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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v9 2/5] xen/riscv: introduce setup_initial_pages
On Thu, May 25, 2023 at 06:28:15PM +0300, Oleksii Kurochko wrote:
> The idea was taken from xvisor but the following changes
> were done:
> * Use only a minimal part of the code enough to enable MMU
> * rename {_}setup_initial_pagetables functions
> * add an argument for setup_initial_mapping to have
> an opportunity to make set PTE flags.
> * update setup_initial_pagetables function to map sections
> with correct PTE flags.
> * Rewrite enable_mmu() to C.
> * map linker addresses range to load addresses range without
> 1:1 mapping. It will be 1:1 only in case when
> load_start_addr is equal to linker_start_addr.
> * add safety checks such as:
> * Xen size is less than page size
> * linker addresses range doesn't overlap load addresses
> range
> * Rework macros {THIRD,SECOND,FIRST,ZEROETH}_{SHIFT,MASK}
> * change PTE_LEAF_DEFAULT to RW instead of RWX.
> * Remove phys_offset as it is not used now
> * Remove alignment of {map, pa}_start &= XEN_PT_LEVEL_MAP_MASK(0);
> in setup_inital_mapping() as they should be already aligned.
> Make a check that {map_pa}_start are aligned.
> * Remove clear_pagetables() as initial pagetables will be
> zeroed during bss initialization
> * Remove __attribute__((section(".entry")) for setup_initial_pagetables()
> as there is no such section in xen.lds.S
> * Update the argument of pte_is_valid() to "const pte_t *p"
> * Add check that Xen's load address is aligned at 4k boundary
> * Refactor setup_initial_pagetables() so it is mapping linker
> address range to load address range. After setup needed
> permissions for specific section ( such as .text, .rodata, etc )
> otherwise RW permission will be set by default.
> * Add function to check that requested SATP_MODE is supported
>
> Origin: git@xxxxxxxxxx:xvisor/xvisor.git 9be2fdd7
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> Changes in V9:
> - Add "Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>" to commit message.
> - Update macros VPN_MASK.
> - Remove double blank lines.
> ---
> Changes in V8:
> - Add parentheses for lvl in pt_index() macros.
> - introduce macros paddr_to_pfn() and pfn_to_paddr() and use them inside
> paddr_to_pte()/pte_to_paddr().
> - Remove "__" in sfence_vma() and add blanks inside the parentheses of
> asm volatile.
> - Parenthesize the two & against the || at the start of
> setup_initial_mapping()
> function.
> - Code style fixes.
> ---
> Changes in V7:
> - define CONFIG_PAGING_LEVELS=2 for SATP_MODE_SV32.
> - update switch_stack_and_jump macros(): add constraint 'X' for fn,
> memory clobber and wrap into do {} while ( false ).
> - add noreturn to definition of enable_mmu().
> - update pt_index() to "(pt_linear_offset(lvl, (va)) & VPN_MASK)".
> - expand macros pte_to_addr()/addr_to_pte() in paddr_to_pte() and
> pte_to_paddr() functions and after drop them.
> - remove inclusion of <asm/config.h>.
> - update commit message around definition of PGTBL_INITIAL_COUNT.
> - remove PGTBL_ENTRY_AMOUNT and use PAGETABLE_ENTRIES instead.
> - code style fixes
> - remove permission argument of setup_initial_mapping() function
> - remove calc_pgtbl_lvls_num() as it's not needed anymore after
> definition
> of CONFIG_PAGING_LEVELS.
> - introduce sfence_vma().
> - remove satp_mode argument from check_pgtbl_mode_support() and use
> RV_STAGE1_MODE directly instead.
> - change .align to .p2align.
> - drop inclusion of <asm/asm-offsets.h> from head.S. This change isn't
> necessary for the current patch series.
