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Message-ID: <BY3PR18MB46927A33E493191AA4F23B03D4ABA@BY3PR18MB4692.namprd18.prod.outlook.com>
Date: Sun, 5 Nov 2023 15:25:29 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Abhinav Singh <singhabhinav9051571833@...il.com>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"bp@...en8.de" <bp@...en8.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"decui@...rosoft.com" <decui@...rosoft.com>,
"wei.liu@...nel.org" <wei.liu@...nel.org>,
"haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
"kys@...rosoft.com" <kys@...rosoft.com>,
"niyelchu@...ux.microsoft.com" <niyelchu@...ux.microsoft.com>
Subject: RE: [PATCH v2] x86/hyperv : Fixing removal of __iomem address space
warning
From: Abhinav Singh <singhabhinav9051571833@...il.com> Sent: Monday, October 30, 2023 3:50 PM
>
> This patch fixes two sparse warnings
>
> 1. sparse complaining about the removal of __iomem address
> space when casting the return value of this ioremap_cache(...)
> from `void __ioremap*` to `void*`.
> Fixed this by replacing the ioremap_cache(...)
> by memremap(...) and using MEMREMAP_DEC and MEMREMAP_WB flag for
> making
> sure the memory is always decrypted and it will support full write back
> cache.
>
> 2. sparse complaining `expected void volatile [noderef] __iomem *addr`
> when calling iounmap with a non __iomem pointer.
> Fixed this by replacing iounmap(...) with memumap(...).
>
> Signed-off-by: Abhinav Singh <singhabhinav9051571833@...il.com>
Since Nischala has posted her more comprehensive patch,
this patch can be dropped. But see one comment below for
future reference.
> ---
>
> v1:
> https://lore.kernel.org/all/19cec6f0-e176-4bcc-95a0-9d6eb0261ed1@gmail.com/T/
>
> v1 to v2:
> 1. Fixed the comment which was earlier describing ioremap_cache(...).
> 2. Replaced iounmap(...) with memremap(...) inside function hv_cpu_die(...).
>
> arch/x86/hyperv/hv_init.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 21556ad87f4b..2a14928b8a36 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -68,9 +68,11 @@ static int hyperv_init_ghcb(void)
> */
> rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
>
> - /* Mask out vTOM bit. ioremap_cache() maps decrypted */
> + /* Mask out vTOM bit.
> + MEMREMAP_WB full write back cache
> + MEMREMAP_DEC maps decrypted memory */
This isn't the right style for multi-line patches. Correct would be:
/*
* Mask out vTOM bit.
* MEMREMAP_WB full write back cache
* MEMREMAP_DEC maps decrypted memory
*/
Section 8 of coding-style.rst under Documentation/process covers
these details. Note that the style is slightly different for code
under net and drivers/net.
Michael
> ghcb_gpa &= ~ms_hyperv.shared_gpa_boundary;
> - ghcb_va = (void *)ioremap_cache(ghcb_gpa, HV_HYP_PAGE_SIZE);
> + ghcb_va = memremap(ghcb_gpa, HV_HYP_PAGE_SIZE, MEMREMAP_WB | MEMREMAP_DEC);
> if (!ghcb_va)
> return -ENOMEM;
>
> @@ -238,7 +240,7 @@ static int hv_cpu_die(unsigned int cpu)
> if (hv_ghcb_pg) {
> ghcb_va = (void **)this_cpu_ptr(hv_ghcb_pg);
> if (*ghcb_va)
> - iounmap(*ghcb_va);
> + memunmap(*ghcb_va);
> *ghcb_va = NULL;
> }
>
> --
> 2.39.2
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