| Message ID | 20180612143915.68065-15-kirill.shutemov@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 12.06.2018 17:39, Kirill A. Shutemov wrote: > Kernel need to have a way to access encrypted memory. We are going to > use per-KeyID direct mapping to facilitate the access with minimal > overhead. > > Direct mapping for each KeyID will be put next to each other in the > virtual address space. We need to have a way to find boundaries of > direct mapping for particular KeyID. > > The new variable direct_mapping_size specifies the size of direct > mapping. With the value, it's trivial to find direct mapping for > KeyID-N: PAGE_OFFSET + N * direct_mapping_size. > > Size of direct mapping is calculated during KASLR setup. If KALSR is > disable it happens during MKTME initialization. > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > --- > arch/x86/include/asm/mktme.h | 2 ++ > arch/x86/include/asm/page_64.h | 1 + > arch/x86/kernel/head64.c | 2 ++ > arch/x86/mm/kaslr.c | 21 ++++++++++++--- > arch/x86/mm/mktme.c | 48 ++++++++++++++++++++++++++++++++++ > 5 files changed, 71 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/include/asm/mktme.h b/arch/x86/include/asm/mktme.h > index 9363b989a021..3bf481fe3f56 100644 > --- a/arch/x86/include/asm/mktme.h > +++ b/arch/x86/include/asm/mktme.h > @@ -40,6 +40,8 @@ int page_keyid(const struct page *page); > > void mktme_disable(void); > > +void setup_direct_mapping_size(void); > + > #else > #define mktme_keyid_mask ((phys_addr_t)0) > #define mktme_nr_keyids 0 > diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h > index 939b1cff4a7b..53c32af895ab 100644 > --- a/arch/x86/include/asm/page_64.h > +++ b/arch/x86/include/asm/page_64.h > @@ -14,6 +14,7 @@ extern unsigned long phys_base; > extern unsigned long page_offset_base; > extern unsigned long vmalloc_base; > extern unsigned long vmemmap_base; > +extern unsigned long direct_mapping_size; > > static inline unsigned long __phys_addr_nodebug(unsigned long x) > { > diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c > index a21d6ace648e..b6175376b2e1 100644 > --- a/arch/x86/kernel/head64.c > +++ b/arch/x86/kernel/head64.c > @@ -59,6 +59,8 @@ EXPORT_SYMBOL(vmalloc_base); > unsigned long vmemmap_base __ro_after_init = __VMEMMAP_BASE_L4; > EXPORT_SYMBOL(vmemmap_base); > #endif > +unsigned long direct_mapping_size __ro_after_init = -1UL; > +EXPORT_SYMBOL(direct_mapping_size); > > #define __head __section(.head.text) > > diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c > index 4408cd9a3bef..3d8ef8cb97e1 100644 > --- a/arch/x86/mm/kaslr.c > +++ b/arch/x86/mm/kaslr.c > @@ -69,6 +69,15 @@ static inline bool kaslr_memory_enabled(void) > return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN); > } > > +#ifndef CONFIG_X86_INTEL_MKTME > +static void __init setup_direct_mapping_size(void) > +{ > + direct_mapping_size = max_pfn << PAGE_SHIFT; > + direct_mapping_size = round_up(direct_mapping_size, 1UL << TB_SHIFT); > + direct_mapping_size += (1UL << TB_SHIFT) * CONFIG_MEMORY_PHYSICAL_PADDING; > +} > +#endif > + > /* Initialize base and padding for each memory region randomized with KASLR */ > void __init kernel_randomize_memory(void) > { > @@ -93,7 +102,11 @@ void __init kernel_randomize_memory(void) > if (!kaslr_memory_enabled()) > return; > > - kaslr_regions[0].size_tb = 1 << (__PHYSICAL_MASK_SHIFT - TB_SHIFT); > + /* > + * Upper limit for direct mapping size is 1/4 of whole virtual > + * address space or 1/2? > + */ > + kaslr_regions[0].size_tb = 1 << (__VIRTUAL_MASK_SHIFT - 1 - TB_SHIFT); > kaslr_regions[1].size_tb = VMALLOC_SIZE_TB; > > /* > @@ -101,8 +114,10 @@ void __init kernel_randomize_memory(void) > * add padding if needed (especially for memory hotplug support). > */ > BUG_ON(kaslr_regions[0].base != &page_offset_base); > - memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) + > - CONFIG_MEMORY_PHYSICAL_PADDING; > + > + setup_direct_mapping_size(); > + > + memory_tb = direct_mapping_size * mktme_nr_keyids + 1; parenthesis ? memory_tb = direct_mapping_size * (mktme_nr_keyids + 1); > > /* Adapt phyiscal memory region size based on available memory */ > if (memory_tb < kaslr_regions[0].size_tb) > diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c > index 43a44f0f2a2d..3e5322bf035e 100644 > --- a/arch/x86/mm/mktme.c > +++ b/arch/x86/mm/mktme.c > @@ -89,3 +89,51 @@ static bool need_page_mktme(void) > struct page_ext_operations page_mktme_ops = { > .need = need_page_mktme, > }; > + > +void __init setup_direct_mapping_size(void) > +{ > + unsigned long available_va; > + > + /* 1/4 of virtual address space is didicated for direct mapping */ > + available_va = 1UL << (__VIRTUAL_MASK_SHIFT - 1); > + > + /* How much memory the systrem has? */ > + direct_mapping_size = max_pfn << PAGE_SHIFT; > + direct_mapping_size = round_up(direct_mapping_size, 1UL << 40); > + > + if (mktme_status != MKTME_ENUMERATED) > + goto out; > + > + /* > + * Not enough virtual address space to address all physical memory with > + * MKTME enabled. Even without padding. > + * > + * Disable MKTME instead. > + */ > + if (direct_mapping_size > available_va / mktme_nr_keyids + 1) { parenthesis again? if (direct_mapping_size > available_va / (mktme_nr_keyids + 1)) { > + pr_err("x86/mktme: Disabled. Not enough virtual address space\n"); > + pr_err("x86/mktme: Consider switching to 5-level paging\n"); > + mktme_disable(); > + goto out; > + } > + > + /* > + * Virtual address space is divided between per-KeyID direct mappings. > + */ > + available_va /= mktme_nr_keyids + 1 > +out: > + /* Add padding, if there's enough virtual address space */ > + direct_mapping_size += (1UL << 40) * CONFIG_MEMORY_PHYSICAL_PADDING; > + if (direct_mapping_size > available_va) > + direct_mapping_size = available_va; > +} > + > +static int __init mktme_init(void) > +{ > + /* KASLR didn't initialized it for us. */ > + if (direct_mapping_size == -1UL) > + setup_direct_mapping_size(); > + > + return 0; > +} > +arch_initcall(mktme_init)
On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote: > Kernel need to have a way to access encrypted memory. We are going to "The kernel needs"... > use per-KeyID direct mapping to facilitate the access with minimal > overhead. What are the security implications of this approach? > Direct mapping for each KeyID will be put next to each other in the That needs to be "a direct mapping" or "the direct mapping". It's missing an article to start the sentence. > virtual address space. We need to have a way to find boundaries of > direct mapping for particular KeyID. > > The new variable direct_mapping_size specifies the size of direct > mapping. With the value, it's trivial to find direct mapping for > KeyID-N: PAGE_OFFSET + N * direct_mapping_size. I think this deserves an update to Documentation/x86/x86_64/mm.txt, no? > Size of direct mapping is calculated during KASLR setup. If KALSR is > disable it happens during MKTME initialization. "disabled" > diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c > index 4408cd9a3bef..3d8ef8cb97e1 100644 > --- a/arch/x86/mm/kaslr.c > +++ b/arch/x86/mm/kaslr.c > @@ -69,6 +69,15 @@ static inline bool kaslr_memory_enabled(void) > return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN); > } > > +#ifndef CONFIG_X86_INTEL_MKTME > +static void __init setup_direct_mapping_size(void) > +{ > + direct_mapping_size = max_pfn << PAGE_SHIFT; > + direct_mapping_size = round_up(direct_mapping_size, 1UL << TB_SHIFT); > + direct_mapping_size += (1UL << TB_SHIFT) * CONFIG_MEMORY_PHYSICAL_PADDING; > +} > +#endif Comments, please. > /* Initialize base and padding for each memory region randomized with KASLR */ > void __init kernel_randomize_memory(void) > { > @@ -93,7 +102,11 @@ void __init kernel_randomize_memory(void) > if (!kaslr_memory_enabled()) > return; > > - kaslr_regions[0].size_tb = 1 << (__PHYSICAL_MASK_SHIFT - TB_SHIFT); > + /* > + * Upper limit for direct mapping size is 1/4 of whole virtual > + * address space > + */ > + kaslr_regions[0].size_tb = 1 << (__VIRTUAL_MASK_SHIFT - 1 - TB_SHIFT); Is this a cleanup that can be separate? > kaslr_regions[1].size_tb = VMALLOC_SIZE_TB; > > /* > @@ -101,8 +114,10 @@ void __init kernel_randomize_memory(void) > * add padding if needed (especially for memory hotplug support). > */ > BUG_ON(kaslr_regions[0].base != &page_offset_base); > - memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) + > - CONFIG_MEMORY_PHYSICAL_PADDING; > + > + setup_direct_mapping_size(); > + > + memory_tb = direct_mapping_size * mktme_nr_keyids + 1; What's the +1 for? Is "mktme_nr_keyids" 0 for "MKTME unsupported"? That needs to be called out, I think. > /* Adapt phyiscal memory region size based on available memory */ > if (memory_tb < kaslr_regions[0].size_tb) > diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c > index 43a44f0f2a2d..3e5322bf035e 100644 > --- a/arch/x86/mm/mktme.c > +++ b/arch/x86/mm/mktme.c > @@ -89,3 +89,51 @@ static bool need_page_mktme(void) > struct page_ext_operations page_mktme_ops = { > .need = need_page_mktme, > }; > + > +void __init setup_direct_mapping_size(void) > +{ > + unsigned long available_va; > + > + /* 1/4 of virtual address space is didicated for direct mapping */ > + available_va = 1UL << (__VIRTUAL_MASK_SHIFT - 1); > + > + /* How much memory the systrem has? */ > + direct_mapping_size = max_pfn << PAGE_SHIFT; > + direct_mapping_size = round_up(direct_mapping_size, 1UL << 40); > + > + if (mktme_status != MKTME_ENUMERATED) > + goto out; > + > + /* > + * Not enough virtual address space to address all physical memory with > + * MKTME enabled. Even without padding. > + * > + * Disable MKTME instead. > + */ > + if (direct_mapping_size > available_va / mktme_nr_keyids + 1) { > + pr_err("x86/mktme: Disabled. Not enough virtual address space\n"); > + pr_err("x86/mktme: Consider switching to 5-level paging\n"); > + mktme_disable(); > + goto out; > + } > + > + /* > + * Virtual address space is divided between per-KeyID direct mappings. > + */ > + available_va /= mktme_nr_keyids + 1; > +out: > + /* Add padding, if there's enough virtual address space */ > + direct_mapping_size += (1UL << 40) * CONFIG_MEMORY_PHYSICAL_PADDING; > + if (direct_mapping_size > available_va) > + direct_mapping_size = available_va; > +} Do you really need two copies of this function? Shouldn't it see mktme_status!=MKTME_ENUMERATED and just jump out? How is the code before that "goto out" different from the CONFIG_MKTME=n case?
