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[kvm-devel] [3/3] -reserved-ram for PCI passthrough without iommu and without paravirt
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From: Andrea A. <an...@qu...> - 2008-03-31 17:21:05
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Hello, The "reserved RAM" can be mapped by virtualization software with /dev/mem to create a 1:1 mapping between guest physical (bus) address and host physical (bus) address. Please let me know if something like this can be merged in -mm (this is the minimal possible change to achieve the feature). The part at the end is more a fix, but it's only required with this applied (unless you want to have a kexec above ~40M). Here the complete patchset: http://marc.info/?l=kvm-devel&m=120698256716369&w=2 http://marc.info/?l=kvm-devel&m=120698299317253&w=2 http://marc.info/?l=kvm-devel&m=120698328617835&w=2 Note current mainline is buggy so this patch should also applied with -R for the host kernel to boot but hopefully the regression will be solved sooner than later (no reply yet though). http://marc.info/?l=kvm-devel&m=120673375913890&w=2 andrea@svm ~ $ cat /proc/iomem | head 00000000-00000fff : reserved RAM failed 00001000-0008ffff : reserved RAM 00090000-00091fff : reserved RAM failed 00092000-0009efff : reserved RAM 0009f000-0009ffff : reserved 000cd600-000cffff : pnp 00:0d 000f0000-000fffff : reserved 00100000-1fffffff : reserved RAM 20000000-3dedffff : System RAM Signed-off-by: Andrea Arcangeli <an...@qu...> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1107,8 +1107,36 @@ config CRASH_DUMP (CONFIG_RELOCATABLE=y). For more details see Documentation/kdump/kdump.txt +config RESERVE_PHYSICAL_START + bool "Reserve all RAM below PHYSICAL_START (EXPERIMENTAL)" + depends on !RELOCATABLE && X86_64 + help + This makes the kernel use only RAM above __PHYSICAL_START. + All memory below __PHYSICAL_START will be left unused and + marked as "reserved RAM" in /proc/iomem. The few special + pages that can't be relocated at addresses above + __PHYSICAL_START and that can't be guaranteed to be unused + by the running kernel will be marked "reserved RAM failed" + in /proc/iomem. Those may or may be not used by the kernel + (for example SMP trampoline pages would only be used if + CPU hotplug is enabled). + + The "reserved RAM" can be mapped by virtualization software + with /dev/mem to create a 1:1 mapping between guest physical + (bus) address and host physical (bus) address. This will + allow PCI passthrough with DMA for the guest using the RAM + with the 1:1 mapping. The only detail to take care of is the + RAM marked "reserved RAM failed". The virtualization + software must create for the guest an e820 map that only + includes the "reserved RAM" regions but if the guest touches + memory with guest physical address in the "reserved RAM + failed" ranges (Linux guest will do that even if the RAM + isn't present in the e820 map), it should provide that as + RAM and map it with a non-linear mapping. This should allow + any Linux kernel to run fine and hopefully any other OS too. + config PHYSICAL_START - hex "Physical address where the kernel is loaded" if (EMBEDDED || CRASH_DUMP) + hex "Physical address where the kernel is loaded" if (EMBEDDED || CRASH_DUMP || RESERVE_PHYSICAL_START) default "0x1000000" if X86_NUMAQ default "0x200000" if X86_64 default "0x100000" diff --git a/arch/x86/kernel/e820_64.c b/arch/x86/kernel/e820_64.c --- a/arch/x86/kernel/e820_64.c +++ b/arch/x86/kernel/e820_64.c @@ -91,6 +91,11 @@ void __init early_res_to_bootmem(void) printk(KERN_INFO "early res: %d [%lx-%lx] %s\n", i, r->start, r->end - 1, r->name); reserve_bootmem_generic(r->start, r->end - r->start); +#ifdef CONFIG_RESERVE_PHYSICAL_START + if (r->start < __PHYSICAL_START) + add_memory_region(r->start, r->end - r->start, + E820_RESERVED_RAM_FAILED); +#endif } } @@ -231,6 +236,10 @@ void __init e820_reserve_resources(struc struct resource *data_resource, struct resource *bss_resource) { int i; +#ifdef CONFIG_RESERVE_PHYSICAL_START + /* solve E820_RESERVED_RAM