> ---
> Changes in V6:
> - move PAGE_SHIFT, PADDR_BITS to the top of page-bits.h
> - cast argument x of pte_to_addr() macros to paddr_t to avoid risk of
> overflow for RV32
> - update type of num_levels from 'unsigned long' to 'unsigned int'
> - define PGTBL_INITIAL_COUNT as ((CONFIG_PAGING_LEVELS - 1) + 1)
> - update type of permission arguments. changed it from 'unsgined long'
> to 'unsigned int'
> - fix code style
> - switch while 'loop' to 'for' loop
> - undef HANDLE_PGTBL
> - clean root page table after MMU is disabled in
> check_pgtbl_mode_support() function
> - align __bss_start properly
> - remove unnecesssary const for paddr_to_pte, pte_to_paddr,
> pte_is_valid functions
> - add switch_stack_and_jump macros and use it inside enable_mmu()
> before jump to
> cont_after_mmu_is_enabled() function
> ---
> Changes in V5:
> * Indent fields of pte_t struct
> * Rename addr_to_pte() and ppn_to_paddr() to match their content
> ---
> Changes in V4:
> * use GB() macros instead of defining SZ_1G
> * hardcode XEN_VIRT_START and add comment (ADDRESS_SPACE_END + 1 - GB(1))
> * remove unnecessary 'asm' word at the end of #error
> * encapsulate pte_t definition in a struct
> * rename addr_to_ppn() to ppn_to_paddr().
> * change type of paddr argument from const unsigned long to paddr_t
> * pte_to_paddr() update prototype.
> * calculate size of Xen binary based on an amount of page tables
> * use unsgined int instead of 'uint32_t' instead of uint32_t as
> their use isn't warranted.
> * remove extern of bss_{start,end} as they aren't used in mm.c anymore
> * fix code style
> * add argument for HANDLE_PGTBL macros instead of curr_lvl_num variable
> * make enable_mmu() as noinline to prevent under link-time optimization
> because of the nature of enable_mmu()
> * add function to check that SATP_MODE is supported.
> * update the commit message
> * update setup_initial_pagetables to set correct PTE flags in one pass
> instead of calling setup_pte_permissions after setup_initial_pagetables()
> as setup_initial_pagetables() isn't used to change permission flags.
> ---
> Changes in V3:
> - update definition of pte_t structure to have a proper size of pte_t
> in case of RV32.
> - update asm/mm.h with new functions and remove unnecessary 'extern'.
> - remove LEVEL_* macros as only XEN_PT_LEVEL_* are enough.
> - update paddr_to_pte() to receive permissions as an argument.
> - add check that map_start & pa_start is properly aligned.
> - move defines PAGETABLE_ORDER, PAGETABLE_ENTRIES, PTE_PPN_SHIFT to
> <asm/page-bits.h>
> - Rename PTE_SHIFT to PTE_PPN_SHIFT
> - refactor setup_initial_pagetables: map all LINK addresses to LOAD addresses
> and after setup PTEs permission for sections; update check that linker
> and load addresses don't overlap.
> - refactor setup_initial_mapping: allocate pagetable 'dynamically' if it is
> necessary.
> - rewrite enable_mmu in C; add the check that map_start and pa_start are
> aligned on 4k boundary.
> - update the comment for setup_initial_pagetable funcion
> - Add RV_STAGE1_MODE to support different MMU modes
> - set XEN_VIRT_START very high to not overlap with load address range
> - align bss section
> ---
> Changes in V2:
> * update the commit message:
> * Remove {ZEROETH,FIRST,...}_{SHIFT,MASK, SIZE,...} and
> introduce instead of them XEN_PT_LEVEL_*() and LEVEL_*
> * Rework pt_linear_offset() and pt_index based on XEN_PT_LEVEL_*()
> * Remove clear_pagetables() functions as pagetables were zeroed during
> .bss initialization
> * Rename _setup_initial_pagetables() to setup_initial_mapping()
> * Make PTE_DEFAULT equal to RX.
> * Update prototype of setup_initial_mapping(..., bool writable) ->
> setup_initial_mapping(..., UL flags)
> * Update calls of setup_initial_mapping according to new prototype
> * Remove unnecessary call of:
> _setup_initial_pagetables(..., load_addr_start, load_addr_end,
> load_addr_start, ...)
