From: james.morse@arm•com (James Morse)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v3 04/13] arm64: alternatives: use tpidr_el2 on VHE hosts
Date: Fri, 13 Oct 2017 17:50:45 +0100 [thread overview]
Message-ID: <59E0EEE5.2020208@arm.com> (raw)
In-Reply-To: <20171013153148.dnejsvhxeui6opfw@armageddon.cambridge.arm.com>
Hi Catalin,
On 13/10/17 16:31, Catalin Marinas wrote:
> On Fri, Sep 22, 2017 at 07:26:05PM +0100, James Morse wrote:
>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>> index cd52d365d1f0..8e4c7da2b126 100644
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -1308,3 +1309,25 @@ static int __init enable_mrs_emulation(void)
>> }
>>
>> late_initcall(enable_mrs_emulation);
>> +
>> +int cpu_copy_el2regs(void *__unused)
>> +{
>> + int do_copyregs = 0;
>> +
>> + /*
>> + * Copy register values that aren't redirected by hardware.
>> + *
>> + * Before code patching, we only set tpidr_el1, all CPUs need to copy
>> + * this value to tpidr_el2 before we patch the code. Once we've done
>> + * that, freshly-onlined CPUs will set tpidr_el2, so we don't need to
>> + * do anything here.
>> + */
>> + asm volatile(ALTERNATIVE("mov %0, #1", "mov %0, #0",
>> + ARM64_HAS_VIRT_HOST_EXTN)
>> + : "=r" (do_copyregs) : : );
>
> Can you just do:
>
> if (cpu_have_const_cap(ARM64_HAS_VIRT_HOST_EXTN))
> write_sysreg(read_sysreg(tpidr_el1), tpidr_el2);
>
> At this point the capability bits should be set and the jump labels
> enabled.
These are enabled too early, we haven't done patching yet.
We need to copy tpidr_el1 -> tpidr_el2 on all CPUs that are online before code
patching.
After code patching new CPUs set tpidr_el2 when they come online, so we don't
need to do the copy... but this enable method is still called. There is nothing
for us to do, and tpidr_el1 now contains junk, so the copy
cpu_have_const_cap() is great for knowing if we have a feature, here we want to
know if we've done the patching for this feature.
I can wrap the ALTERNATIVE() into a helper, something like:
> arm64_alternatives_applied(ARM64_HAS_VIRT_HOST_EXTN)
which should make it clearer.
Christoffer had the same question at connect, so I evidently haven't found the
right way of describing this yet.
> Otherwise:
>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm•com>
Thanks for taking a look, I'll leave this RB until your happy with the
ALTERNATIVE() hackery above.
James
next prev parent reply other threads:[~2017-10-13 16:50 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-22 18:26 [PATCH v3 00/13] arm64/firmware: Software Delegated Exception Interface James Morse
2017-09-22 18:26 ` [PATCH v3 01/13] KVM: arm64: Store vcpu on the stack during __guest_enter() James Morse
2017-09-22 18:26 ` [PATCH v3 02/13] KVM: arm/arm64: Convert kvm_host_cpu_state to a static per-cpu allocation James Morse
2017-09-22 18:26 ` [PATCH v3 03/13] KVM: arm64: Change hyp_panic()s dependency on tpidr_el2 James Morse
2017-09-22 18:26 ` [PATCH v3 04/13] arm64: alternatives: use tpidr_el2 on VHE hosts James Morse
2017-10-13 15:31 ` Catalin Marinas
2017-10-13 16:50 ` James Morse [this message]
2017-10-16 9:58 ` Catalin Marinas
2017-10-17 16:36 ` James Morse
2017-10-16 10:17 ` Catalin Marinas
2017-09-22 18:26 ` [PATCH v3 05/13] KVM: arm64: Stop save/restoring host tpidr_el1 on VHE James Morse
2017-09-22 18:26 ` [PATCH v3 06/13] Docs: dt: add devicetree binding for describing arm64 SDEI firmware James Morse
2017-09-22 18:26 ` [PATCH v3 07/13] firmware: arm_sdei: Add driver for Software Delegated Exceptions James Morse
2017-10-13 15:49 ` Catalin Marinas
2017-09-22 18:26 ` [PATCH v3 08/13] arm64: Add vmap_stack header file James Morse
2017-10-13 15:42 ` Catalin Marinas
2017-10-17 16:34 ` James Morse
2017-09-22 18:26 ` [PATCH v3 09/13] arm64: kernel: Add arch-specific SDEI entry code and CPU masking James Morse
2017-10-16 13:41 ` Catalin Marinas
2017-10-17 16:34 ` James Morse
2017-10-18 10:54 ` Catalin Marinas
2017-09-22 18:26 ` [PATCH v3 10/13] firmware: arm_sdei: Add support for CPU and system power states James Morse
2017-10-16 13:52 ` Catalin Marinas
2017-10-17 16:34 ` James Morse
2017-09-22 18:26 ` [PATCH v3 11/13] firmware: arm_sdei: add support for CPU private events James Morse
2017-09-22 18:26 ` [PATCH v3 12/13] arm64: acpi: Remove __init from acpi_psci_use_hvc() for use by SDEI James Morse
2017-09-22 18:26 ` [PATCH v3 13/13] firmware: arm_sdei: Discover SDEI support via ACPI James Morse
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=59E0EEE5.2020208@arm.com \
--to=james.morse@arm$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox