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Re: [patch v3 33/36] x86/apic: Save the APIC virtual base address
- To: Thomas Gleixner <tglx@xxxxxxxxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>
- From: Sergey Shtylyov <s.shtylyov@xxxxxx>
- Date: Tue, 9 May 2023 12:20:06 +0300
- Cc: <x86@xxxxxxxxxx>, David Woodhouse <dwmw2@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Brian Gerst <brgerst@xxxxxxxxx>, Arjan van de Veen <arjan@xxxxxxxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Paul McKenney <paulmck@xxxxxxxxxx>, Tom Lendacky <thomas.lendacky@xxxxxxx>, Sean Christopherson <seanjc@xxxxxxxxxx>, Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>, Paul Menzel <pmenzel@xxxxxxxxxxxxx>, "Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxx>, Piotr Gorski <lucjan.lucjanov@xxxxxxxxx>, Usama Arif <usama.arif@xxxxxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Russell King <linux@xxxxxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>, Catalin Marinas <catalin.marinas@xxxxxxx>, Will Deacon <will@xxxxxxxxxx>, Guo Ren <guoren@xxxxxxxxxx>, <linux-csky@xxxxxxxxxxxxxxx>, Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>, <linux-mips@xxxxxxxxxxxxxxx>, "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>, Helge Deller <deller@xxxxxx>, <linux-parisc@xxxxxxxxxxxxxxx>, Paul Walmsley <paul.walmsley@xxxxxxxxxx>, Palmer Dabbelt <palmer@xxxxxxxxxxx>, <linux-riscv@xxxxxxxxxxxxxxxxxxx>, Mark Rutland <mark.rutland@xxxxxxx>, Sabin Rapan <sabrapan@xxxxxxxxxx>, "Michael Kelley (LINUX)" <mikelley@xxxxxxxxxxxxx>
- Delivery-date: Tue, 09 May 2023 09:20:37 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hello!
On 5/8/23 10:44 PM, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>
> For parallel CPU brinugp it's required to read the APIC ID in the low level
> startup code. The virtual APIC base address is a constant because its a
> fix-mapped address. Exposing that constant which is composed via macros to
> assembly code is non-trivial dues to header inclusion hell.
s/dues/due/?
> Aside of that it's constant only because of the vsyscall ABI
> requirement. Once vsyscall is out of the picture the fixmap can be placed
> at runtime.
>
> Avoid header hell, stay flexible and store the address in a variable which
> can be exposed to the low level startup code.
>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Tested-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
[...]
MBR, Sergey
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