From: Tom Lendacky <thomas.lendacky@amd.com>
To: Brian Gerst <brgerst@gmail.com>
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Subject: Re: [PATCH v9 07/38] x86/mm: Remove phys_to_virt() usage in ioremap()
Date: Tue, 11 Jul 2017 10:44:34 -0500 [thread overview]
Message-ID: <4404cf23-3b9c-e712-f883-fa6dc4318214@amd.com> (raw)
In-Reply-To: <CAMzpN2i+sqqarshuYJBBNxwP25q_ERezOxRZ-d8+8Ztt=Qm_iw@mail.gmail.com>
On 7/11/2017 10:38 AM, Brian Gerst wrote:
> On Tue, Jul 11, 2017 at 11:02 AM, Tom Lendacky <thomas.lendacky@amd.com> wrote:
>> On 7/10/2017 11:58 PM, Brian Gerst wrote:
>>>
>>> On Mon, Jul 10, 2017 at 3:50 PM, Tom Lendacky <thomas.lendacky@amd.com>
>>> wrote:
>>>>
>>>> On 7/8/2017 7:57 AM, Brian Gerst wrote:
>>>>>
>>>>>
>>>>> On Fri, Jul 7, 2017 at 9:39 AM, Tom Lendacky <thomas.lendacky@amd.com>
>>>>> wrote:
>>>>>>
>>>>>>
>>>>>> Currently there is a check if the address being mapped is in the ISA
>>>>>> range (is_ISA_range()), and if it is, then phys_to_virt() is used to
>>>>>> perform the mapping. When SME is active, the default is to add
>>>>>> pagetable
>>>>>> mappings with the encryption bit set unless specifically overridden.
>>>>>> The
>>>>>> resulting pagetable mapping from phys_to_virt() will result in a
>>>>>> mapping
>>>>>> that has the encryption bit set. With SME, the use of ioremap() is
>>>>>> intended to generate pagetable mappings that do not have the encryption
>>>>>> bit set through the use of the PAGE_KERNEL_IO protection value.
>>>>>>
>>>>>> Rather than special case the SME scenario, remove the ISA range check
>>>>>> and
>>>>>> usage of phys_to_virt() and have ISA range mappings continue through
>>>>>> the
>>>>>> remaining ioremap() path.
>>>>>>
>>>>>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>>>>>> ---
>>>>>> arch/x86/mm/ioremap.c | 7 +------
>>>>>> 1 file changed, 1 insertion(+), 6 deletions(-)
>>>>>>
>>>>>> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
>>>>>> index 4c1b5fd..bfc3e2d 100644
>>>>>> --- a/arch/x86/mm/ioremap.c
>>>>>> +++ b/arch/x86/mm/ioremap.c
>>>>>> @@ -13,6 +13,7 @@
>>>>>> #include <linux/slab.h>
>>>>>> #include <linux/vmalloc.h>
>>>>>> #include <linux/mmiotrace.h>
>>>>>> +#include <linux/mem_encrypt.h>
>>>>>>
>>>>>> #include <asm/set_memory.h>
>>>>>> #include <asm/e820/api.h>
>>>>>> @@ -106,12 +107,6 @@ static void __iomem
>>>>>> *__ioremap_caller(resource_size_t phys_addr,
>>>>>> }
>>>>>>
>>>>>> /*
>>>>>> - * Don't remap the low PCI/ISA area, it's always mapped..
>>>>>> - */
>>>>>> - if (is_ISA_range(phys_addr, last_addr))
>>>>>> - return (__force void __iomem *)phys_to_virt(phys_addr);
>>>>>> -
>>>>>> - /*
>>>>>> * Don't allow anybody to remap normal RAM that we're using..