> * Define index* in the loop of setup_initial_mapping
> * Remove attribute "__attribute__((section(".entry")))" for
> setup_initial_pagetables()
> as we don't have such section
> * make arguments of paddr_to_pte() and pte_is_valid() as const.
> * make xen_second_pagetable static.
> * use <xen/kernel.h> instead of declaring extern unsigned long _stext,
> 0etext, _srodata, _erodata
> * update 'extern unsigned long __init_begin' to 'extern unsigned long
> __init_begin[]'
> * use aligned() instead of "__attribute__((__aligned__(PAGE_SIZE)))"
> * set __section(".bss.page_aligned") for page tables arrays
> * fix identatations
> * Change '__attribute__((section(".entry")))' to '__init'
> * Remove phys_offset as it isn't used now.
> * Remove alignment of {map, pa}_start &= XEN_PT_LEVEL_MAP_MASK(0); in
> setup_inital_mapping() as they should be already aligned.
> * Remove clear_pagetables() as initial pagetables will be
> zeroed during bss initialization
> * Remove __attribute__((section(".entry")) for setup_initial_pagetables()
> as there is no such section in xen.lds.S
> * Update the argument of pte_is_valid() to "const pte_t *p"
> ---
> xen/arch/riscv/Makefile | 1 +
> xen/arch/riscv/include/asm/config.h | 14 +-
> xen/arch/riscv/include/asm/current.h | 11 +
> xen/arch/riscv/include/asm/mm.h | 14 ++
> xen/arch/riscv/include/asm/page-bits.h | 10 +
> xen/arch/riscv/include/asm/page.h | 61 ++++++
> xen/arch/riscv/include/asm/processor.h | 5 +
> xen/arch/riscv/mm.c | 276 +++++++++++++++++++++++++
> xen/arch/riscv/setup.c | 11 +
> xen/arch/riscv/xen.lds.S | 3 +
> 10 files changed, 405 insertions(+), 1 deletion(-)
> create mode 100644 xen/arch/riscv/include/asm/current.h
> create mode 100644 xen/arch/riscv/include/asm/mm.h
> create mode 100644 xen/arch/riscv/include/asm/page.h
> create mode 100644 xen/arch/riscv/mm.c
>
> diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
> index 443f6bf15f..956ceb02df 100644
> --- a/xen/arch/riscv/Makefile
> +++ b/xen/arch/riscv/Makefile
> @@ -1,5 +1,6 @@
> obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
> obj-y += entry.o
> +obj-y += mm.o
> obj-$(CONFIG_RISCV_64) += riscv64/
> obj-y += sbi.o
> obj-y += setup.o
> diff --git a/xen/arch/riscv/include/asm/config.h
> b/xen/arch/riscv/include/asm/config.h
> index 9900d29dab..38862df0b8 100644
> --- a/xen/arch/riscv/include/asm/config.h
> +++ b/xen/arch/riscv/include/asm/config.h
> @@ -75,12 +75,24 @@
> name:
> #endif
>
> -#define XEN_VIRT_START _AT(UL, 0x80200000)
> +#ifdef CONFIG_RISCV_64
> +#define XEN_VIRT_START 0xFFFFFFFFC0000000 /* (_AC(-1, UL) + 1 - GB(1)) */
> +#else
> +#error "RV32 isn't supported"
> +#endif
>
> #define SMP_CACHE_BYTES (1 << 6)
>
> #define STACK_SIZE PAGE_SIZE
>
> +#ifdef CONFIG_RISCV_64
