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Message-ID: <20171106024143.GA3669@x1>
Date: Mon, 6 Nov 2017 10:41:43 +0800
From: Baoquan He <bhe@...hat.com>
To: Jiri Bohac <jbohac@...e.cz>
Cc: David Airlie <airlied@...ux.ie>, Dave Young <dyoung@...hat.com>,
Vivek Goyal <vgoyal@...hat.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Toshi Kani <toshi.kani@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
kexec@...ts.infradead.org, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH] x86/kexec: Exclude GART aperture from vmcore
Hi Jiri,
On 11/03/17 at 06:28pm, Jiri Bohac wrote:
> On machines where the GART aperture is mapped over physical RAM
> /proc/vmcore contains the remapped range and reading it may
> cause hangs or reboots. This range needs to be excluded from /proc/vmcore.
>
> This has originally been implemented by commit dd5f726076cc ("kexec:
> support for kexec on panic using new system call").
>
> The implementation relied on the GART code adding an iomem_resource for
> this range called "GART", as implemented by commit 56dd669a138c ("[PATCH]
> Insert GART region into resource map")
>
> However, inserting the iomem_resource from the early GART code caused
> resource conflicts with some AGP drivers (bko#72201), which got avoided by
> reverting the patch in commit 707d4eefbdb3 ("Revert [PATCH] Insert GART
> region into resource map"). This revert introduced the /proc/vmcore bug.
>
> With the "GART" iomem_resource removed, the defunct code in crash.c has
> been removed by commit f296f2634920 ("x86/kexec: Remove walk_iomem_res()
> call with GART type")
Is this reproduced on a machine with GART existing and passing test with
this patch applied? Do you have a /proc/iomem printing about the machine
you are testing on?
If this patch works, then I am wondering how we shold deal with the old
way in which no '-s' is specified. Since no GART information is exported
to /proc/iomem.
Do we have a way to pick GART region away from iomem_resource to not let
the aperture seen from /proc/iomem?
Thanks
Baoquan
>
> The patch below stores the location of the GART region in two variables
> (named gart_stolen_ram_start and gart_stolen_ram_end) and reverts/adapts
> parts of f296f2634920 to exclude the region from /proc/vmcore.
>
> Passing the information via an iomem_resource (or by reserving the range
> in the e820, which would propagate into an iomem_resource) would
> reintroduce bko#72201.
>
> Signed-off-by: Jiri Bohac <jbohac@...e.cz>
> Fixes: 707d4eefbdb3 ("Revert [PATCH] Insert GART region into resource map")
>
> diff --git a/arch/x86/include/asm/gart.h b/arch/x86/include/asm/gart.h
> index 1d268098ac2e..324a0a19d166 100644
> --- a/arch/x86/include/asm/gart.h
> +++ b/arch/x86/include/asm/gart.h
> @@ -2,6 +2,7 @@
> #define _ASM_X86_GART_H
>
> #include <asm/e820/api.h>
> +#include <linux/pci.h>
>
> extern void set_up_gart_resume(u32, u32);
>
> @@ -33,6 +34,8 @@ extern int fix_aperture;
> extern int gart_iommu_aperture;
> extern int gart_iommu_aperture_allowed;
> extern int gart_iommu_aperture_disabled;
> +extern u32 gart_stolen_ram_start;
> +extern u32 gart_stolen_ram_end;
>
> extern void early_gart_iommu_check(void);
> extern int gart_iommu_init(void);
> @@ -43,6 +46,8 @@ extern int gart_iommu_hole_init(void);
> #define gart_iommu_aperture 0
> #define gart_iommu_aperture_allowed 0
> #define gart_iommu_aperture_disabled 1
> +#define gart_stolen_ram_start 0
> +#define gart_stolen_ram_end 0
>
> static inline void early_gart_iommu_check(void)
> {
> diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c
> index ef2859f9fcce..bc9a9b5b88e3 100644
> --- a/arch/x86/kernel/aperture_64.c
> +++ b/arch/x86/kernel/aperture_64.c
> @@ -49,6 +49,8 @@
> int gart_iommu_aperture;
> int gart_iommu_aperture_disabled __initdata;
> int gart_iommu_aperture_allowed __initdata;
> +u32 gart_stolen_ram_start;
> +u32 gart_stolen_ram_end;
>
> int fallback_aper_order __initdata = 1; /* 64MB */
> int fallback_aper_force __initdata;
> @@ -87,6 +89,9 @@ static u32 __init allocate_aperture(void)
> register_nosave_region(addr >> PAGE_SHIFT,
> (addr+aper_size) >> PAGE_SHIFT);
>
> + gart_stolen_ram_start = (u32)addr;
> + gart_stolen_ram_end = (u32)addr + aper_size - 1;
> +
> return (u32)addr;
> }
>
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 44404e2307bb..ce065d72656d 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -37,6 +37,7 @@
> #include <asm/reboot.h>
> #include <asm/virtext.h>
> #include <asm/intel_pt.h>
> +#include <asm/gart.h>
>
> /* Alignment required for elf header segment */
> #define ELF_CORE_HEADER_ALIGN 4096
> @@ -58,7 +59,7 @@ struct crash_elf_data {
> struct kimage *image;
> /*
> * Total number of ram ranges we have after various adjustments for
> - * crash reserved region, etc.
> + * GART, crash reserved region etc.
> */
> unsigned int max_nr_ranges;
>
> @@ -217,7 +218,6 @@ static int get_nr_ram_ranges_callback(u64 start, u64 end, void *arg)
> return 0;
> }
>
> -
> /* Gather all the required information to prepare elf headers for ram regions */
> static void fill_up_crash_elf_data(struct crash_elf_data *ced,
> struct kimage *image)
> @@ -231,6 +231,15 @@ static void fill_up_crash_elf_data(struct crash_elf_data *ced,
>
> ced->max_nr_ranges = nr_ranges;
>
> + /*
> + * We don't create ELF headers for GART aperture as an attempt
> + * to dump this memory in second kernel leads to hang/crash.
> + * If gart aperture is mapped over RAM, one needs to exclude that region
> + * and that requires an extra phdr.
> + */
> + if (gart_stolen_ram_start)
> + ced->max_nr_ranges++;
> +
> /* Exclusion of crash region could split memory ranges */
> ced->max_nr_ranges++;
>
> @@ -339,6 +348,14 @@ static int elf_header_exclude_ranges(struct crash_elf_data *ced,
> return ret;
> }
>
> + /* Exclude GART region */
> + if (gart_stolen_ram_start) {
> + ret = exclude_mem_range(cmem, gart_stolen_ram_start,
> + gart_stolen_ram_end);
> + if (ret)
> + return ret;
> + }
> +
> return ret;
> }
>
> --
> Jiri Bohac <jbohac@...e.cz>
> SUSE Labs, Prague, Czechia
>
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