>>>>>> */
>>>>>> pfn = phys_addr >> PAGE_SHIFT;
>>>>>>
>>>>>
>>>>> Removing this also affects 32-bit, which is more likely to access
>>>>> legacy devices in this range. Put in a check for SME instead
>>>>
>>>>
>>>>
>>>> I originally had a check for SME here in a previous version of the
>>>> patch. Thomas Gleixner recommended removing the check so that the code
>>>> path was always exercised regardless of the state of SME in order to
>>>> better detect issues:
>>>>
>>>> http://marc.info/?l=linux-kernel&m=149803067811436&w=2
>>>>
>>>> Thanks,
>>>> Tom
>>>
>>>
>>> Looking a bit closer, this shortcut doesn't set the caching
>>> attributes. So it's probably best to get rid of it anyways. Also
>>> note, there is a corresponding check in iounmap().
>>
>>
>> Good catch. I'll update the patch to include the removal of the ISA
>> checks in the iounmap() path as well.
>
> I now think it should be kept but also emit a warning, at least for
> the short term. There is bad code out there (vga16fb for example)
> that calls iounmap() blindly without calling ioremap() first. We
> don't want to actually follow through with the unmap on the linear
> mapping.
Yup, was just about to reply to the other email on this. That makes
sense, keep the check but add a warning to it so that it will catch
any misuses of iounmap() and those can then be addressed.
Thanks,
Tom
>
> --
> Brian Gerst
>
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next prev parent reply other threads:[~2017-07-11 15:44 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-07 13:38 [PATCH v9 00/38] x86: Secure Memory Encryption (AMD) Tom Lendacky
2017-07-07 13:38 ` [PATCH v9 01/38] x86: Document AMD Secure Memory Encryption (SME) Tom Lendacky
2017-07-07 13:38 ` [PATCH v9 02/38] x86/mm/pat: Set write-protect cache mode for full PAT support Tom Lendacky
2017-07-07 13:38 ` [PATCH v9 03/38] x86, mpparse, x86/acpi, x86/PCI, x86/dmi, SFI: Use memremap for RAM mappings Tom Lendacky
2017-07-07 13:38 ` [PATCH v9 04/38] x86/CPU/AMD: Add the Secure Memory Encryption CPU feature Tom Lendacky
2017-07-08 12:50 ` Brian Gerst
2017-07-10 19:41 ` Tom Lendacky
2017-07-11 5:07 ` Brian Gerst
2017-07-11 5:56 ` Borislav Petkov
2017-07-11 15:14 ` Tom Lendacky
2017-07-11 15:12 ` Tom Lendacky
2017-07-07 13:39 ` [PATCH v9 05/38] x86/CPU/AMD: Handle SME reduction in physical address size Tom Lendacky
2017-07-07 13:39 ` [PATCH v9 06/38] x86/mm: Add Secure Memory Encryption (SME) support Tom Lendacky
2017-07-07 13:39 ` [PATCH v9 07/38] x86/mm: Remove phys_to_virt() usage in ioremap() Tom Lendacky
2017-07-08 12:57 ` Brian Gerst
2017-07-10 19:50 ` Tom Lendacky
2017-07-11 4:58 ` Brian Gerst
2017-07-11 8:35 ` Arnd Bergmann
2017-07-11 12:00 ` Brian Gerst
2017-07-11 15:02 ` Tom Lendacky
2017-07-11 15:38 ` Brian Gerst
2017-07-11 15:44 ` Tom Lendacky [this message]
2017-07-07 13:39 ` [PATCH v9 08/38] x86/mm: Add support to enable SME in early boot processing Tom Lendacky
2017-07-07 13:39 ` [PATCH v9 09/38] x86/mm: Simplify p[g4um]d_page() macros Tom Lendacky
2017-07-07 13:39 ` [PATCH v9 10/38] x86/mm: Provide general kernel support for memory encryption Tom Lendacky