> +#define CONFIG_PAGING_LEVELS 3
> +#define RV_STAGE1_MODE SATP_MODE_SV39
> +#else
> +#define CONFIG_PAGING_LEVELS 2
> +#define RV_STAGE1_MODE SATP_MODE_SV32
> +#endif
> +
> #endif /* __RISCV_CONFIG_H__ */
> /*
> * Local variables:
> diff --git a/xen/arch/riscv/include/asm/current.h
> b/xen/arch/riscv/include/asm/current.h
> new file mode 100644
> index 0000000000..d87e6717e0
> --- /dev/null
> +++ b/xen/arch/riscv/include/asm/current.h
> @@ -0,0 +1,11 @@
> +#ifndef __ASM_CURRENT_H
> +#define __ASM_CURRENT_H
> +
> +#define switch_stack_and_jump(stack, fn) do { \
> + asm volatile ( \
> + "mv sp, %0\n" \
> + "j " #fn :: "r" (stack), "X" (fn) : "memory" ); \
> + unreachable(); \
> +} while ( false )
> +
> +#endif /* __ASM_CURRENT_H */
> diff --git a/xen/arch/riscv/include/asm/mm.h b/xen/arch/riscv/include/asm/mm.h
> new file mode 100644
> index 0000000000..64293eacee
> --- /dev/null
> +++ b/xen/arch/riscv/include/asm/mm.h
> @@ -0,0 +1,14 @@
> +#ifndef _ASM_RISCV_MM_H
> +#define _ASM_RISCV_MM_H
> +
> +#include <asm/page-bits.h>
> +
> +#define pfn_to_paddr(pfn) ((paddr_t)(pfn) << PAGE_SHIFT)
> +#define paddr_to_pfn(pa) ((unsigned long)((pa) >> PAGE_SHIFT))
> +
> +void setup_initial_pagetables(void);
> +
> +void enable_mmu(void);
> +void cont_after_mmu_is_enabled(void);
> +
> +#endif /* _ASM_RISCV_MM_H */
> diff --git a/xen/arch/riscv/include/asm/page-bits.h
> b/xen/arch/riscv/include/asm/page-bits.h
> index 1801820294..4a3e33589a 100644
> --- a/xen/arch/riscv/include/asm/page-bits.h
> +++ b/xen/arch/riscv/include/asm/page-bits.h
> @@ -4,4 +4,14 @@
> #define PAGE_SHIFT 12 /* 4 KiB Pages */
> #define PADDR_BITS 56 /* 44-bit PPN */
>
> +#ifdef CONFIG_RISCV_64
> +#define PAGETABLE_ORDER (9)
> +#else /* CONFIG_RISCV_32 */
> +#define PAGETABLE_ORDER (10)
> +#endif
> +
> +#define PAGETABLE_ENTRIES (1 << PAGETABLE_ORDER)
> +
> +#define PTE_PPN_SHIFT 10
> +
> #endif /* __RISCV_PAGE_BITS_H__ */
> diff --git a/xen/arch/riscv/include/asm/page.h
> b/xen/arch/riscv/include/asm/page.h
> new file mode 100644
> index 0000000000..a7e2eee964
> --- /dev/null
> +++ b/xen/arch/riscv/include/asm/page.h
> @@ -0,0 +1,61 @@
> +#ifndef _ASM_RISCV_PAGE_H
> +#define _ASM_RISCV_PAGE_H
> +
> +#include <xen/const.h>
> +#include <xen/types.h>
> +
> +#include <asm/mm.h>
> +#include <asm/page-bits.h>
> +
> +#define VPN_MASK (PAGETABLE_ENTRIES - 1UL)
> +
> +#define XEN_PT_LEVEL_ORDER(lvl) ((lvl) * PAGETABLE_ORDER)
> +#define XEN_PT_LEVEL_SHIFT(lvl) (XEN_PT_LEVEL_ORDER(lvl) + PAGE_SHIFT)
> +#define XEN_PT_LEVEL_SIZE(lvl) (_AT(paddr_t, 1) <<
> XEN_PT_LEVEL_SHIFT(lvl))
> +#define XEN_PT_LEVEL_MAP_MASK(lvl) (~(XEN_PT_LEVEL_SIZE(lvl) - 1))
> +#define XEN_PT_LEVEL_MASK(lvl) (VPN_MASK << XEN_PT_LEVEL_SHIFT(lvl))
