From: Alexandru Elisei <alexandru.elisei@arm.com>
To: Andrew Jones <drjones@redhat.com>, kvm@vger.kernel.org
Cc: nikos.nikoleris@arm.com, andre.przywara@arm.com, eric.auger@redhat.com
Subject: Re: [PATCH kvm-unit-tests 5/8] arm/arm64: mmu: Remove memory layout assumptions
Date: Thu, 15 Apr 2021 16:48:41 +0100 [thread overview]
Message-ID: <b1e637b2-b926-18f3-16d3-e112d51acb8f@arm.com> (raw)
In-Reply-To: <20210407185918.371983-6-drjones@redhat.com>
Hi Drew,
On 4/7/21 7:59 PM, Andrew Jones wrote:
> Rather than making too many assumptions about the memory layout
> in mmu code, just set up the page tables per the memory regions
> (which means putting all the memory layout assumptions in setup).
> To ensure we get the right default flags set we need to split the
> primary region into two regions for code and data.
>
> We still only expect the primary regions to be present, but the
> next patch will remove that assumption too.
Nitpick, but we still make assumptions about the memory layout:
- In setup_mmu(), we limit the maximum linear address to 3GiB, but on arm64 we can
have memory starting well above that.
- In mem_init(), we still have the predefined I/O regions.
I don't know if this is a rebasing error or intentional. If it's intentional, I
think it should be mentioned in the commit message, if only to say they will be
removed in a later patch (like you do with the primary region).
>
> Signed-off-by: Andrew Jones <drjones@redhat.com>
> ---
> lib/arm/asm/setup.h | 1 +
> lib/arm/mmu.c | 26 +++++++++++++++-----------
> lib/arm/setup.c | 22 ++++++++++++++--------
> 3 files changed, 30 insertions(+), 19 deletions(-)
>
> diff --git a/lib/arm/asm/setup.h b/lib/arm/asm/setup.h
> index c8afb2493f8d..210c14f818fb 100644
> --- a/lib/arm/asm/setup.h
> +++ b/lib/arm/asm/setup.h
> @@ -15,6 +15,7 @@ extern int nr_cpus;
>
> #define MR_F_PRIMARY (1U << 0)
> #define MR_F_IO (1U << 1)
> +#define MR_F_CODE (1U << 2)
> #define MR_F_UNKNOWN (1U << 31)
>
> struct mem_region {
> diff --git a/lib/arm/mmu.c b/lib/arm/mmu.c
> index a7b7ae51afe3..edd2b9da809b 100644
> --- a/lib/arm/mmu.c
> +++ b/lib/arm/mmu.c
> @@ -20,8 +20,6 @@
>
> #include <linux/compiler.h>
>
> -extern unsigned long etext;
> -
> #define MMU_MAX_PERSISTENT_MAPS 64
>
> struct mmu_persistent_map {
> @@ -208,7 +206,7 @@ void mmu_set_range_sect(pgd_t *pgtable, uintptr_t virt_offset,
>
> void *setup_mmu(phys_addr_t phys_end)
> {
> - uintptr_t code_end = (uintptr_t)&etext;
> + struct mem_region *r;
>
> /* 0G-1G = I/O, 1G-3G = identity, 3G-4G = vmalloc */
> if (phys_end > (3ul << 30))
> @@ -223,14 +221,20 @@ void *setup_mmu(phys_addr_t phys_end)
>
> mmu_idmap = alloc_page();
>
> - /* armv8 requires code shared between EL1 and EL0 to be read-only */
> - mmu_set_range_ptes(mmu_idmap, PHYS_OFFSET,
> - PHYS_OFFSET, code_end,
> - __pgprot(PTE_WBWA | PTE_RDONLY | PTE_USER));
> -
> - mmu_set_range_ptes(mmu_idmap, code_end,
> - code_end, phys_end,
> - __pgprot(PTE_WBWA | PTE_USER));
> + for (r = mem_regions; r->end; ++r) {
> + if (r->flags & MR_F_IO) {
> + continue;
> + } else if (r->flags & MR_F_CODE) {
> + assert_msg(r->flags & MR_F_PRIMARY, "Unexpected code region");
> + /* armv8 requires code shared between EL1 and EL0 to be read-only */
> + mmu_set_range_ptes(mmu_idmap, r->start, r->start, r->end,
> + __pgprot(PTE_WBWA | PTE_USER | PTE_RDONLY));
> + } else {
> + assert_msg(r->flags & MR_F_PRIMARY, "Unexpected data region");
> + mmu_set_range_ptes(mmu_idmap, r->start, r->start, r->end,
> + __pgprot(PTE_WBWA | PTE_USER));
> + }
> + }
This looks good.
