From: Dave Hansen <dave.hansen@intel.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "Rafael J. Wysocki" <rafael@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Adrian Hunter <adrian.hunter@intel.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>,
Elena Reshetova <elena.reshetova@intel.com>,
Jun Nakajima <jun.nakajima@intel.com>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
"Kalra, Ashish" <ashish.kalra@amd.com>,
Sean Christopherson <seanjc@google.com>,
"Huang, Kai" <kai.huang@intel.com>, Baoquan He <bhe@redhat.com>,
kexec@lists.infradead.org, linux-coco@lists.linux.dev,
linux-kernel@vger.kernel.org
Subject: Re: [PATCHv7 10/16] x86/tdx: Convert shared memory back to private on kexec
Date: Mon, 26 Feb 2024 05:58:23 -0800 [thread overview]
Message-ID: <0b70ee1e-4bb5-4867-9378-f5723ca091d5@intel.com> (raw)
In-Reply-To: <3nqc34o54ydpdvo6j7a5hltyjs6kkw5jy5i6dgvivg7f4hzec2@l6jetcopnm6k>
On 2/25/24 06:58, Kirill A. Shutemov wrote:
> On Fri, Feb 23, 2024 at 11:39:07AM -0800, Dave Hansen wrote:
...
>> I'd really prefer we find a way to do this with actual locks, especially
>> 'conversion_allowed'.
>>
>> This is _awfully_ close to being able to be handled by a rwsem where the
>> readers are the converters and tdx_kexec_stop_conversion() takes a write.
>
> Okay, here's what I come up with. It needs more testing.
>
> Any comments?
Looks a heck of a lot more straightforward to me.
> +static void tdx_kexec_stop_conversion(bool crash)
> +{
> + /* Stop new private<->shared conversions */
> + if (!stop_memory_enc_conversion(!crash))
> + pr_warn("Failed to finish shared<->private conversions\n");
> +}
FWIW, this is one of those places that could use a temporary variable to
help explain what is going on:
bool wait_for_lock = !crash;
/*
* ... explain why it doesn't or shouldn't take the lock here
*/
if (!stop_memory_enc_conversion(wait_for_lock))
...
This makes it understandable without looking at the called function.
> +bool stop_memory_enc_conversion(bool wait)
> +{
> + if (!wait)
> + return down_write_trylock(&mem_enc_lock);
> +
> + down_write(&mem_enc_lock);
> +
> + return true;
> +}
This also needs a comment about why the lock isn't being released.
next prev parent reply other threads:[~2024-02-26 13:58 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-12 10:44 [PATCHv7 00/16] x86/tdx: Add kexec support Kirill A. Shutemov
2024-02-12 10:44 ` [PATCHv7 01/16] x86/acpi: Extract ACPI MADT wakeup code into a separate file Kirill A. Shutemov
2024-02-19 4:45 ` Baoquan He
2024-02-19 10:08 ` Kirill A. Shutemov
2024-02-19 11:36 ` Baoquan He
2024-02-23 10:32 ` Thomas Gleixner
2024-02-12 10:44 ` [PATCHv7 02/16] x86/apic: Mark acpi_mp_wake_* variables as __ro_after_init Kirill A. Shutemov
2024-02-19 4:46 ` Baoquan He
2024-02-23 10:31 ` Thomas Gleixner
2024-02-12 10:44 ` [PATCHv7 03/16] cpu/hotplug: Add support for declaring CPU offlining not supported Kirill A. Shutemov
2024-02-12 10:44 ` [PATCHv7 04/16] cpu/hotplug, x86/acpi: Disable CPU offlining for ACPI MADT wakeup Kirill A. Shutemov
2024-02-12 10:44 ` [PATCHv7 05/16] x86/kexec: Keep CR4.MCE set during kexec for TDX guest Kirill A. Shutemov
2024-02-22 22:04 ` Thomas Gleixner
2024-02-12 10:44 ` [PATCHv7 06/16] x86/mm: Make x86_platform.guest.enc_status_change_*() return errno Kirill A. Shutemov
2024-02-23 18:26 ` Dave Hansen
2024-02-12 10:44 ` [PATCHv7 07/16] x86/mm: Return correct level from lookup_address() if pte is none Kirill A. Shutemov
2024-02-19 5:12 ` Baoquan He
2024-02-19 13:52 ` Kirill A. Shutemov
2024-02-20 10:25 ` Baoquan He
2024-02-20 12:36 ` Kirill A. Shutemov
2024-02-21 2:37 ` Baoquan He
2024-02-21 14:15 ` Kirill A. Shutemov
2024-02-22 11:01 ` Baoquan He
2024-02-22 14:04 ` Kirill A. Shutemov
2024-02-22 15:37 ` Baoquan He
2024-02-23 18:45 ` Dave Hansen
2024-02-23 18:58 ` Dave Hansen
2024-02-12 10:44 ` [PATCHv7 08/16] x86/tdx: Account shared memory Kirill A. Shutemov
2024-02-23 19:08 ` Dave Hansen
2024-02-25 15:54 ` Kirill A. Shutemov
2024-02-25 17:34 ` Dave Hansen
2024-02-12 10:44 ` [PATCHv7 09/16] x86/mm: Adding callbacks to prepare encrypted memory for kexec Kirill A. Shutemov
2024-02-12 10:44 ` [PATCHv7 10/16] x86/tdx: Convert shared memory back to private on kexec Kirill A. Shutemov
2024-02-23 19:39 ` Dave Hansen
2024-02-25 14:58 ` Kirill A. Shutemov
2024-02-26 13:10 ` Kirill A. Shutemov
2024-02-26 13:58 ` Dave Hansen [this message]
2024-02-12 10:44 ` [PATCHv7 11/16] x86/mm: Make e820_end_ram_pfn() cover E820_TYPE_ACPI ranges Kirill A. Shutemov
2024-02-23 19:41 ` Dave Hansen
2024-02-12 10:44 ` [PATCHv7 12/16] x86/acpi: Rename fields in acpi_madt_multiproc_wakeup structure Kirill A. Shutemov
2024-02-23 10:27 ` Thomas Gleixner
2024-02-12 10:44 ` [PATCHv7 13/16] x86/acpi: Do not attempt to bring up secondary CPUs in kexec case Kirill A. Shutemov
2024-02-23 10:28 ` Thomas Gleixner
2024-02-12 10:44 ` [PATCHv7 14/16] x86/smp: Add smp_ops.stop_this_cpu() callback Kirill A. Shutemov
2024-02-23 10:26 ` Thomas Gleixner
2024-02-12 10:44 ` [PATCHv7 15/16] x86/mm: Introduce kernel_ident_mapping_free() Kirill A. Shutemov
2024-02-12 10:44 ` [PATCHv7 16/16] x86/acpi: Add support for CPU offlining for ACPI MADT wakeup method Kirill A. Shutemov
2024-02-23 10:31 ` Thomas Gleixner
2024-02-20 1:18 ` [PATCH 0/2] x86/snp: Add kexec support Ashish Kalra
2024-02-20 1:18 ` [PATCH 1/2] x86/mm: Do not zap PMD entry mapping unaccepted memory table during kdump Ashish Kalra
2024-02-20 12:42 ` Kirill A. Shutemov
2024-02-20 19:09 ` Kalra, Ashish
2024-02-20 1:18 ` [PATCH 2/2] x86/snp: Convert shared memory back to private on kexec Ashish Kalra
2024-02-21 20:35 ` Tom Lendacky
2024-02-22 10:50 ` Kirill A. Shutemov
2024-02-22 13:58 ` Tom Lendacky
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