> +
> +#define PTE_VALID BIT(0, UL)
> +#define PTE_READABLE BIT(1, UL)
> +#define PTE_WRITABLE BIT(2, UL)
> +#define PTE_EXECUTABLE BIT(3, UL)
> +#define PTE_USER BIT(4, UL)
> +#define PTE_GLOBAL BIT(5, UL)
> +#define PTE_ACCESSED BIT(6, UL)
> +#define PTE_DIRTY BIT(7, UL)
> +#define PTE_RSW (BIT(8, UL) | BIT(9, UL))
> +
> +#define PTE_LEAF_DEFAULT (PTE_VALID | PTE_READABLE | PTE_WRITABLE)
> +#define PTE_TABLE (PTE_VALID)
> +
> +/* Calculate the offsets into the pagetables for a given VA */
> +#define pt_linear_offset(lvl, va) ((va) >> XEN_PT_LEVEL_SHIFT(lvl))
> +
> +#define pt_index(lvl, va) (pt_linear_offset((lvl), (va)) & VPN_MASK)
> +
> +/* Page Table entry */
> +typedef struct {
> +#ifdef CONFIG_RISCV_64
> + uint64_t pte;
> +#else
> + uint32_t pte;
> +#endif
> +} pte_t;
> +
> +static inline pte_t paddr_to_pte(paddr_t paddr,
> + unsigned int permissions)
> +{
> + return (pte_t) { .pte = (paddr_to_pfn(paddr) << PTE_PPN_SHIFT) |
> permissions };
> +}
> +
> +static inline paddr_t pte_to_paddr(pte_t pte)
> +{
> + return pfn_to_paddr(pte.pte >> PTE_PPN_SHIFT);
> +}
> +
> +static inline bool pte_is_valid(pte_t p)
> +{
> + return p.pte & PTE_VALID;
> +}
> +
> +#endif /* _ASM_RISCV_PAGE_H */
> diff --git a/xen/arch/riscv/include/asm/processor.h
> b/xen/arch/riscv/include/asm/processor.h
> index a71448e02e..6db681d805 100644
> --- a/xen/arch/riscv/include/asm/processor.h
> +++ b/xen/arch/riscv/include/asm/processor.h
> @@ -69,6 +69,11 @@ static inline void die(void)
> wfi();
> }
>
> +static inline void sfence_vma(void)
> +{
> + asm volatile ( "sfence.vma" ::: "memory" );
> +}
> +
> #endif /* __ASSEMBLY__ */
>
> #endif /* _ASM_RISCV_PROCESSOR_H */
> diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c
> new file mode 100644
> index 0000000000..692ae9cb5e
> --- /dev/null
> +++ b/xen/arch/riscv/mm.c
> @@ -0,0 +1,276 @@
> +#include <xen/compiler.h>
> +#include <xen/init.h>
> +#include <xen/kernel.h>
> +#include <xen/pfn.h>
> +
> +#include <asm/early_printk.h>
> +#include <asm/csr.h>
> +#include <asm/current.h>
> +#include <asm/mm.h>
> +#include <asm/page.h>
> +#include <asm/processor.h>
> +
> +struct mmu_desc {
> + unsigned int num_levels;
> + unsigned int pgtbl_count;
> + pte_t *next_pgtbl;
> + pte_t *pgtbl_base;
> +};
> +
> +extern unsigned char cpu0_boot_stack[STACK_SIZE];
> +
> +#define PHYS_OFFSET ((unsigned long)_start - XEN_VIRT_START)
> +#define LOAD_TO_LINK(addr) ((addr) - PHYS_OFFSET)
> +#define LINK_TO_LOAD(addr) ((addr) + PHYS_OFFSET)
> +
> +/*
> + * It is expected that Xen won't be more then 2 MB.
> + * The check in xen.lds.S guarantees that.
> + * At least 3 page tables (in case of Sv39 ) are needed to cover 2 MB.
> + * One for each page level table with PAGE_SIZE = 4 Kb.
