Re: [PATCH v36 08/24] x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections

[Darren Kenny]

On Thursday, 2020-07-16 at 16:52:47 +03, Jarkko Sakkinen wrote:
> From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
>
> Enumerate Enclave Page Cache (EPC) sections via CPUID and add the data
> structures necessary to track EPC pages so that they can be easily borrowed
> for different uses.
>
> Embed section index to the first eight bits of the EPC page descriptor.
> Existing client hardware supports only a single section, while upcoming
> server hardware will support at most eight sections. Thus, eight bits
> should be enough for long term needs.
>
> Acked-by: Jethro Beekman <jethro@xxxxxxxxxxxx>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Co-developed-by: Serge Ayoun <serge.ayoun@xxxxxxxxx>
> Signed-off-by: Serge Ayoun <serge.ayoun@xxxxxxxxx>
> Co-developed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>

Reviewed-by: Darren Kenny <darren.kenny@xxxxxxxxxx>

> ---
>  arch/x86/Kconfig                 |  17 +++
>  arch/x86/kernel/cpu/Makefile     |   1 +
>  arch/x86/kernel/cpu/sgx/Makefile |   2 +
>  arch/x86/kernel/cpu/sgx/main.c   | 216 +++++++++++++++++++++++++++++++
>  arch/x86/kernel/cpu/sgx/sgx.h    |  52 ++++++++
>  5 files changed, 288 insertions(+)
>  create mode 100644 arch/x86/kernel/cpu/sgx/Makefile
>  create mode 100644 arch/x86/kernel/cpu/sgx/main.c
>  create mode 100644 arch/x86/kernel/cpu/sgx/sgx.h
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 883da0abf779..0dea7fdd7a00 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1926,6 +1926,23 @@ config X86_INTEL_TSX_MODE_AUTO
>  	  side channel attacks- equals the tsx=auto command line parameter.
>  endchoice
>  
> +config INTEL_SGX
> +	bool "Intel SGX"
> +	depends on X86_64 && CPU_SUP_INTEL
> +	depends on CRYPTO=y
> +	depends on CRYPTO_SHA256=y
> +	select SRCU
> +	select MMU_NOTIFIER
> +	help
> +	  Intel(R) Software Guard eXtensions (SGX) is a set of CPU instructions
> +	  that can be used by applications to set aside private regions of code
> +	  and data, referred to as enclaves. An enclave's private memory can
> +	  only be accessed by code running within the enclave. Accesses from
> +	  outside the enclave, including other enclaves, are disallowed by
> +	  hardware.
> +
> +	  If unsure, say N.
> +
>  config EFI
>  	bool "EFI runtime service support"
>  	depends on ACPI
> diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
> index dba6a83bc349..b00f801601f3 100644
> --- a/arch/x86/kernel/cpu/Makefile
> +++ b/arch/x86/kernel/cpu/Makefile
> @@ -49,6 +49,7 @@ obj-$(CONFIG_X86_MCE)			+= mce/
>  obj-$(CONFIG_MTRR)			+= mtrr/
>  obj-$(CONFIG_MICROCODE)			+= microcode/
>  obj-$(CONFIG_X86_CPU_RESCTRL)		+= resctrl/
> +obj-$(CONFIG_INTEL_SGX)			+= sgx/
>  
>  obj-$(CONFIG_X86_LOCAL_APIC)		+= perfctr-watchdog.o
>  
> diff --git a/arch/x86/kernel/cpu/sgx/Makefile b/arch/x86/kernel/cpu/sgx/Makefile
> new file mode 100644
> index 000000000000..79510ce01b3b
> --- /dev/null
> +++ b/arch/x86/kernel/cpu/sgx/Makefile
> @@ -0,0 +1,2 @@
> +obj-y += \
> +	main.o
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> new file mode 100644
> index 000000000000..c5831e3db14a
> --- /dev/null
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -0,0 +1,216 @@
> +// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
> +// Copyright(c) 2016-17 Intel Corporation.