vs E820_RESERVED_RAM_FAILED conflicts */ + update_e820(); +#endif for (i = 0; i < e820.nr_map; i++) { struct resource *res; res = alloc_bootmem_low(sizeof(struct resource)); @@ -238,6 +247,16 @@ void __init e820_reserve_resources(struc case E820_RAM: res->name = "System RAM"; break; case E820_ACPI: res->name = "ACPI Tables"; break; case E820_NVS: res->name = "ACPI Non-volatile Storage"; break; +#ifdef CONFIG_RESERVE_PHYSICAL_START + case E820_RESERVED_RAM_FAILED: + res->name = "reserved RAM failed"; + break; + case E820_RESERVED_RAM: + memset(__va(e820.map[i].addr), + POISON_FREE_INITMEM, e820.map[i].size); + res->name = "reserved RAM"; + break; +#endif default: res->name = "reserved"; } res->start = e820.map[i].addr; @@ -410,6 +429,14 @@ static void __init e820_print_map(char * case E820_NVS: printk(KERN_CONT "(ACPI NVS)\n"); break; +#ifdef CONFIG_RESERVE_PHYSICAL_START + case E820_RESERVED_RAM: + printk(KERN_CONT "(reserved RAM)\n"); + break; + case E820_RESERVED_RAM_FAILED: + printk(KERN_CONT "(reserved RAM failed)\n"); + break; +#endif default: printk(KERN_CONT "type %u\n", e820.map[i].type); break; @@ -639,9 +666,31 @@ static int __init copy_e820_map(struct e unsigned long end = start + size; unsigned long type = biosmap->type; +#ifdef CONFIG_RESERVE_PHYSICAL_START + /* make space for two more low-prio types */ + type += 2; +#endif + /* Overflow in 64 bits? Ignore the memory map. */ if (start > end) return -1; + +#ifdef CONFIG_RESERVE_PHYSICAL_START + if (type == E820_RAM) { + if (end <= __PHYSICAL_START) { + add_memory_region(start, size, + E820_RESERVED_RAM); + continue; + } + if (start < __PHYSICAL_START) { + add_memory_region(start, + __PHYSICAL_START-start, + E820_RESERVED_RAM); + size -= __PHYSICAL_START-start; + start = __PHYSICAL_START; + } + } +#endif add_memory_region(start, size, type); } while (biosmap++, --nr_map); diff --git a/include/asm-x86/e820.h b/include/asm-x86/e820.h --- a/include/asm-x86/e820.h +++ b/include/asm-x86/e820.h @@ -4,10 +4,19 @@ #define E820MAX 128 /* number of entries in E820MAP */ #define E820NR 0x1e8 /* # entries in E820MAP */ +#ifdef CONFIG_RESERVE_PHYSICAL_START +#define E820_RESERVED_RAM 1 +#define E820_RESERVED_RAM_FAILED 2 +#define E820_RAM 3 +#define E820_RESERVED 4 +#define E820_ACPI 5 +#define E820_NVS 6 +#else #define E820_RAM 1 #define E820_RESERVED 2 #define E820_ACPI 3 #define E820_NVS 4 +#endif #ifndef __ASSEMBLY__ struct e820entry { diff --git a/include/asm-x86/page_64.h b/include/asm-x86/page_64.h --- a/include/asm-x86/page_64.h +++ b/include/asm-x86/page_64.h @@ -29,6 +29,7 @@ #define __PAGE_OFFSET _AC(0xffff810000000000, UL) #define __PHYSICAL_START CONFIG_PHYSICAL_START +#define __PHYSICAL_OFFSET (__PHYSICAL_START-0x200000) #define __KERNEL_ALIGN 0x200000 /* @@ -51,7 +52,7 @@ * Kernel image size is limited to 128 MB (see level2_kernel_pgt in * arch/x86/kernel/head_64.S), and it is mapped here: */ -#define KERNEL_IMAGE_SIZE (128*1024*1024) +#define KERNEL_IMAGE_SIZE (128*1024*1024+__PHYSICAL_OFFSET) #define KERNEL_IMAGE_START _AC(0xffffffff80000000, UL) #ifndef __ASSEMBLY__ diff --git a/include/asm-x86/pgtable_64.h b/include/asm-x86/pgtable_64.h --- a/include/asm-x86/pgtable_64.h +++ b/include/asm-x86/pgtable_64.h @@ -140,7 +140,7 @@ static inline void native_pgd_clear(pgd_ #define VMALLOC_START _AC(0xffffc20000000000, UL) #define VMALLOC_END _AC(0xffffe1ffffffffff, UL) #define VMEMMAP_START _AC(0xffffe20000000000, UL) -#define MODULES_VADDR _AC(0xffffffff88000000, UL) +#define MODULES_VADDR (0xffffffff88000000UL+__PHYSICAL_OFFSET) #define MODULES_END _AC(0xfffffffffff00000, UL) #define MODULES_LEN (MODULES_END - MODULES_VADDR) diff --git a/include/asm-x86/smp_64.h b/include/asm-x86/smp_64.h --- a/include/asm-x86/smp_64.h +++ b/include/asm-x86/smp_64.h @@ -47,7 +47,11 @@ static inline int cpu_present_to_apicid( #ifdef CONFIG_SMP +#ifndef CONFIG_RESERVE_PHYSICAL_START #define SMP_TRAMPOLINE_BASE 0x6000 +#else +#define SMP_TRAMPOLINE_BASE 0x90000 /* move it next to 640k */ +#endif extern int __cpu_disable(void); extern void __cpu_die(unsigned int cpu); |
