linux-kernel - Re: [PATCH 1/4] ACPICA: Do not flush cache for on entering S4 and S5

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Date:   Wed, 8 Dec 2021 15:58:26 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Robert Moore <robert.moore@...el.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tony Luck <tony.luck@...el.com>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH 1/4] ACPICA: Do not flush cache for on entering S4 and S5

On Mon, Dec 6, 2021 at 1:30 PM Kirill A. Shutemov
<kirill.shutemov@...ux.intel.com> wrote:
>
> According to the ACPI spec v6.4, section 16.2 the cache flushing is
> required on entering to S1, S2, and S3. ACPICA code flushes cache
> regardless of the sleep state.
>
> Blind cache flush on entering S5 causes problems for TDX. Flushing
> happens with WBINVD that is not supported in the TDX environment.
>
> TDX only supports S5 and adjusting ACPICA code to conform to the spec
> fixes the issue.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

I've converted this patch to the upstream ACPICA code base format and
submitted a pull request with it to the upstream project.

Thanks!

> ---
>  drivers/acpi/acpica/hwesleep.c  | 3 ++-
>  drivers/acpi/acpica/hwsleep.c   | 3 ++-
>  drivers/acpi/acpica/hwxfsleep.c | 2 --
>  3 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/acpi/acpica/hwesleep.c b/drivers/acpi/acpica/hwesleep.c
> index 808fdf54aeeb..ceb5a4292efa 100644
> --- a/drivers/acpi/acpica/hwesleep.c
> +++ b/drivers/acpi/acpica/hwesleep.c
> @@ -104,7 +104,8 @@ acpi_status acpi_hw_extended_sleep(u8 sleep_state)
>
>         /* Flush caches, as per ACPI specification */
>
> -       ACPI_FLUSH_CPU_CACHE();
> +       if (sleep_state < ACPI_STATE_S4)
> +               ACPI_FLUSH_CPU_CACHE();
>
>         status = acpi_os_enter_sleep(sleep_state, sleep_control, 0);
>         if (status == AE_CTRL_TERMINATE) {
> diff --git a/drivers/acpi/acpica/hwsleep.c b/drivers/acpi/acpica/hwsleep.c
> index 34a3825f25d3..ee094a3aaaab 100644
> --- a/drivers/acpi/acpica/hwsleep.c
> +++ b/drivers/acpi/acpica/hwsleep.c
> @@ -110,7 +110,8 @@ acpi_status acpi_hw_legacy_sleep(u8 sleep_state)
>
>         /* Flush caches, as per ACPI specification */
>
> -       ACPI_FLUSH_CPU_CACHE();
> +       if (sleep_state < ACPI_STATE_S4)
> +               ACPI_FLUSH_CPU_CACHE();
>
>         status = acpi_os_enter_sleep(sleep_state, pm1a_control, pm1b_control);
>         if (status == AE_CTRL_TERMINATE) {
> diff --git a/drivers/acpi/acpica/hwxfsleep.c b/drivers/acpi/acpica/hwxfsleep.c
> index e4cde23a2906..ba77598ee43e 100644
> --- a/drivers/acpi/acpica/hwxfsleep.c
> +++ b/drivers/acpi/acpica/hwxfsleep.c
> @@ -162,8 +162,6 @@ acpi_status acpi_enter_sleep_state_s4bios(void)
>                 return_ACPI_STATUS(status);
>         }
>
> -       ACPI_FLUSH_CPU_CACHE();
> -
>         status = acpi_hw_write_port(acpi_gbl_FADT.smi_command,
>                                     (u32)acpi_gbl_FADT.s4_bios_request, 8);
>         if (ACPI_FAILURE(status)) {
> --
> 2.32.0
>