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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v5 2/5] xen/arm64: Rework the memory layout
> On 23 Feb 2023, at 15:09, Bertrand Marquis <Bertrand.Marquis@xxxxxxx> wrote: > > Hi Julien, > >> On 27 Jan 2023, at 20:55, Julien Grall <julien@xxxxxxx> wrote: >> >> From: Julien Grall <jgrall@xxxxxxxxxx> >> >> Xen is currently not fully compliant with the Arm Arm because it will >> switch the TTBR with the MMU on. >> >> In order to be compliant, we need to disable the MMU before >> switching the TTBR. The implication is the page-tables should >> contain an identity mapping of the code switching the TTBR. >> >> In most of the case we expect Xen to be loaded in low memory. I am aware >> of one platform (i.e AMD Seattle) where the memory start above 512GB. >> To give us some slack, consider that Xen may be loaded in the first 2TB >> of the physical address space. >> >> The memory layout is reshuffled to keep the first four slots of the zeroeth >> level free. Xen will now be loaded at (2TB + 2MB). This requires a slight >> tweak of the boot code because XEN_VIRT_START cannot be used as an >> immediate. >> >> This reshuffle will make trivial to create a 1:1 mapping when Xen is >> loaded below 2TB. >> >> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx> >> Tested-by: Luca Fancellu <luca.fancellu@xxxxxxx> >> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx> > > With the finding for the comparison to 4 and not 2 found by Michal fixed: > Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx > <mailto:bertrand.marquis@xxxxxxx>> Sorry for that: Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx> Cheers Bertrand > > Cheers > Bertrand > >> >> --- >> Changes in v5: >> - We are reserving 4 slots rather than 2. >> - Fix the addresses in the layout comment. >> - Fix the size of the region in the layout comment >> - Add Luca's tested-by (the reviewed-by was not added >> because of the changes requested by Michal >> - Add Michal's reviewed-by >> >> Changes in v4: >> - Correct the documentation >> - The start address is 2TB, so slot0 is 4 not 2. >> >> Changes in v2: >> - Reword the commit message >> - Load Xen at 2TB + 2MB >> - Update the documentation to reflect the new layout >> --- >> xen/arch/arm/arm64/head.S | 3 ++- >> xen/arch/arm/include/asm/config.h | 34 +++++++++++++++++++++---------- >> xen/arch/arm/mm.c | 11 +++++----- >> 3 files changed, 31 insertions(+), 17 deletions(-) >> >> diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S >> index 4a3f87117c83..663f5813b12e 100644 >> --- a/xen/arch/arm/arm64/head.S >> +++ b/xen/arch/arm/arm64/head.S >> @@ -607,7 +607,8 @@ create_page_tables: >> * need an additional 1:1 mapping, the virtual mapping will >> * suffice. >> */ >> - cmp x19, #XEN_VIRT_START >> + ldr x0, =XEN_VIRT_START >> + cmp x19, x0 >> bne 1f >> ret >> 1: >> diff --git a/xen/arch/arm/include/asm/config.h >> b/xen/arch/arm/include/asm/config.h >> index 5df0e4c4959b..e388462c23d1 100644 >> --- a/xen/arch/arm/include/asm/config.h >> +++ b/xen/arch/arm/include/asm/config.h >> @@ -72,16 +72,13 @@ >> #include <xen/page-size.h> >> >> /* >> - * Common ARM32 and ARM64 layout: >> + * ARM32 layout: >> * 0 - 2M Unmapped >> * 2M - 4M Xen text, data, bss >> * 4M - 6M Fixmap: special-purpose 4K mapping slots >> * 6M - 10M Early boot mapping of FDT >> * 10M - 12M Livepatch vmap (if compiled in) >> * >> - * ARM32 layout: >> - * 0 - 12M <COMMON> >> - * >> * 32M - 128M Frametable: 32 bytes per page for 12GB of RAM >> * 256M - 1G VMAP: ioremap and early_ioremap use this virtual address >> * space >> @@ -90,14 +87,23 @@ >> * 2G - 4G Domheap: on-demand-mapped >> * >> * ARM64 layout: >> - * 0x0000000000000000 - 0x0000007fffffffff (512GB, L0 slot [0]) >> - * 0 - 12M <COMMON> >> + * 0x0000000000000000 - 0x000001ffffffffff (2TB, L0 slots [0..3]) >> + * >> + * Reserved to identity map Xen >> + * >> + * 0x0000020000000000 - 0x0000027fffffffff (512GB, L0 slot [4] >> + * (Relative offsets) >> + * 0 - 2M Unmapped >> + * 2M - 4M Xen text, data, bss >> + * 4M - 6M Fixmap: special-purpose 4K mapping slots >> + * 6M - 10M Early boot mapping of FDT >> + * 10M - 12M Livepatch vmap (if compiled in) >> * >> * 1G - 2G VMAP: ioremap and early_ioremap >> * >> * 32G - 64G Frametable: 56 bytes per page for 2TB of RAM >> * >> - * 0x0000008000000000 - 0x00007fffffffffff (127.5TB, L0 slots [1..255]) >> + * 0x0000028000000000 - 0x00007fffffffffff (125TB, L0 slots [5..255]) >> * Unused >> * >> * 0x0000800000000000 - 0x000084ffffffffff (5TB, L0 slots [256..265]) >> @@ -107,7 +113,17 @@ >> * Unused >> */ >> >> +#ifdef CONFIG_ARM_32 >> #define XEN_VIRT_START _AT(vaddr_t, MB(2)) >> +#else >> + >> +#define SLOT0_ENTRY_BITS 39 >> +#define SLOT0(slot) (_AT(vaddr_t,slot) << SLOT0_ENTRY_BITS) >> +#define SLOT0_ENTRY_SIZE SLOT0(1) >> + >> +#define XEN_VIRT_START (SLOT0(4) + _AT(vaddr_t, MB(2))) >> +#endif >> + >> #define XEN_VIRT_SIZE _AT(vaddr_t, MB(2)) >> >> #define FIXMAP_VIRT_START (XEN_VIRT_START + XEN_VIRT_SIZE) >> @@ -163,10 +179,6 @@ >> >> #else /* ARM_64 */ >> >> -#define SLOT0_ENTRY_BITS 39 >> -#define SLOT0(slot) (_AT(vaddr_t,slot) << SLOT0_ENTRY_BITS) >> -#define SLOT0_ENTRY_SIZE SLOT0(1) >> - >> #define VMAP_VIRT_START GB(1) >> #define VMAP_VIRT_SIZE GB(1) >> >> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c >> index f758cad545fa..0b0edf28d57a 100644 >> --- a/xen/arch/arm/mm.c >> +++ b/xen/arch/arm/mm.c >> @@ -153,7 +153,7 @@ static void __init __maybe_unused build_assertions(void) >> #endif >> /* Page table structure constraints */ >> #ifdef CONFIG_ARM_64 >> - BUILD_BUG_ON(zeroeth_table_offset(XEN_VIRT_START)); >> + BUILD_BUG_ON(zeroeth_table_offset(XEN_VIRT_START) < 2); >> #endif >> BUILD_BUG_ON(first_table_offset(XEN_VIRT_START)); >> #ifdef CONFIG_ARCH_MAP_DOMAIN_PAGE >> @@ -496,10 +496,11 @@ void __init setup_pagetables(unsigned long >> boot_phys_offset) >> phys_offset = boot_phys_offset; >> >> #ifdef CONFIG_ARM_64 >> - p = (void *) xen_pgtable; >> - p[0] = pte_of_xenaddr((uintptr_t)xen_first); >> - p[0].pt.table = 1; >> - p[0].pt.xn = 0; >> + pte = pte_of_xenaddr((uintptr_t)xen_first); >> + pte.pt.table = 1; >> + pte.pt.xn = 0; >> + xen_pgtable[zeroeth_table_offset(XEN_VIRT_START)] = pte; >> + >> p = (void *) xen_first; >> #else >> p = (void *) cpu0_pgtable; >> -- >> 2.38.1
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