Huang <kai.huang@...el.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
linux-mm@...ck.org, x86@...nel.org, dave.hansen@...el.com,
kirill.shutemov@...ux.intel.com, tony.luck@...el.com,
peterz@...radead.org, tglx@...utronix.de, bp@...en8.de,
mingo@...hat.com, hpa@...or.com, seanjc@...gle.com,
pbonzini@...hat.com, david@...hat.com, dan.j.williams@...el.com,
rafael.j.wysocki@...el.com, ashok.raj@...el.com,
reinette.chatre@...el.com, len.brown@...el.com, ak@...ux.intel.com,
isaku.yamahata@...el.com, ying.huang@...el.com, chao.gao@...el.com,
sathyanarayanan.kuppuswamy@...ux.intel.com, nik.borisov@...e.com,
bagasdotme@...il.com, sagis@...gle.com, imammedo@...hat.com
Subject: Re: [PATCH v12 12/22] x86/virt/tdx: Allocate and set up PAMTs for
TDMRs
On Tue, Jun 27, 2023 at 02:12:42AM +1200, Kai Huang wrote:
> The TDX module uses additional metadata to record things like which
> guest "owns" a given page of memory. This metadata, referred as
> Physical Address Metadata Table (PAMT), essentially serves as the
> 'struct page' for the TDX module. PAMTs are not reserved by hardware
> up front. They must be allocated by the kernel and then given to the
> TDX module during module initialization.
>
> TDX supports 3 page sizes: 4K, 2M, and 1G. Each "TD Memory Region"
> (TDMR) has 3 PAMTs to track the 3 supported page sizes. Each PAMT must
> be a physically contiguous area from a Convertible Memory Region (CMR).
> However, the PAMTs which track pages in one TDMR do not need to reside
> within that TDMR but can be anywhere in CMRs. If one PAMT overlaps with
> any TDMR, the overlapping part must be reported as a reserved area in
> that particular TDMR.
>
> Use alloc_contig_pages() since PAMT must be a physically contiguous area
> and it may be potentially large (~1/256th of the size of the given TDMR).
> The downside is alloc_contig_pages() may fail at runtime. One (bad)
> mitigation is to launch a TDX guest early during system boot to get
> those PAMTs allocated at early time, but the only way to fix is to add a
> boot option to allocate or reserve PAMTs during kernel boot.
>
> It is imperfect but will be improved on later.
>
> TDX only supports a limited number of reserved areas per TDMR to cover
> both PAMTs and memory holes within the given TDMR. If many PAMTs are
> allocated within a single TDMR, the reserved areas may not be sufficient
> to cover all of them.
>
> Adopt the following policies when allocating PAMTs for a given TDMR:
>
> - Allocate three PAMTs of the TDMR in one contiguous chunk to minimize
> the total number of reserved areas consumed for PAMTs.
> - Try to first allocate PAMT from the local node of the TDMR for better
> NUMA locality.
>
> Also dump out how many pages are allocated for PAMTs when the TDX module
> is initialized successfully. This helps answer the eternal "where did
> all my memory go?" questions.
>
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> Reviewed-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>
> ---
>
> v11 -> v12:
> - Moved TDX_PS_NUM from tdx.c to <asm/tdx.h> (Kirill)
> - "<= TDX_PS_1G" -> "< TDX_PS_NUM" (Kirill)
> - Changed tdmr_get_pamt() to return base and size instead of base_pfn
> and npages and related code directly (Dave).
> - Simplified PAMT kb counting. (Dave)
> - tdmrs_count_pamt_pages() -> tdmr_count_pamt_kb() (Kirill/Dave)
>
> v10 -> v11:
> - No update
>
> v9 -> v10:
> - Removed code change in disable_tdx_module() as it doesn't exist
> anymore.
>
> v8 -> v9:
> - Added TDX_PS_NR macro instead of open-coding (Dave).
> - Better alignment of 'pamt_entry_size' in tdmr_set_up_pamt() (Dave).
> - Changed to print out PAMTs in "KBs" instead of "pages" (Dave).
> - Added Dave's Reviewed-by.
>
> v7 -> v8: (Dave)
> - Changelog:
> - Added a sentence to state PAMT allocation will be improved.
> - Others suggested by Dave.
> - Moved 'nid' of 'struct tdx_memblock' to this patch.
> - Improved comments around tdmr_get_nid().
> - WARN_ON_ONCE() -> pr_warn() in tdmr_get_nid().
> - Other changes due to 'struct tdmr_info_list'.