> +
> +#include <linux/freezer.h>
> +#include <linux/highmem.h>
> +#include <linux/kthread.h>
> +#include <linux/pagemap.h>
> +#include <linux/ratelimit.h>
> +#include <linux/sched/mm.h>
> +#include <linux/sched/signal.h>
> +#include <linux/slab.h>
> +#include "encls.h"
> +
> +struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];
> +static int sgx_nr_epc_sections;
> +static struct task_struct *ksgxswapd_tsk;
> +
> +static void sgx_sanitize_section(struct sgx_epc_section *section)
> +{
> +	struct sgx_epc_page *page;
> +	LIST_HEAD(secs_list);
> +	int ret;
> +
> +	while (!list_empty(&section->unsanitized_page_list)) {
> +		if (kthread_should_stop())
> +			return;
> +
> +		spin_lock(&section->lock);
> +
> +		page = list_first_entry(&section->unsanitized_page_list,
> +					struct sgx_epc_page, list);
> +
> +		ret = __eremove(sgx_get_epc_addr(page));
> +		if (!ret)
> +			list_move(&page->list, &section->page_list);
> +		else
> +			list_move_tail(&page->list, &secs_list);
> +
> +		spin_unlock(&section->lock);
> +
> +		cond_resched();
> +	}
> +}
> +
> +static int ksgxswapd(void *p)
> +{
> +	int i;
> +
> +	set_freezable();
> +
> +	/*
> +	 * Reset all pages to uninitialized state. Pages could be in initialized
> +	 * on kmemexec.
> +	 */
> +	for (i = 0; i < sgx_nr_epc_sections; i++)
> +		sgx_sanitize_section(&sgx_epc_sections[i]);
> +
> +	/*
> +	 * 2nd round for the SECS pages as they cannot be removed when they
> +	 * still hold child pages.
> +	 */
> +	for (i = 0; i < sgx_nr_epc_sections; i++) {
> +		sgx_sanitize_section(&sgx_epc_sections[i]);
> +
> +		/* Should never happen. */
> +		if (!list_empty(&sgx_epc_sections[i].unsanitized_page_list))
> +			WARN(1, "EPC section %d has unsanitized pages.\n", i);
> +	}
> +
> +	return 0;
> +}
> +
> +static bool __init sgx_page_reclaimer_init(void)
> +{
> +	struct task_struct *tsk;
> +
> +	tsk = kthread_run(ksgxswapd, NULL, "ksgxswapd");
> +	if (IS_ERR(tsk))
> +		return false;
> +
> +	ksgxswapd_tsk = tsk;
> +
> +	return true;
> +}
> +
> +static void __init sgx_free_epc_section(struct sgx_epc_section *section)
> +{
> +	struct sgx_epc_page *page;
> +
> +	while (!list_empty(&section->page_list)) {
> +		page = list_first_entry(&section->page_list,
> +					struct sgx_epc_page, list);
> +		list_del(&page->list);
> +		kfree(page);
> +	}
> +
> +	while (!list_empty(&section->unsanitized_page_list)) {
> +		page = list_first_entry(&section->unsanitized_page_list,
> +					struct sgx_epc_page, list);
> +		list_del(&page->list);
> +		kfree(page);
> +	}
> +
> +	memunmap(section->va);
> +}
> +
> +static bool __init sgx_setup_epc_section(u64 addr, u64 size,
> +					 unsigned long index,
> +					 struct sgx_epc_section *section)
> +{
> +	unsigned long nr_pages = size >> PAGE_SHIFT;
> +	struct sgx_epc_page *page;
> +	unsigned long i;
> +
> +	section->va = memremap(addr, size, MEMREMAP_WB);
> +	if (!section->va)
> +		return false;
> +
> +	section->pa = addr;
> +	spin_lock_init(&section->lock);
> +	INIT_LIST_HEAD(&section->page_list);
> +	INIT_LIST_HEAD(&section->unsanitized_page_list);
> +
> +	for (i = 0; i < nr_pages; i++) {
> +		page = kzalloc(sizeof(*page), GFP_KERNEL);
> +		if (!page)
> +			goto err_out;
> +
> +		page->desc = (addr + (i << PAGE_SHIFT)) | index;
> +		list_add_tail(&page->list, &section->unsanitized_page_list);
> +	}
> +
> +	return true;
> +
> +err_out:
> +	sgx_free_epc_section(section);
> +	return false;
> +}
> +
> +static void __init sgx_page_cache_teardown(void)
> +{
> +	int i;
> +
> +	for (i = 0; i < sgx_nr_epc_sections; i++)
> +		sgx_free_epc_section(&sgx_epc_sections[i]);
> +}
> +
> +/**
> + * A section metric is concatenated in a way that @low bits 12-31 define the
> + * bits 12-31 of the metric and @high bits 0-19 define the bits 32-51 of the
> + * metric.