On Wed, Jun 13, 2018 at 06:37:07PM +0000, Dave Hansen wrote: > On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote: > > Kernel need to have a way to access encrypted memory. We are going to > "The kernel needs"... > > > use per-KeyID direct mapping to facilitate the access with minimal > > overhead. > > What are the security implications of this approach? I'll add this to the message: Per-KeyID mappings require a lot more virtual address space. On 4-level machine with 64 KeyIDs we max out 46-bit virtual address space dedicated for direct mapping with 1TiB of RAM. Given that we round up any calculation on direct mapping size to 1TiB, we effectively claim all 46-bit address space for direct mapping on such machine regardless of RAM size. Increased usage of virtual address space has implications for KASLR: we have less space for randomization. With 64 TiB claimed for direct mapping with 4-level we left with 27 TiB of entropy to place page_offset_base, vmalloc_base and vmemmap_base. 5-level paging provides much wider virtual address space and KASLR doesn't suffer significantly from per-KeyID direct mappings. It's preferred to run MKTME with 5-level paging. > > Direct mapping for each KeyID will be put next to each other in the > > That needs to be "a direct mapping" or "the direct mapping". It's > missing an article to start the sentence. Okay. > > virtual address space. We need to have a way to find boundaries of > > direct mapping for particular KeyID. > > > > The new variable direct_mapping_size specifies the size of direct > > mapping. With the value, it's trivial to find direct mapping for > > KeyID-N: PAGE_OFFSET + N * direct_mapping_size. > > I think this deserves an update to Documentation/x86/x86_64/mm.txt, no? Right, I'll update it. > > Size of direct mapping is calculated during KASLR setup. If KALSR is > > disable it happens during MKTME initialization. > > "disabled" > > > diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c > > index 4408cd9a3bef..3d8ef8cb97e1 100644 > > --- a/arch/x86/mm/kaslr.c > > +++ b/arch/x86/mm/kaslr.c > > @@ -69,6 +69,15 @@ static inline bool kaslr_memory_enabled(void) > > return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN); > > } > > > > +#ifndef CONFIG_X86_INTEL_MKTME > > +static void __init setup_direct_mapping_size(void) > > +{ > > + direct_mapping_size = max_pfn << PAGE_SHIFT; > > + direct_mapping_size = round_up(direct_mapping_size, 1UL << TB_SHIFT); > > + direct_mapping_size += (1UL << TB_SHIFT) * CONFIG_MEMORY_PHYSICAL_PADDING; > > +} > > +#endif > > Comments, please. Okay. > > /* Initialize base and padding for each memory region randomized with KASLR */ > > void __init kernel_randomize_memory(void) > > { > > @@ -93,7 +102,11 @@ void __init kernel_randomize_memory(void) > > if (!kaslr_memory_enabled()) > > return; > > > > - kaslr_regions[0].size_tb = 1 << (__PHYSICAL_MASK_SHIFT - TB_SHIFT); > > + /* > > + * Upper limit for direct mapping size is 1/4 of whole virtual > > + * address space > > + */ > > + kaslr_regions[0].size_tb = 1 << (__VIRTUAL_MASK_SHIFT - 1 - TB_SHIFT); > > Is this a cleanup that can be separate? Right. I'll split it up. > > kaslr_regions[1].size_tb = VMALLOC_SIZE_TB; > > > > /* > > @@ -101,8 +114,10 @@ void __init kernel_randomize_memory(void) > > * add padding if needed (especially for memory hotplug support). > > */ > > BUG_ON(kaslr_regions[0].base != &page_offset_base); > > - memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) + > > - CONFIG_MEMORY_PHYSICAL_PADDING; > > + > > + setup_direct_mapping_size(); > > + > > + memory_tb = direct_mapping_size * mktme_nr_keyids + 1; > > What's the +1 for? Is "mktme_nr_keyids" 0 for "MKTME unsupported"? > That needs to be called out, I think. I'll add a comment. > > /* Adapt phyiscal memory region size based on available memory */ > > if (memory_tb < kaslr_regions[0].size_tb) > > diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c > > index 43a44f0f2a2d..3e5322bf035e 100644 > > --- a/arch/x86/mm/mktme.c > > +++ b/arch/x86/mm/mktme.c > > @@ -89,3 +89,51 @@ static bool need_page_mktme(void) > > struct page_ext_operations page_mktme_ops = { > > .need = need_page_mktme, > > }; > > + > > +void __init setup_direct_mapping_size(void) > > +{ > > + unsigned long available_va; > > + > > + /* 1/4 of virtual address space is didicated for direct mapping */ > > + available_va = 1UL << (__VIRTUAL_MASK_SHIFT - 1); > > + > > + /* How much memory the systrem has? */ > > + direct_mapping_size = max_pfn << PAGE_SHIFT; > > + direct_mapping_size = round_up(direct_mapping_size, 1UL << 40); > > + > > + if (mktme_status != MKTME_ENUMERATED) > > + goto out; > > + > > + /* > > + * Not enough virtual address space to address all physical memory with > > + * MKTME enabled. Even without padding. > > + * > > + * Disable MKTME instead. > > + */ > > + if (direct_mapping_size > available_va / mktme_nr_keyids + 1) { > > + pr_err("x86/mktme: Disabled. Not enough virtual address space\n"); > > + pr_err("x86/mktme: Consider switching to 5-level paging\n"); > > + mktme_disable(); > > + goto out; > > + } > > + > > + /* > > + * Virtual address space is divided between per-KeyID direct mappings. > > + */ > > + available_va /= mktme_nr_keyids + 1; > > +out: > > + /* Add padding, if there's enough virtual address space */ > > + direct_mapping_size += (1UL << 40) * CONFIG_MEMORY_PHYSICAL_PADDING; > > + if (direct_mapping_size > available_va) > > + direct_mapping_size = available_va; > > +} > > Do you really need two copies of this function? Shouldn't it see > mktme_status!=MKTME_ENUMERATED and just jump out? How is the code > before that "goto out" different from the CONFIG_MKTME=n case? mktme.c is not compiled for CONFIG_MKTME=n.