>
> v6 -> v7:
> - Changes due to using macros instead of 'enum' for TDX supported page
> sizes.
>
> v5 -> v6:
> - Rebase due to using 'tdx_memblock' instead of memblock.
> - 'int pamt_entry_nr' -> 'unsigned long nr_pamt_entries' (Dave/Sagis).
> - Improved comment around tdmr_get_nid() (Dave).
> - Improved comment in tdmr_set_up_pamt() around breaking the PAMT
> into PAMTs for 4K/2M/1G (Dave).
> - tdmrs_get_pamt_pages() -> tdmrs_count_pamt_pages() (Dave).
>
> - v3 -> v5 (no feedback on v4):
> - Used memblock to get the NUMA node for given TDMR.
> - Removed tdmr_get_pamt_sz() helper but use open-code instead.
> - Changed to use 'switch .. case..' for each TDX supported page size in
> tdmr_get_pamt_sz() (the original __tdmr_get_pamt_sz()).
> - Added printing out memory used for PAMT allocation when TDX module is
> initialized successfully.
> - Explained downside of alloc_contig_pages() in changelog.
> - Addressed other minor comments.
>
>
> ---
> arch/x86/Kconfig | 1 +
> arch/x86/include/asm/tdx.h | 1 +
> arch/x86/virt/vmx/tdx/tdx.c | 215 +++++++++++++++++++++++++++++++++++-
> arch/x86/virt/vmx/tdx/tdx.h | 1 +
> 4 files changed, 213 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 2226d8a4c749..ad364f01de33 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1959,6 +1959,7 @@ config INTEL_TDX_HOST
> depends on KVM_INTEL
> depends on X86_X2APIC
> select ARCH_KEEP_MEMBLOCK
> + depends on CONTIG_ALLOC
> help
> Intel Trust Domain Extensions (TDX) protects guest VMs from malicious
> host and certain physical attacks. This option enables necessary TDX
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index d8226a50c58c..91416fd600cd 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -24,6 +24,7 @@
> #define TDX_PS_4K 0
> #define TDX_PS_2M 1
> #define TDX_PS_1G 2
> +#define TDX_PS_NR (TDX_PS_1G + 1)
>
> /*
> * Used to gather the output registers values of the TDCALL and SEAMCALL
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index 2ffc1517a93b..fd5417577f26 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -221,7 +221,7 @@ static int tdx_get_sysinfo(struct tdsysinfo_struct *sysinfo,
> * overlap.
> */
> static int add_tdx_memblock(struct list_head *tmb_list, unsigned long start_pfn,
> - unsigned long end_pfn)
> + unsigned long end_pfn, int nid)
> {
> struct tdx_memblock *tmb;
>
> @@ -232,6 +232,7 @@ static int add_tdx_memblock(struct list_head *tmb_list, unsigned long start_pfn,
> INIT_LIST_HEAD(&tmb->list);
> tmb->start_pfn = start_pfn;
> tmb->end_pfn = end_pfn;
> + tmb->nid = nid;
>
> /* @tmb_list is protected by mem_hotplug_lock */
> list_add_tail(&tmb->list, tmb_list);
> @@ -259,9 +260,9 @@ static void free_tdx_memlist(struct list_head *tmb_list)
> static int build_tdx_memlist(struct list_head *tmb_list)
> {
> unsigned long start_pfn, end_pfn;
> - int i, ret;
> + int i, nid, ret;
>
> - for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, NULL) {
> + for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) {
> /*
> * The first 1MB is not reported as TDX convertible memory.
> * Although the first 1MB is always reserved and won't end up
> @@ -277,7 +278,7 @@ static int build_tdx_memlist(struct list_head *tmb_list)
> * memblock has already guaranteed they are in address
> * ascending order and don't overlap.
> */
> - ret = add_tdx_memblock(tmb_list, start_pfn, end_pfn);
> + ret = add_tdx_memblock(tmb_list, start_pfn, end_pfn, nid);
> if (ret)
> goto err;
> }
> @@ -437,6 +438,202 @@ static int fill_out_tdmrs(struct list_head *tmb_list,
> return 0;
> }
>
> +/*
> + * Calculate PAMT size given a TDMR and a page size. The returned
> + * PAMT size is always aligned up to 4K page boundary.