> + *
> + * One L0 page table can cover 2 MB(512 entries of one page table *
> PAGE_SIZE).
> + *
> + * It might be needed one more page table in case when Xen load address
> + * isn't 2 MB aligned.
> + */
> +#define PGTBL_INITIAL_COUNT ((CONFIG_PAGING_LEVELS - 1) + 1)
> +
> +pte_t __section(".bss.page_aligned") __aligned(PAGE_SIZE)
> +stage1_pgtbl_root[PAGETABLE_ENTRIES];
> +
> +pte_t __section(".bss.page_aligned") __aligned(PAGE_SIZE)
> +stage1_pgtbl_nonroot[PGTBL_INITIAL_COUNT * PAGETABLE_ENTRIES];
> +
> +#define HANDLE_PGTBL(curr_lvl_num) \
> + index = pt_index(curr_lvl_num, page_addr); \
> + if ( pte_is_valid(pgtbl[index]) ) \
> + { \
> + /* Find L{ 0-3 } table */ \
> + pgtbl = (pte_t *)pte_to_paddr(pgtbl[index]); \
> + } \
> + else \
> + { \
> + /* Allocate new L{0-3} page table */ \
> + if ( mmu_desc->pgtbl_count == PGTBL_INITIAL_COUNT ) \
> + { \
> + early_printk("(XEN) No initial table available\n"); \
> + /* panic(), BUG() or ASSERT() aren't ready now. */ \
> + die(); \
> + } \
> + mmu_desc->pgtbl_count++; \
> + pgtbl[index] = paddr_to_pte((unsigned long)mmu_desc->next_pgtbl, \
> + PTE_VALID); \
> + pgtbl = mmu_desc->next_pgtbl; \
> + mmu_desc->next_pgtbl += PAGETABLE_ENTRIES; \
> + }
> +
> +static void __init setup_initial_mapping(struct mmu_desc *mmu_desc,
> + unsigned long map_start,
> + unsigned long map_end,
> + unsigned long pa_start)
> +{
> + unsigned int index;
> + pte_t *pgtbl;
> + unsigned long page_addr;
> +
> + if ( (unsigned long)_start % XEN_PT_LEVEL_SIZE(0) )
> + {
> + early_printk("(XEN) Xen should be loaded at 4k boundary\n");
> + die();
> + }
> +
> + if ( (map_start & ~XEN_PT_LEVEL_MAP_MASK(0)) ||
> + (pa_start & ~XEN_PT_LEVEL_MAP_MASK(0)) )
> + {
> + early_printk("(XEN) map and pa start addresses should be aligned\n");
> + /* panic(), BUG() or ASSERT() aren't ready now. */
> + die();
> + }
> +
> + for ( page_addr = map_start;
> + page_addr < map_end;
> + page_addr += XEN_PT_LEVEL_SIZE(0) )
> + {
> + pgtbl = mmu_desc->pgtbl_base;
> +
> + switch ( mmu_desc->num_levels )
> + {
> + case 4: /* Level 3 */
> + HANDLE_PGTBL(3);
> + case 3: /* Level 2 */
> + HANDLE_PGTBL(2);
> + case 2: /* Level 1 */
> + HANDLE_PGTBL(1);
> + case 1: /* Level 0 */
> + {
> + unsigned long paddr = (page_addr - map_start) + pa_start;
> + unsigned int permissions = PTE_LEAF_DEFAULT;
> + pte_t pte_to_be_written;
> +
> + index = pt_index(0, page_addr);
> +
> + if ( is_kernel_text(LINK_TO_LOAD(page_addr)) ||
> + is_kernel_inittext(LINK_TO_LOAD(page_addr)) )
> + permissions =
> + PTE_EXECUTABLE | PTE_READABLE | PTE_VALID;
> +
> + if ( is_kernel_rodata(LINK_TO_LOAD(page_addr)) )
> + permissions = PTE_READABLE | PTE_VALID;
> +
> + pte_to_be_written = paddr_to_pte(paddr, permissions);