On 06/18/2018 06:12 AM, Kirill A. Shutemov wrote: > On Wed, Jun 13, 2018 at 06:37:07PM +0000, Dave Hansen wrote: >> On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote: >>> Kernel need to have a way to access encrypted memory. We are going to >> "The kernel needs"... >> >>> use per-KeyID direct mapping to facilitate the access with minimal >>> overhead. >> >> What are the security implications of this approach? > > I'll add this to the message: > > Per-KeyID mappings require a lot more virtual address space. On 4-level > machine with 64 KeyIDs we max out 46-bit virtual address space dedicated > for direct mapping with 1TiB of RAM. Given that we round up any > calculation on direct mapping size to 1TiB, we effectively claim all > 46-bit address space for direct mapping on such machine regardless of > RAM size. ... I was thinking more in terms of the exposure of keeping the plaintext mapped all the time. Imagine Meltdown if the decrypted page is not mapped into the kernel: this feature could actually have protected user data. But, with this scheme, it exposes the data... all the data... with all possible keys... all the time. That's one heck of an attack surface. Can we do better? >>> struct page_ext_operations page_mktme_ops = { >>> .need = need_page_mktme, >>> }; >>> + >>> +void __init setup_direct_mapping_size(void) >>> +{ ... >>> +} >> >> Do you really need two copies of this function? Shouldn't it see >> mktme_status!=MKTME_ENUMERATED and just jump out? How is the code >> before that "goto out" different from the CONFIG_MKTME=n case? > > mktme.c is not compiled for CONFIG_MKTME=n. I'd rather have one copy in shared code which is mosty optimized away when CONFIG_MKTME=n than two copies.
diff --git a/arch/x86/include/asm/mktme.h b/arch/x86/include/asm/mktme.h index 9363b989a021..3bf481fe3f56 100644 --- a/arch/x86/include/asm/mktme.h +++ b/arch/x86/include/asm/mktme.h @@ -40,6 +40,8 @@ int page_keyid(const struct page *page); void mktme_disable(void); +void setup_direct_mapping_size(void); + #else #define mktme_keyid_mask ((phys_addr_t)0) #define mktme_nr_keyids 0 diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h index 939b1cff4a7b..53c32af895ab 100644 --- a/arch/x86/include/asm/page_64.h +++ b/arch/x86/include/asm/page_64.h @@ -14,6 +14,7 @@ extern unsigned long phys_base; extern unsigned long page_offset_base; extern unsigned long vmalloc_base; extern unsigned long vmemmap_base; +extern unsigned long direct_mapping_size; static inline unsigned long __phys_addr_nodebug(unsigned long x) { diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index a21d6ace648e..b6175376b2e1 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -59,6 +59,8 @@ EXPORT_SYMBOL(vmalloc_base); unsigned long vmemmap_base __ro_after_init = __VMEMMAP_BASE_L4; EXPORT_SYMBOL(vmemmap_base); #endif +unsigned long direct_mapping_size __ro_after_init = -1UL; +EXPORT_SYMBOL(direct_mapping_size); #define __head __section(.head.text) diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index 4408cd9a3bef..3d8ef8cb97e1 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -69,6 +69,15 @@ static inline bool kaslr_memory_enabled(void) return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN); } +#ifndef CONFIG_X86_INTEL_MKTME +static void __init setup_direct_mapping_size(void) +{ + direct_mapping_size = max_pfn << PAGE_SHIFT; + direct_mapping_size = round_up(direct_mapping_size, 1UL << TB_SHIFT); + direct_mapping_size += (1UL << TB_SHIFT) * CONFIG_MEMORY_PHYSICAL_PADDING; +} +#endif + /* Initialize base and padding for each memory region randomized with KASLR */ void __init kernel_randomize_memory(void) { @@ -93,7 +102,11 @@ void __init kernel_randomize_memory(void) if (!kaslr_memory_enabled()) return; - kaslr_regions[0].size_tb = 1 << (__PHYSICAL_MASK_SHIFT - TB_SHIFT); + /* + * Upper limit for direct mapping size is 1/4 of whole virtual + * address space + */ + kaslr_regions[0].size_tb = 1 << (__VIRTUAL_MASK_SHIFT - 1 - TB_SHIFT); kaslr_regions[1].size_tb = VMALLOC_SIZE_TB; /* @@ -101,8 +114,10 @@ void __init kernel_randomize_memory(void) * add padding if needed (especially for memory hotplug support). */ BUG_ON(kaslr_regions[0].base != &page_offset_base); - memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) + - CONFIG_MEMORY_PHYSICAL_PADDING; + + setup_direct_mapping_size(); + + memory_tb = direct_mapping_size * mktme_nr_keyids + 1; /* Adapt phyiscal memory region size based on available memory */ if (memory_tb < kaslr_regions[0].size_tb) diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c index 43a44f0f2a2d..3e5322bf035e 100644 --- a/arch/x86/mm/mktme.c +++ b/arch/x86/mm/mktme.c @@ -89,3 +89,51 @@ static bool need_page_mktme(void) struct page_ext_operations page_mktme_ops = { .need = need_page_mktme, }; + +void __init setup_direct_mapping_size(void) +{ + unsigned long available_va; + + /* 1/4 of virtual address space is didicated for direct mapping */ + available_va = 1UL << (__VIRTUAL_MASK_SHIFT - 1); + + /* How much memory the systrem has? */ + direct_mapping_size = max_pfn << PAGE_SHIFT; + direct_mapping_size = round_up(direct_mapping_size, 1UL << 40); + + if (mktme_status != MKTME_ENUMERATED) + goto out; + + /* + * Not enough virtual address space to address all physical memory with + * MKTME enabled. Even without padding. + * + * Disable MKTME instead. + */ + if (direct_mapping_size > available_va / mktme_nr_keyids + 1) { + pr_err("x86/mktme: Disabled. Not enough virtual address space\n"); + pr_err("x86/mktme: Consider switching to 5-level paging\n"); + mktme_disable(); + goto out; + } + + /* + * Virtual address space is divided between per-KeyID direct mappings. + */ + available_va /= mktme_nr_keyids + 1; +out: + /* Add padding, if there's enough virtual address space */ + direct_mapping_size += (1UL << 40) * CONFIG_MEMORY_PHYSICAL_PADDING; + if (direct_mapping_size > available_va) + direct_mapping_size = available_va; +} + +static int __init mktme_init(void) +{ + /* KASLR didn't initialized it for us. */ + if (direct_mapping_size == -1UL) + setup_direct_mapping_size(); + + return 0; +} +arch_initcall(mktme_init)
Kernel need to have a way to access encrypted memory. We are going to use per-KeyID direct mapping to facilitate the access with minimal overhead. Direct mapping for each KeyID will be put next to each other in the virtual address space. We need to have a way to find boundaries of direct mapping for particular KeyID. The new variable direct_mapping_size specifies the size of direct mapping. With the value, it's trivial to find direct mapping for KeyID-N: PAGE_OFFSET + N * direct_mapping_size. Size of direct mapping is calculated during KASLR setup. If KALSR is disable it happens during MKTME initialization. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- arch/x86/include/asm/mktme.h | 2 ++ arch/x86/include/asm/page_64.h | 1 + arch/x86/kernel/head64.c | 2 ++ arch/x86/mm/kaslr.c | 21 ++++++++++++--- arch/x86/mm/mktme.c | 48 ++++++++++++++++++++++++++++++++++ 5 files changed, 71 insertions(+), 3 deletions(-)