> + */
> +static unsigned long tdmr_get_pamt_sz(struct tdmr_info *tdmr, int pgsz,
> + u16 pamt_entry_size)
> +{
> + unsigned long pamt_sz, nr_pamt_entries;
> +
> + switch (pgsz) {
> + case TDX_PS_4K:
> + nr_pamt_entries = tdmr->size >> PAGE_SHIFT;
> + break;
> + case TDX_PS_2M:
> + nr_pamt_entries = tdmr->size >> PMD_SHIFT;
> + break;
> + case TDX_PS_1G:
> + nr_pamt_entries = tdmr->size >> PUD_SHIFT;
> + break;
> + default:
> + WARN_ON_ONCE(1);
> + return 0;
> + }
> +
> + pamt_sz = nr_pamt_entries * pamt_entry_size;
> + /* TDX requires PAMT size must be 4K aligned */
> + pamt_sz = ALIGN(pamt_sz, PAGE_SIZE);
> +
> + return pamt_sz;
> +}
> +
> +/*
> + * Locate a NUMA node which should hold the allocation of the @tdmr
> + * PAMT. This node will have some memory covered by the TDMR. The
> + * relative amount of memory covered is not considered.
> + */
> +static int tdmr_get_nid(struct tdmr_info *tdmr, struct list_head *tmb_list)
> +{
> + struct tdx_memblock *tmb;
> +
> + /*
> + * A TDMR must cover at least part of one TMB. That TMB will end
> + * after the TDMR begins. But, that TMB may have started before
> + * the TDMR. Find the next 'tmb' that _ends_ after this TDMR
> + * begins. Ignore 'tmb' start addresses. They are irrelevant.
> + */
> + list_for_each_entry(tmb, tmb_list, list) {
> + if (tmb->end_pfn > PHYS_PFN(tdmr->base))
> + return tmb->nid;
> + }
> +
> + /*
> + * Fall back to allocating the TDMR's metadata from node 0 when
> + * no TDX memory block can be found. This should never happen
> + * since TDMRs originate from TDX memory blocks.
> + */
> + pr_warn("TDMR [0x%llx, 0x%llx): unable to find local NUMA node for PAMT allocation, fallback to use node 0.\n",
> + tdmr->base, tdmr_end(tdmr));
> + return 0;
> +}
> +
> +/*
> + * Allocate PAMTs from the local NUMA node of some memory in @tmb_list
> + * within @tdmr, and set up PAMTs for @tdmr.
> + */
> +static int tdmr_set_up_pamt(struct tdmr_info *tdmr,
> + struct list_head *tmb_list,
> + u16 pamt_entry_size)
> +{
> + unsigned long pamt_base[TDX_PS_NR];
> + unsigned long pamt_size[TDX_PS_NR];
> + unsigned long tdmr_pamt_base;
> + unsigned long tdmr_pamt_size;
> + struct page *pamt;
> + int pgsz, nid;
> +
> + nid = tdmr_get_nid(tdmr, tmb_list);
> +
> + /*
> + * Calculate the PAMT size for each TDX supported page size
> + * and the total PAMT size.
> + */
> + tdmr_pamt_size = 0;
> + for (pgsz = TDX_PS_4K; pgsz < TDX_PS_NR ; pgsz++) {
^
Please remove the additional space.
Reviewed-by: Yuan Yao <yuan.yao@...el.com>
> + pamt_size[pgsz] = tdmr_get_pamt_sz(tdmr, pgsz,
> + pamt_entry_size);
> + tdmr_pamt_size += pamt_size[pgsz];
> + }
> +
> + /*
> + * Allocate one chunk of physically contiguous memory for all
> + * PAMTs. This helps minimize the PAMT's use of reserved areas
> + * in overlapped TDMRs.
> + */
> + pamt = alloc_contig_pages(tdmr_pamt_size >> PAGE_SHIFT, GFP_KERNEL,
> + nid, &node_online_map);
> + if (!pamt)
> + return -ENOMEM;
> +
> + /*
> + * Break the contiguous allocation back up into the
> + * individual PAMTs for each page size.
> + */
> + tdmr_pamt_base = page_to_pfn(pamt) << PAGE_SHIFT;
> + for (pgsz = TDX_PS_4K; pgsz < TDX_PS_NR; pgsz++) {
> + pamt_base[pgsz] = tdmr_pamt_base;
> + tdmr_pamt_base += pamt_size[pgsz];
> + }
> +
> + tdmr->pamt_4k_base = pamt_base[TDX_PS_4K];
> + tdmr->pamt_4k_size = pamt_size[TDX_PS_4K];
> + tdmr->pamt_2m_base = pamt_base[TDX_PS_2M];
> + tdmr->pamt_2m_size = pamt_size[TDX_PS_2M];
> + tdmr->pamt_1g_base = pamt_base[TDX_PS_1G];
> + tdmr->pamt_1g_size = pamt_size[TDX_PS_1G];
> +
> + return 0;
> +}
> +
> +static void tdmr_get_pamt(struct tdmr_info *tdmr, unsigned long *pamt_base,
> + unsigned long *pamt_size)
> +{
> + unsigned long pamt_bs, pamt_sz;
> +
> + /*
> + * The PAMT was allocated in one contiguous unit. The 4K PAMT
> + * should always point to the beginning of that allocation.