> +
> + if ( !pte_is_valid(pgtbl[index]) )
> + pgtbl[index] = pte_to_be_written;
> + else
> + {
> + if ( (pgtbl[index].pte ^ pte_to_be_written.pte) &
> + ~(PTE_DIRTY | PTE_ACCESSED) )
> + {
> + early_printk("PTE overridden has occurred\n");
> + /* panic(), <asm/bug.h> aren't ready now. */
> + die();
> + }
> + }
> + }
> + }
> + }
> +}
> +#undef HANDLE_PGTBL
> +
> +static bool __init check_pgtbl_mode_support(struct mmu_desc *mmu_desc,
> + unsigned long load_start)
> +{
> + bool is_mode_supported = false;
> + unsigned int index;
> + unsigned int page_table_level = (mmu_desc->num_levels - 1);
> + unsigned level_map_mask = XEN_PT_LEVEL_MAP_MASK(page_table_level);
> +
> + unsigned long aligned_load_start = load_start & level_map_mask;
> + unsigned long aligned_page_size = XEN_PT_LEVEL_SIZE(page_table_level);
> + unsigned long xen_size = (unsigned long)(_end - start);
> +
> + if ( (load_start + xen_size) > (aligned_load_start + aligned_page_size) )
> + {
> + early_printk("please place Xen to be in range of PAGE_SIZE "
> + "where PAGE_SIZE is XEN_PT_LEVEL_SIZE( {L3 | L2 | L1} )
> "
> + "depending on expected SATP_MODE \n"
> + "XEN_PT_LEVEL_SIZE is defined in <asm/page.h>\n");
> + die();
> + }
> +
> + index = pt_index(page_table_level, aligned_load_start);
> + stage1_pgtbl_root[index] = paddr_to_pte(aligned_load_start,
> + PTE_LEAF_DEFAULT |
> PTE_EXECUTABLE);
> +
> + sfence_vma();
> + csr_write(CSR_SATP,
> + PFN_DOWN((unsigned long)stage1_pgtbl_root) |
> + RV_STAGE1_MODE << SATP_MODE_SHIFT);
> +
> + if ( (csr_read(CSR_SATP) >> SATP_MODE_SHIFT) == RV_STAGE1_MODE )
> + is_mode_supported = true;
> +
> + csr_write(CSR_SATP, 0);
> +
> + sfence_vma();
> +
> + /* Clean MMU root page table */
> + stage1_pgtbl_root[index] = paddr_to_pte(0x0, 0x0);
> +
> + return is_mode_supported;
> +}
> +
> +/*
> + * setup_initial_pagetables:
> + *
> + * Build the page tables for Xen that map the following:
> + * 1. Calculate page table's level numbers.
> + * 2. Init mmu description structure.
> + * 3. Check that linker addresses range doesn't overlap
> + * with load addresses range
> + * 4. Map all linker addresses and load addresses ( it shouldn't
> + * be 1:1 mapped and will be 1:1 mapped only in case if
> + * linker address is equal to load address ) with
> + * RW permissions by default.
> + * 5. Setup proper PTE permissions for each section.
> + */
> +void __init setup_initial_pagetables(void)
> +{
> + struct mmu_desc mmu_desc = { CONFIG_PAGING_LEVELS, 0, NULL, NULL };
> +
> + /*
> + * Access to _start, _end is always PC-relative thereby when access
> + * them we will get load adresses of start and end of Xen.
> + * To get linker addresses LOAD_TO_LINK() is required to use.