>
> mmu_set_persistent_maps(mmu_idmap);
>
> diff --git a/lib/arm/setup.c b/lib/arm/setup.c
> index 9c16f6004e9f..9da5d24b0be9 100644
> --- a/lib/arm/setup.c
> +++ b/lib/arm/setup.c
> @@ -31,6 +31,7 @@
> #define NR_INITIAL_MEM_REGIONS 16
>
> extern unsigned long stacktop;
> +extern unsigned long etext;
>
> struct timer_state __timer_state;
>
> @@ -88,10 +89,12 @@ unsigned int mem_region_get_flags(phys_addr_t paddr)
>
> static void mem_init(phys_addr_t freemem_start)
> {
> + phys_addr_t code_end = (phys_addr_t)(unsigned long)&etext;
> struct dt_pbus_reg regs[NR_INITIAL_MEM_REGIONS];
> - struct mem_region primary, mem = {
> + struct mem_region mem = {
> .start = (phys_addr_t)-1,
> };
> + struct mem_region *primary = NULL;
> phys_addr_t base, top;
> int nr_regs, nr_io = 0, i;
>
> @@ -110,8 +113,6 @@ static void mem_init(phys_addr_t freemem_start)
> nr_regs = dt_get_memory_params(regs, NR_INITIAL_MEM_REGIONS - nr_io);
> assert(nr_regs > 0);
>
> - primary = (struct mem_region){ 0 };
> -
> for (i = 0; i < nr_regs; ++i) {
> struct mem_region *r = &mem_regions[nr_io + i];
>
> @@ -123,7 +124,7 @@ static void mem_init(phys_addr_t freemem_start)
> */
> if (freemem_start >= r->start && freemem_start < r->end) {
> r->flags |= MR_F_PRIMARY;
Here we mark mem_regions[nr_io + i] as primary...
> - primary = *r;
> + primary = r;
> }
>
> /*
> @@ -135,13 +136,18 @@ static void mem_init(phys_addr_t freemem_start)
> if (r->end > mem.end)
> mem.end = r->end;
> }
> - assert(primary.end != 0);
> + assert(primary);
> assert(!(mem.start & ~PHYS_MASK) && !((mem.end - 1) & ~PHYS_MASK));
>
> - __phys_offset = primary.start; /* PHYS_OFFSET */
> - __phys_end = primary.end; /* PHYS_END */
> + __phys_offset = primary->start; /* PHYS_OFFSET */
> + __phys_end = primary->end; /* PHYS_END */
> +
> + /* Split the primary region into two regions; code and data */
> + mem.start = code_end, mem.end = primary->end, mem.flags = MR_F_PRIMARY;
Here we mark mem as primary...
> + mem_regions[nr_io + i] = mem;
And then we set mem_regions[nr_io + nr_regs] to mem, which I think means we can
end up with two primary memory regions. Am I missing something?
> + primary->end = code_end, primary->flags |= MR_F_CODE;
Please consider splitting the assignments each on its own line, because it makes
the code so hard to read (and I assume really easy to miss if we ever change
something).
Thanks,
Alex
>
> - phys_alloc_init(freemem_start, primary.end - freemem_start);
> + phys_alloc_init(freemem_start, __phys_end - freemem_start);
> phys_alloc_set_minimum_alignment(SMP_CACHE_BYTES);
>
> phys_alloc_get_unused(&base, &top);
next prev parent reply other threads:[~2021-04-15 15:48 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-07 18:59 [PATCH kvm-unit-tests 0/8] arm/arm64: Prepare for target-efi Andrew Jones
2021-04-07 18:59 ` [PATCH kvm-unit-tests 1/8] arm/arm64: Reorganize cstart assembler Andrew Jones
2021-04-09 17:18 ` Nikos Nikoleris
2021-04-09 17:28 ` Andrew Jones
2021-04-13 16:34 ` Alexandru Elisei
2021-04-14 8:59 ` Andrew Jones
2021-04-14 15:15 ` Alexandru Elisei
2021-04-15 13:03 ` Andrew Jones
2021-04-07 18:59 ` [PATCH kvm-unit-tests 2/8] arm/arm64: Move setup_vm into setup Andrew Jones
2021-04-09 17:24 ` Nikos Nikoleris
2021-04-14 15:19 ` Alexandru Elisei
2021-04-07 18:59 ` [PATCH kvm-unit-tests 3/8] pci-testdev: ioremap regions Andrew Jones
2021-04-13 14:12 ` Nikos Nikoleris
2021-04-07 18:59 ` [PATCH kvm-unit-tests 4/8] arm/arm64: mmu: Stop mapping an assumed IO region Andrew Jones
2021-04-13 14:06 ` Nikos Nikoleris
2021-04-14 15:42 ` Alexandru Elisei
2021-04-15 13:09 ` Andrew Jones
2021-04-07 18:59 ` [PATCH kvm-unit-tests 5/8] arm/arm64: mmu: Remove memory layout assumptions Andrew Jones
2021-04-13 14:27 ` Nikos Nikoleris
2021-04-15 15:48 ` Alexandru Elisei [this message]
2021-04-15 17:11 ` Andrew Jones
2021-04-19 15:09 ` Alexandru Elisei
2021-04-07 18:59 ` [PATCH kvm-unit-tests 6/8] arm/arm64: setup: Consolidate " Andrew Jones
2021-04-13 16:41 ` Nikos Nikoleris
2021-04-14 9:03 ` Andrew Jones
2021-04-15 16:59 ` Alexandru Elisei
2021-04-15 17:25 ` Andrew Jones
2021-04-19 15:56 ` Alexandru Elisei
2021-04-19 15:59 ` Alexandru Elisei
2021-04-19 17:53 ` Andrew Jones
2021-04-07 18:59 ` [PATCH kvm-unit-tests 7/8] chr-testdev: Silently fail init Andrew Jones
2021-04-13 16:42 ` Nikos Nikoleris
2021-04-15 17:03 ` Alexandru Elisei
2021-04-07 18:59 ` [PATCH kvm-unit-tests 8/8] arm/arm64: psci: don't assume method is hvc Andrew Jones
2021-04-09 17:46 ` Nikos Nikoleris
2021-04-14 9:06 ` Andrew Jones
2021-04-19 16:33 ` Alexandru Elisei
2021-04-19 18:13 ` Andrew Jones
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