> + */
> + pamt_bs = tdmr->pamt_4k_base;
> + pamt_sz = tdmr->pamt_4k_size + tdmr->pamt_2m_size + tdmr->pamt_1g_size;
> +
> + WARN_ON_ONCE((pamt_bs & ~PAGE_MASK) || (pamt_sz & ~PAGE_MASK));
> +
> + *pamt_base = pamt_bs;
> + *pamt_size = pamt_sz;
> +}
> +
> +static void tdmr_free_pamt(struct tdmr_info *tdmr)
> +{
> + unsigned long pamt_base, pamt_size;
> +
> + tdmr_get_pamt(tdmr, &pamt_base, &pamt_size);
> +
> + /* Do nothing if PAMT hasn't been allocated for this TDMR */
> + if (!pamt_size)
> + return;
> +
> + if (WARN_ON_ONCE(!pamt_base))
> + return;
> +
> + free_contig_range(pamt_base >> PAGE_SHIFT, pamt_size >> PAGE_SHIFT);
> +}
> +
> +static void tdmrs_free_pamt_all(struct tdmr_info_list *tdmr_list)
> +{
> + int i;
> +
> + for (i = 0; i < tdmr_list->nr_consumed_tdmrs; i++)
> + tdmr_free_pamt(tdmr_entry(tdmr_list, i));
> +}
> +
> +/* Allocate and set up PAMTs for all TDMRs */
> +static int tdmrs_set_up_pamt_all(struct tdmr_info_list *tdmr_list,
> + struct list_head *tmb_list,
> + u16 pamt_entry_size)
> +{
> + int i, ret = 0;
> +
> + for (i = 0; i < tdmr_list->nr_consumed_tdmrs; i++) {
> + ret = tdmr_set_up_pamt(tdmr_entry(tdmr_list, i), tmb_list,
> + pamt_entry_size);
> + if (ret)
> + goto err;
> + }
> +
> + return 0;
> +err:
> + tdmrs_free_pamt_all(tdmr_list);
> + return ret;
> +}
> +
> +static unsigned long tdmrs_count_pamt_kb(struct tdmr_info_list *tdmr_list)
> +{
> + unsigned long pamt_size = 0;
> + int i;
> +
> + for (i = 0; i < tdmr_list->nr_consumed_tdmrs; i++) {
> + unsigned long base, size;
> +
> + tdmr_get_pamt(tdmr_entry(tdmr_list, i), &base, &size);
> + pamt_size += size;
> + }
> +
> + return pamt_size / 1024;
> +}
> +
> /*
> * Construct a list of TDMRs on the preallocated space in @tdmr_list
> * to cover all TDX memory regions in @tmb_list based on the TDX module
> @@ -452,10 +649,13 @@ static int construct_tdmrs(struct list_head *tmb_list,
> if (ret)
> return ret;
>
> + ret = tdmrs_set_up_pamt_all(tdmr_list, tmb_list,
> + sysinfo->pamt_entry_size);
> + if (ret)
> + return ret;
> /*
> * TODO:
> *
> - * - Allocate and set up PAMTs for each TDMR.
> * - Designate reserved areas for each TDMR.
> *
> * Return -EINVAL until constructing TDMRs is done
> @@ -526,6 +726,11 @@ static int init_tdx_module(void)
> * Return error before all steps are done.
> */
> ret = -EINVAL;
> + if (ret)
> + tdmrs_free_pamt_all(&tdmr_list);
> + else
> + pr_info("%lu KBs allocated for PAMT.\n",
> + tdmrs_count_pamt_kb(&tdmr_list));
> out_free_tdmrs:
> /*
> * Always free the buffer of TDMRs as they are only used during
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index 3086f7ad0522..9b5a65f37e8b 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -121,6 +121,7 @@ struct tdx_memblock {
> struct list_head list;
> unsigned long start_pfn;
> unsigned long end_pfn;
> + int nid;
> };
>
> /* Warn if kernel has less than TDMR_NR_WARN TDMRs after allocation */
> --
> 2.40.1
>
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