> + */
> + unsigned long load_start = (unsigned long)_start;
> + unsigned long load_end = (unsigned long)_end;
> + unsigned long linker_start = LOAD_TO_LINK(load_start);
> + unsigned long linker_end = LOAD_TO_LINK(load_end);
> +
> + if ( (linker_start != load_start) &&
> + (linker_start <= load_end) && (load_start <= linker_end) )
> + {
> + early_printk("(XEN) linker and load address ranges overlap\n");
> + die();
> + }
> +
> + if ( !check_pgtbl_mode_support(&mmu_desc, load_start) )
> + {
> + early_printk("requested MMU mode isn't supported by CPU\n"
> + "Please choose different in <asm/config.h>\n");
> + die();
> + }
> +
> + mmu_desc.pgtbl_base = stage1_pgtbl_root;
> + mmu_desc.next_pgtbl = stage1_pgtbl_nonroot;
> +
> + setup_initial_mapping(&mmu_desc,
> + linker_start,
> + linker_end,
> + load_start);
> +}
> +
> +void __init noreturn noinline enable_mmu()
> +{
> + /*
> + * Calculate a linker time address of the mmu_is_enabled
> + * label and update CSR_STVEC with it.
> + * MMU is configured in a way where linker addresses are mapped
> + * on load addresses so in a case when linker addresses are not equal
> + * to load addresses, after MMU is enabled, it will cause
> + * an exception and jump to linker time addresses.
> + * Otherwise if load addresses are equal to linker addresses the code
> + * after mmu_is_enabled label will be executed without exception.
> + */
> + csr_write(CSR_STVEC, LOAD_TO_LINK((unsigned long)&&mmu_is_enabled));
> +
> + /* Ensure page table writes precede loading the SATP */
> + sfence_vma();
> +
> + /* Enable the MMU and load the new pagetable for Xen */
> + csr_write(CSR_SATP,
> + PFN_DOWN((unsigned long)stage1_pgtbl_root) |
> + RV_STAGE1_MODE << SATP_MODE_SHIFT);
> +
> + asm volatile ( ".p2align 2" );
> + mmu_is_enabled:
> + /*
> + * Stack should be re-inited as:
> + * 1. Right now an address of the stack is relative to load time
> + * addresses what will cause an issue in case of load start address
> + * isn't equal to linker start address.
> + * 2. Addresses in stack are all load time relative which can be an
> + * issue in case when load start address isn't equal to linker
> + * start address.
> + *
> + * We can't return to the caller because the stack was reseted
> + * and it may have stash some variable on the stack.
> + * Jump to a brand new function as the stack was reseted
> + */
> +
> + switch_stack_and_jump((unsigned long)cpu0_boot_stack + STACK_SIZE,
> + cont_after_mmu_is_enabled);
> +}
> +
> diff --git a/xen/arch/riscv/setup.c b/xen/arch/riscv/setup.c
> index 3786f337e0..315804aa87 100644
> --- a/xen/arch/riscv/setup.c
> +++ b/xen/arch/riscv/setup.c
> @@ -2,6 +2,7 @@
> #include <xen/init.h>
>
> #include <asm/early_printk.h>
> +#include <asm/mm.h>
>
> /* Xen stack for bringing up the first CPU. */
> unsigned char __initdata cpu0_boot_stack[STACK_SIZE]
> @@ -26,3 +27,13 @@ void __init noreturn start_xen(unsigned long bootcpu_id,
>
> unreachable();
> }
> +
> +void __init noreturn cont_after_mmu_is_enabled(void)
> +{
> + early_printk("All set up\n");
> +
> + for ( ;; )
> + asm volatile ("wfi");
> +
> + unreachable();
> +}
> diff --git a/xen/arch/riscv/xen.lds.S b/xen/arch/riscv/xen.lds.S
> index 31e0d3576c..fe475d096d 100644
> --- a/xen/arch/riscv/xen.lds.S
> +++ b/xen/arch/riscv/xen.lds.S
> @@ -172,3 +172,6 @@ ASSERT(IS_ALIGNED(__bss_end, POINTER_ALIGN),
> "__bss_end is misaligned")
>
> ASSERT(!SIZEOF(.got), ".got non-empty")
> ASSERT(!SIZEOF(.got.plt), ".got.plt non-empty")
> +
> +ASSERT(_end - _start <= MB(2), "Xen too large for early-boot assumptions")
> +
> --
> 2.40.1
>
>
LGTM. Nice code to boot!
Acked-by: Bobby Eshleman <bobbyeshleman@xxxxxxxxx>
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