From: Andrew Jones <andrew.jones@linux.dev>
To: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: pbonzini@redhat.com, thuth@redhat.com, kvm@vger.kernel.org,
kvmarm@lists.cs.columbia.edu, nikos.nikoleris@arm.com
Subject: Re: [kvm-unit-tests RFC PATCH 16/19] arm/arm64: Allocate secondaries' stack using the page allocator
Date: Tue, 20 Sep 2022 11:58:02 +0200 [thread overview]
Message-ID: <20220920095802.bukms5w2phaxyaao@kamzik> (raw)
In-Reply-To: <20220809091558.14379-17-alexandru.elisei@arm.com>
On Tue, Aug 09, 2022 at 10:15:55AM +0100, Alexandru Elisei wrote:
> The vmalloc allocator returns non-id mapped addresses, where the virtual
> address is different than the physical address. This makes it impossible
> to access the stack of the secondary CPUs while the MMU is disabled.
>
> On arm, THREAD_SIZE is 16K and PAGE_SIZE is 4K, which makes THREAD_SIZE
> a power of two multiple of PAGE_SIZE. On arm64, THREAD_SIZE is 16 when
> PAGE_SIZE is 4K or 16K, and 64K when PAGE_SIZE is 64K. In all cases,
> THREAD_SIZE is a power of two multiple of PAGE_SIZE. As a result, using
> memalign_pages() for the stack won't lead to wasted memory.
>
> memalign_pages() allocates memory in chunks of power of two number of
> pages, aligned to the allocation size, which makes it a drop-in
> replacement for vm_memalign (which is the value for alloc_ops->memalign
> when the stack is allocated).
>
> Using memalign_pages() has two distinct benefits:
>
> 1. The secondary CPUs' stack can be used with the MMU off.
>
> 2. The secondary CPUs' stack is identify mapped similar to the stack for
> the primary CPU, which makes the configuration of the CPUs consistent.
>
> memalign_pages_flags() has been used instead of memalign_pages() to
> instruct the allocator not to zero the stack, as it's already zeroed in the
> entry code.
>
> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> ---
> lib/arm/asm/thread_info.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lib/arm/asm/thread_info.h b/lib/arm/asm/thread_info.h
> index eaa72582af86..190e082cbba0 100644
> --- a/lib/arm/asm/thread_info.h
> +++ b/lib/arm/asm/thread_info.h
> @@ -25,6 +25,7 @@
> #ifndef __ASSEMBLY__
> #include <asm/processor.h>
> #include <alloc.h>
> +#include <alloc_page.h>
>
> #ifdef __arm__
> #include <asm/ptrace.h>
> @@ -40,7 +41,7 @@
>
> static inline void *thread_stack_alloc(void)
> {
> - void *sp = memalign(THREAD_ALIGNMENT, THREAD_SIZE);
> + void *sp = memalign_pages_flags(THREAD_ALIGNMENT, THREAD_SIZE, FLAG_DONTZERO);
> return sp + THREAD_START_SP;
> }
>
> --
> 2.37.1
>
Reviewed-by: Andrew Jones <andrew.jones@linux.dev>
next prev parent reply other threads:[~2022-09-20 9:58 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-09 9:15 [kvm-unit-tests RFC PATCH 00/19] arm/arm64: Rework cache maintenance at boot Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 01/19] Makefile: Define __ASSEMBLY__ for assembly files Alexandru Elisei
2022-08-09 12:36 ` Nikos Nikoleris
2022-09-20 8:11 ` Andrew Jones
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 02/19] lib/alloc_phys: Initialize align_min Alexandru Elisei
2022-09-20 8:20 ` Andrew Jones
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 03/19] lib/alloc_phys: Use phys_alloc_aligned_safe and rename it to memalign_early Alexandru Elisei
2022-09-20 8:27 ` Andrew Jones
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 04/19] powerpc: Use the page allocator Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 05/19] lib/alloc_phys: Remove locking Alexandru Elisei
2022-09-20 8:45 ` Andrew Jones
2022-09-20 13:20 ` Alexandru Elisei
2022-09-20 14:59 ` Andrew Jones
2022-09-26 15:04 ` Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 06/19] lib/alloc_phys: Remove allocation accounting Alexandru Elisei
2022-09-20 8:40 ` Andrew Jones
2022-09-20 13:19 ` Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 07/19] arm/arm64: Mark the phys_end parameter as unused in setup_mmu() Alexandru Elisei
2022-09-20 8:58 ` Andrew Jones
2022-09-26 11:01 ` Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 08/19] arm/arm64: Use pgd_alloc() to allocate mmu_idmap Alexandru Elisei
2022-09-20 9:05 ` Andrew Jones
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 09/19] arm/arm64: Zero secondary CPUs' stack Alexandru Elisei
2022-08-09 12:56 ` Nikos Nikoleris
2022-08-10 9:42 ` Alexandru Elisei
2022-08-10 10:00 ` Nikos Nikoleris
2022-09-20 9:24 ` Andrew Jones
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 10/19] arm/arm64: Enable the MMU early Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 11/19] arm/arm64: Map the UART when creating the translation tables Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 12/19] arm/arm64: assembler.h: Replace size with end address for dcache_by_line_op Alexandru Elisei
2022-08-09 13:01 ` Nikos Nikoleris
2022-09-20 9:37 ` Andrew Jones
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 13/19] arm: page.h: Add missing libcflat.h include Alexandru Elisei
2022-09-20 9:39 ` Andrew Jones
2022-09-26 11:02 ` Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 14/19] arm/arm64: Add C functions for doing cache maintenance Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 15/19] lib/alloc_phys: Add callback to perform " Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 16/19] arm/arm64: Allocate secondaries' stack using the page allocator Alexandru Elisei
2022-09-20 9:58 ` Andrew Jones [this message]
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 17/19] arm/arm64: Configure secondaries' stack before enabling the MMU Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 18/19] arm/arm64: Perform dcache maintenance at boot Alexandru Elisei
2022-08-09 9:15 ` [kvm-unit-tests RFC PATCH 19/19] arm/arm64: Rework the cache maintenance in asm_mmu_disable Alexandru Elisei
2022-08-09 13:53 ` Nikos Nikoleris
2022-08-09 14:22 ` Alexandru Elisei
2022-08-09 15:53 ` Nikos Nikoleris
2022-08-09 16:53 ` Alexandru Elisei
2022-08-09 19:48 ` Nikos Nikoleris
2022-08-10 8:52 ` Alexandru Elisei
2022-08-09 9:49 ` [kvm-unit-tests RFC PATCH 00/19] arm/arm64: Rework cache maintenance at boot Alexandru Elisei
2023-11-05 10:16 ` Alexandru Elisei
2023-11-06 9:37 ` Shaoqin Huang
2023-11-07 9:01 ` Alexandru Elisei
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