> + */
> +static inline u64 __init sgx_calc_section_metric(u64 low, u64 high)
> +{
> +	return (low & GENMASK_ULL(31, 12)) +
> +	       ((high & GENMASK_ULL(19, 0)) << 32);
> +}
> +
> +static bool __init sgx_page_cache_init(void)
> +{
> +	u32 eax, ebx, ecx, edx, type;
> +	u64 pa, size;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(sgx_epc_sections); i++) {
> +		cpuid_count(SGX_CPUID, i + SGX_CPUID_FIRST_VARIABLE_SUB_LEAF,
> +			    &eax, &ebx, &ecx, &edx);
> +
> +		type = eax & SGX_CPUID_SUB_LEAF_TYPE_MASK;
> +		if (type == SGX_CPUID_SUB_LEAF_INVALID)
> +			break;
> +
> +		if (type != SGX_CPUID_SUB_LEAF_EPC_SECTION) {
> +			pr_err_once("Unknown EPC section type: %u\n", type);
> +			break;
> +		}
> +
> +		pa = sgx_calc_section_metric(eax, ebx);
> +		size = sgx_calc_section_metric(ecx, edx);
> +
> +		pr_info("EPC section 0x%llx-0x%llx\n", pa, pa + size - 1);
> +
> +		if (!sgx_setup_epc_section(pa, size, i, &sgx_epc_sections[i])) {
> +			pr_err("No free memory for an EPC section\n");
> +			break;
> +		}
> +
> +		sgx_nr_epc_sections++;
> +	}
> +
> +	if (!sgx_nr_epc_sections) {
> +		pr_err("There are zero EPC sections.\n");
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +static void __init sgx_init(void)
> +{
> +	if (!boot_cpu_has(X86_FEATURE_SGX))
> +		return;
> +
> +	if (!sgx_page_cache_init())
> +		return;
> +
> +	if (!sgx_page_reclaimer_init())
> +		goto err_page_cache;
> +
> +	return;
> +
> +err_page_cache:
> +	sgx_page_cache_teardown();
> +}
> +
> +device_initcall(sgx_init);
> diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
> new file mode 100644
> index 000000000000..dff4f5f16d09
> --- /dev/null
> +++ b/arch/x86/kernel/cpu/sgx/sgx.h
> @@ -0,0 +1,52 @@
> +/* SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause) */
> +#ifndef _X86_SGX_H
> +#define _X86_SGX_H
> +
> +#include <linux/bitops.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/rwsem.h>
> +#include <linux/types.h>
> +#include <asm/asm.h>
> +#include "arch.h"
> +
> +#undef pr_fmt
> +#define pr_fmt(fmt) "sgx: " fmt
> +
> +struct sgx_epc_page {
> +	unsigned long desc;
> +	struct list_head list;
> +};
> +
> +/*
> + * The firmware can define multiple chunks of EPC to the different areas of the
> + * physical memory e.g. for memory areas of the each node. This structure is
> + * used to store EPC pages for one EPC section and virtual memory area where
> + * the pages have been mapped.
> + */
> +struct sgx_epc_section {
> +	unsigned long pa;
> +	void *va;
> +	struct list_head page_list;
> +	struct list_head unsanitized_page_list;
> +	spinlock_t lock;
> +};
> +
> +#define SGX_EPC_SECTION_MASK		GENMASK(7, 0)
> +#define SGX_MAX_EPC_SECTIONS		(SGX_EPC_SECTION_MASK + 1)
> +
> +extern struct sgx_epc_section sgx_epc_sections[SGX_MAX_EPC_SECTIONS];
> +
> +static inline struct sgx_epc_section *sgx_get_epc_section(struct sgx_epc_page *page)
> +{
> +	return &sgx_epc_sections[page->desc & SGX_EPC_SECTION_MASK];
> +}
> +
> +static inline void *sgx_get_epc_addr(struct sgx_epc_page *page)
> +{
> +	struct sgx_epc_section *section = sgx_get_epc_section(page);
> +
> +	return section->va + (page->desc & PAGE_MASK) - section->pa;
> +}
> +
> +#endif /* _X86_SGX_H */
> -- 
> 2.25.1