On 7/11/2017 10:38 AM, Brian Gerst wrote: > On Tue, Jul 11, 2017 at 11:02 AM, Tom Lendacky <thomas.lendacky at 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 at 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 at 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 at 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 >
