From: Ankit Agrawal <ankita@xxxxxxxxxx> Generalizing S2 setting from DEVICE_nGnRE to NormalNc for non PCI devices may be problematic. E.g. GICv2 vCPU interface, which is effectively a shared peripheral, can allow a guest to affect another guest's interrupt distribution. The issue may be solved by limiting the relaxation to mappings that have a user VMA. Still there is insufficient information and uncertainity in the behavior of non PCI drivers. Add a new flag VM_ALLOW_ANY_UNCACHED to indicate KVM that the device is WC capable and these S2 changes can be extended to it. KVM can use this flag to activate the code. Suggested-by: Catalin Marinas <catalin.marinas@xxxxxxx> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Signed-off-by: Ankit Agrawal <ankita@xxxxxxxxxx> --- include/linux/mm.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index f5a97dec5169..59576e56c58b 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -391,6 +391,20 @@ extern unsigned int kobjsize(const void *objp); # define VM_UFFD_MINOR VM_NONE #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */ +/* + * This flag is used to connect VFIO to arch specific KVM code. It + * indicates that the memory under this VMA is safe for use with any + * non-cachable memory type inside KVM. Some VFIO devices, on some + * platforms, are thought to be unsafe and can cause machine crashes + * if KVM does not lock down the memory type. + */ +#ifdef CONFIG_64BIT +#define VM_ALLOW_ANY_UNCACHED_BIT 39 +#define VM_ALLOW_ANY_UNCACHED BIT(VM_ALLOW_ANY_UNCACHED_BIT) +#else +#define VM_ALLOW_ANY_UNCACHED VM_NONE +#endif + /* Bits set in the VMA until the stack is in its final location */ #define VM_STACK_INCOMPLETE_SETUP (VM_RAND_READ | VM_SEQ_READ | VM_STACK_EARLY) -- 2.34.1