2017-07-07 13:40 ` [PATCH v9 11/38] x86/mm: Add SME support for read_cr3_pa() Tom Lendacky
2017-07-07 13:40 ` [PATCH v9 12/38] x86/mm: Extend early_memremap() support with additional attrs Tom Lendacky
2017-07-07 13:40 ` [PATCH v9 13/38] x86/mm: Add support for early encrypt/decrypt of memory Tom Lendacky
2017-07-07 13:40 ` [PATCH v9 14/38] x86/mm: Insure that boot memory areas are mapped properly Tom Lendacky
2017-07-07 13:40 ` [PATCH v9 15/38] x86/boot/e820: Add support to determine the E820 type of an address Tom Lendacky
2017-07-07 13:41 ` [PATCH v9 16/38] efi: Add an EFI table address match function Tom Lendacky
2017-07-07 13:41 ` [PATCH v9 17/38] efi: Update efi_mem_type() to return an error rather than 0 Tom Lendacky
2017-07-07 13:41 ` [PATCH v9 18/38] x86/efi: Update EFI pagetable creation to work with SME Tom Lendacky
2017-07-07 13:41 ` [PATCH v9 19/38] x86/mm: Add support to access boot related data in the clear Tom Lendacky
2017-07-07 13:41 ` [PATCH v9 20/38] x86, mpparse: Use memremap to map the mpf and mpc data Tom Lendacky
2017-07-07 13:41 ` [PATCH v9 21/38] x86/mm: Add support to access persistent memory in the clear Tom Lendacky
2017-07-07 13:42 ` [PATCH v9 22/38] x86/mm: Add support for changing the memory encryption attribute Tom Lendacky
2017-07-07 13:42 ` [PATCH v9 23/38] x86/realmode: Decrypt trampoline area if memory encryption is active Tom Lendacky
2017-07-07 13:42 ` [PATCH v9 24/38] x86, swiotlb: Add memory encryption support Tom Lendacky
2017-07-07 13:42 ` [PATCH v9 25/38] swiotlb: Add warnings for use of bounce buffers with SME Tom Lendacky
2017-07-07 13:42 ` [PATCH v9 26/38] x86/CPU/AMD: Make the microcode level available earlier in the boot Tom Lendacky
2017-07-07 13:43 ` [PATCH v9 27/38] iommu/amd: Allow the AMD IOMMU to work with memory encryption Tom Lendacky
2017-07-07 13:43 ` [PATCH v9 28/38] x86, realmode: Check for memory encryption on the APs Tom Lendacky
2017-07-07 13:43 ` [PATCH v9 29/38] x86, drm, fbdev: Do not specify encrypted memory for video mappings Tom Lendacky
2017-07-07 13:43 ` [PATCH v9 30/38] kvm: x86: svm: Support Secure Memory Encryption within KVM Tom Lendacky
2017-07-07 13:43 ` [PATCH v9 31/38] x86/mm, kexec: Allow kexec to be used with SME Tom Lendacky
2017-07-07 13:44 ` [PATCH v9 32/38] xen/x86: Remove SME feature in PV guests Tom Lendacky
2017-07-07 13:44 ` [PATCH v9 33/38] x86/mm: Use proper encryption attributes with /dev/mem Tom Lendacky
2017-07-07 13:44 ` [PATCH v9 34/38] x86/mm: Create native_make_p4d() for PGTABLE_LEVELS <= 4 Tom Lendacky
2017-07-07 13:44 ` [PATCH v9 35/38] x86/mm: Add support to encrypt the kernel in-place Tom Lendacky
2017-07-07 13:44 ` [PATCH v9 36/38] x86/boot: Add early cmdline parsing for options with arguments Tom Lendacky
2017-07-07 13:45 ` [PATCH v9 37/38] compiler-gcc.h: Introduce __nostackp function attribute Tom Lendacky
2017-07-07 13:45 ` [PATCH v9 38/38] x86/mm: Add support to make use of Secure Memory Encryption Tom Lendacky
2017-07-08 9:24 ` [PATCH v9 00/38] x86: Secure Memory Encryption (AMD) Ingo Molnar
2017-07-10 18:04 ` Tom Lendacky
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